move syntax highlighting to separate crate

Cargo.lock

@@ -1311,6 +1311,7 @@ dependencies = [
  "hashbrown 0.14.5",
  "helix-loader",
  "helix-stdx",
+ "helix-syntax",
  "imara-diff",
  "indoc",
  "log",
@@ -1425,6 +1426,23 @@ dependencies = [
  "windows-sys 0.52.0",
 ]
 
+[[package]]
+name = "helix-syntax"
+version = "24.7.0"
+dependencies = [
+ "ahash",
+ "arc-swap",
+ "bitflags 2.6.0",
+ "hashbrown 0.14.5",
+ "helix-stdx",
+ "log",
+ "once_cell",
+ "regex",
+ "ropey",
+ "slotmap",
+ "tree-sitter",
+]
+
 [[package]]
 name = "helix-term"
 version = "24.7.0"

Cargo.toml

@@ -12,6 +12,7 @@ members = [
   "helix-vcs",
   "helix-parsec",
   "helix-stdx",
+  "helix-syntax",
   "xtask",
 ]
 

helix-core/Cargo.toml

@@ -17,6 +17,7 @@ integration = []
 
 [dependencies]
 helix-stdx = { path = "../helix-stdx" }
+helix-syntax = { path = "../helix-syntax" }
 helix-loader = { path = "../helix-loader" }
 
 ropey = { version = "1.6.1", default-features = false, features = ["simd"] }

helix-core/src/indent.rs

@@ -738,18 +738,9 @@ fn init_indent_query<'a, 'b>(
             .map(|prec| prec.byte_range().end - 1..byte_pos + 1)
             .unwrap_or(byte_pos..byte_pos + 1);
 
-        crate::syntax::PARSER.with(|ts_parser| {
+        crate::syntax::with_cursor(|cursor| {
-            let mut ts_parser = ts_parser.borrow_mut();
+            let query_result =
-            let mut cursor = ts_parser.cursors.pop().unwrap_or_default();
+                query_indents(query, syntax, cursor, text, query_range, new_line_byte_pos);
-            let query_result = query_indents(
-                query,
-                syntax,
-                &mut cursor,
-                text,
-                query_range,
-                new_line_byte_pos,
-            );
-            ts_parser.cursors.push(cursor);
             (query_result, deepest_preceding)
         })
     };

helix-core/tests/indent.rs

@@ -1,4 +1,3 @@
-use arc_swap::ArcSwap;
 use helix_core::{
     indent::{indent_level_for_line, treesitter_indent_for_pos, IndentStyle},
     syntax::{Configuration, Loader},
@@ -6,7 +5,7 @@
 };
 use helix_stdx::rope::RopeSliceExt;
 use ropey::Rope;
-use std::{ops::Range, path::PathBuf, process::Command, sync::Arc};
+use std::{ops::Range, path::PathBuf, process::Command};
 
 #[test]
 fn test_treesitter_indent_rust() {
@@ -200,12 +199,7 @@ fn test_treesitter_indent(
     let indent_style = IndentStyle::from_str(&language_config.indent.as_ref().unwrap().unit);
     let highlight_config = language_config.highlight_config(&[]).unwrap();
     let text = doc.slice(..);
-    let syntax = Syntax::new(
+    let syntax = Syntax::new(text, highlight_config, |_| None).unwrap();
-        text,
-        highlight_config,
-        Arc::new(ArcSwap::from_pointee(loader)),
-    )
-    .unwrap();
     let indent_query = language_config.indent_query().unwrap();
 
     for i in 0..doc.len_lines() {

helix-syntax/Cargo.toml

@@ -0,0 +1,28 @@
+[package]
+name = "helix-syntax"
+description = "Helix syntax highlighting "
+include = ["src/**/*", "README.md"]
+version.workspace = true
+authors.workspace = true
+edition.workspace = true
+license.workspace = true
+rust-version.workspace = true
+categories.workspace = true
+repository.workspace = true
+homepage.workspace = true
+
+[features]
+
+[dependencies]
+helix-stdx = { path = "../helix-stdx" }
+
+ropey = { version = "1.6.1", default-features = false, features = ["simd"] }
+slotmap = "1.0"
+tree-sitter.workspace = true
+once_cell = "1.19"
+arc-swap = "1"
+regex = "1"
+bitflags = "2.4"
+ahash = "0.8.9"
+hashbrown = { version = "0.14.3", features = ["raw"] }
+log = "0.4"

helix-syntax/src/config.rs

@@ -0,0 +1,331 @@
+use std::path::Path;
+use std::sync::Arc;
+
+use arc_swap::ArcSwap;
+use helix_stdx::rope::{self, RopeSliceExt};
+use once_cell::sync::Lazy;
+use regex::Regex;
+use ropey::RopeSlice;
+use tree_sitter::{Language as Grammar, Node, Query, QueryError, QueryMatch};
+
+use crate::highlighter::Highlight;
+use crate::{byte_range_to_str, IncludedChildren, InjectionLanguageMarker, SHEBANG};
+
+/// Contains the data needed to highlight code written in a particular language.
+///
+/// This struct is immutable and can be shared between threads.
+#[derive(Debug)]
+pub struct HighlightConfiguration {
+    pub language: Grammar,
+    pub query: Query,
+    pub(crate) injections_query: Query,
+    pub(crate) combined_injections_patterns: Vec<usize>,
+    pub(crate) highlights_pattern_index: usize,
+    pub(crate) highlight_indices: ArcSwap<Vec<Option<Highlight>>>,
+    pub(crate) non_local_variable_patterns: Vec<bool>,
+    pub(crate) injection_content_capture_index: Option<u32>,
+    pub(crate) injection_language_capture_index: Option<u32>,
+    pub(crate) injection_filename_capture_index: Option<u32>,
+    pub(crate) injection_shebang_capture_index: Option<u32>,
+    pub(crate) local_scope_capture_index: Option<u32>,
+    pub(crate) local_def_capture_index: Option<u32>,
+    pub(crate) local_def_value_capture_index: Option<u32>,
+    pub(crate) local_ref_capture_index: Option<u32>,
+}
+
+impl HighlightConfiguration {
+    /// Creates a `HighlightConfiguration` for a given `Grammar` and set of highlighting
+    /// queries.
+    ///
+    /// # Parameters
+    ///
+    /// * `language`  - The Tree-sitter `Grammar` that should be used for parsing.
+    /// * `highlights_query` - A string containing tree patterns for syntax highlighting. This
+    ///   should be non-empty, otherwise no syntax highlights will be added.
+    /// * `injections_query` -  A string containing tree patterns for injecting other languages
+    ///   into the document. This can be empty if no injections are desired.
+    /// * `locals_query` - A string containing tree patterns for tracking local variable
+    ///   definitions and references. This can be empty if local variable tracking is not needed.
+    ///
+    /// Returns a `HighlightConfiguration` that can then be used with the `highlight` method.
+    pub fn new(
+        language: Grammar,
+        highlights_query: &str,
+        injection_query: &str,
+        locals_query: &str,
+    ) -> Result<Self, QueryError> {
+        // Concatenate the query strings, keeping track of the start offset of each section.
+        let mut query_source = String::new();
+        query_source.push_str(locals_query);
+        let highlights_query_offset = query_source.len();
+        query_source.push_str(highlights_query);
+
+        // Construct a single query by concatenating the three query strings, but record the
+        // range of pattern indices that belong to each individual string.
+        let query = Query::new(&language, &query_source)?;
+        let mut highlights_pattern_index = 0;
+        for i in 0..(query.pattern_count()) {
+            let pattern_offset = query.start_byte_for_pattern(i);
+            if pattern_offset < highlights_query_offset {
+                highlights_pattern_index += 1;
+            }
+        }
+
+        let injections_query = Query::new(&language, injection_query)?;
+        let combined_injections_patterns = (0..injections_query.pattern_count())
+            .filter(|&i| {
+                injections_query
+                    .property_settings(i)
+                    .iter()
+                    .any(|s| &*s.key == "injection.combined")
+            })
+            .collect();
+
+        // Find all of the highlighting patterns that are disabled for nodes that
+        // have been identified as local variables.
+        let non_local_variable_patterns = (0..query.pattern_count())
+            .map(|i| {
+                query
+                    .property_predicates(i)
+                    .iter()
+                    .any(|(prop, positive)| !*positive && prop.key.as_ref() == "local")
+            })
+            .collect();
+
+        // Store the numeric ids for all of the special captures.
+        let mut injection_content_capture_index = None;
+        let mut injection_language_capture_index = None;
+        let mut injection_filename_capture_index = None;
+        let mut injection_shebang_capture_index = None;
+        let mut local_def_capture_index = None;
+        let mut local_def_value_capture_index = None;
+        let mut local_ref_capture_index = None;
+        let mut local_scope_capture_index = None;
+        for (i, name) in query.capture_names().iter().enumerate() {
+            let i = Some(i as u32);
+            match *name {
+                "local.definition" => local_def_capture_index = i,
+                "local.definition-value" => local_def_value_capture_index = i,
+                "local.reference" => local_ref_capture_index = i,
+                "local.scope" => local_scope_capture_index = i,
+                _ => {}
+            }
+        }
+
+        for (i, name) in injections_query.capture_names().iter().enumerate() {
+            let i = Some(i as u32);
+            match *name {
+                "injection.content" => injection_content_capture_index = i,
+                "injection.language" => injection_language_capture_index = i,
+                "injection.filename" => injection_filename_capture_index = i,
+                "injection.shebang" => injection_shebang_capture_index = i,
+                _ => {}
+            }
+        }
+
+        let highlight_indices = ArcSwap::from_pointee(vec![None; query.capture_names().len()]);
+        Ok(Self {
+            language,
+            query,
+            injections_query,
+            combined_injections_patterns,
+            highlights_pattern_index,
+            highlight_indices,
+            non_local_variable_patterns,
+            injection_content_capture_index,
+            injection_language_capture_index,
+            injection_filename_capture_index,
+            injection_shebang_capture_index,
+            local_scope_capture_index,
+            local_def_capture_index,
+            local_def_value_capture_index,
+            local_ref_capture_index,
+        })
+    }
+
+    /// Get a slice containing all of the highlight names used in the configuration.
+    pub fn names(&self) -> &[&str] {
+        self.query.capture_names()
+    }
+
+    /// Set the list of recognized highlight names.
+    ///
+    /// Tree-sitter syntax-highlighting queries specify highlights in the form of dot-separated
+    /// highlight names like `punctuation.bracket` and `function.method.builtin`. Consumers of
+    /// these queries can choose to recognize highlights with different levels of specificity.
+    /// For example, the string `function.builtin` will match against `function.builtin.constructor`
+    /// but will not match `function.method.builtin` and `function.method`.
+    ///
+    /// When highlighting, results are returned as `Highlight` values, which contain the index
+    /// of the matched highlight this list of highlight names.
+    pub fn configure(&self, recognized_names: &[String]) {
+        let mut capture_parts = Vec::new();
+        let indices: Vec<_> = self
+            .query
+            .capture_names()
+            .iter()
+            .map(move |capture_name| {
+                capture_parts.clear();
+                capture_parts.extend(capture_name.split('.'));
+
+                let mut best_index = None;
+                let mut best_match_len = 0;
+                for (i, recognized_name) in recognized_names.iter().enumerate() {
+                    let mut len = 0;
+                    let mut matches = true;
+                    for (i, part) in recognized_name.split('.').enumerate() {
+                        match capture_parts.get(i) {
+                            Some(capture_part) if *capture_part == part => len += 1,
+                            _ => {
+                                matches = false;
+                                break;
+                            }
+                        }
+                    }
+                    if matches && len > best_match_len {
+                        best_index = Some(i);
+                        best_match_len = len;
+                    }
+                }
+                best_index.map(Highlight)
+            })
+            .collect();
+
+        self.highlight_indices.store(Arc::new(indices));
+    }
+
+    fn injection_pair<'a>(
+        &self,
+        query_match: &QueryMatch<'a, 'a>,
+        source: RopeSlice<'a>,
+    ) -> (Option<InjectionLanguageMarker<'a>>, Option<Node<'a>>) {
+        let mut injection_capture = None;
+        let mut content_node = None;
+
+        for capture in query_match.captures {
+            let index = Some(capture.index);
+            if index == self.injection_language_capture_index {
+                let name = byte_range_to_str(capture.node.byte_range(), source);
+                injection_capture = Some(InjectionLanguageMarker::Name(name));
+            } else if index == self.injection_filename_capture_index {
+                let name = byte_range_to_str(capture.node.byte_range(), source);
+                let path = Path::new(name.as_ref()).to_path_buf();
+                injection_capture = Some(InjectionLanguageMarker::Filename(path.into()));
+            } else if index == self.injection_shebang_capture_index {
+                let node_slice = source.byte_slice(capture.node.byte_range());
+
+                // some languages allow space and newlines before the actual string content
+                // so a shebang could be on either the first or second line
+                let lines = if let Ok(end) = node_slice.try_line_to_byte(2) {
+                    node_slice.byte_slice(..end)
+                } else {
+                    node_slice
+                };
+
+                static SHEBANG_REGEX: Lazy<rope::Regex> =
+                    Lazy::new(|| rope::Regex::new(SHEBANG).unwrap());
+
+                injection_capture = SHEBANG_REGEX
+                    .captures_iter(lines.regex_input())
+                    .map(|cap| {
+                        let cap = lines.byte_slice(cap.get_group(1).unwrap().range());
+                        InjectionLanguageMarker::Shebang(cap.into())
+                    })
+                    .next()
+            } else if index == self.injection_content_capture_index {
+                content_node = Some(capture.node);
+            }
+        }
+        (injection_capture, content_node)
+    }
+
+    pub(super) fn injection_for_match<'a>(
+        &self,
+        query: &'a Query,
+        query_match: &QueryMatch<'a, 'a>,
+        source: RopeSlice<'a>,
+    ) -> (
+        Option<InjectionLanguageMarker<'a>>,
+        Option<Node<'a>>,
+        IncludedChildren,
+    ) {
+        let (mut injection_capture, content_node) = self.injection_pair(query_match, source);
+
+        let mut included_children = IncludedChildren::default();
+        for prop in query.property_settings(query_match.pattern_index) {
+            match prop.key.as_ref() {
+                // In addition to specifying the language name via the text of a
+                // captured node, it can also be hard-coded via a `#set!` predicate
+                // that sets the injection.language key.
+                "injection.language" if injection_capture.is_none() => {
+                    injection_capture = prop
+                        .value
+                        .as_ref()
+                        .map(|s| InjectionLanguageMarker::Name(s.as_ref().into()));
+                }
+
+                // By default, injections do not include the *children* of an
+                // `injection.content` node - only the ranges that belong to the
+                // node itself. This can be changed using a `#set!` predicate that
+                // sets the `injection.include-children` key.
+                "injection.include-children" => included_children = IncludedChildren::All,
+
+                // Some queries might only exclude named children but include unnamed
+                // children in their `injection.content` node. This can be enabled using
+                // a `#set!` predicate that sets the `injection.include-unnamed-children` key.
+                "injection.include-unnamed-children" => {
+                    included_children = IncludedChildren::Unnamed
+                }
+                _ => {}
+            }
+        }
+
+        (injection_capture, content_node, included_children)
+    }
+    pub fn load_query(
+        &self,
+        language: &str,
+        filename: &str,
+        read_query_text: impl FnMut(&str, &str) -> String,
+    ) -> Result<Option<Query>, QueryError> {
+        let query_text = read_query(language, filename, read_query_text);
+        if query_text.is_empty() {
+            return Ok(None);
+        }
+        Query::new(&self.language, &query_text).map(Some)
+    }
+}
+
+/// reads a query by invoking `read_query_text`, handeles any `inherits` directives
+pub fn read_query(
+    language: &str,
+    filename: &str,
+    mut read_query_text: impl FnMut(&str, &str) -> String,
+) -> String {
+    fn read_query_impl(
+        language: &str,
+        filename: &str,
+        read_query_text: &mut impl FnMut(&str, &str) -> String,
+    ) -> String {
+        static INHERITS_REGEX: Lazy<Regex> =
+            Lazy::new(|| Regex::new(r";+\s*inherits\s*:?\s*([a-z_,()-]+)\s*").unwrap());
+
+        let query = read_query_text(language, filename);
+
+        // replaces all "; inherits <language>(,<language>)*" with the queries of the given language(s)
+        INHERITS_REGEX
+            .replace_all(&query, |captures: &regex::Captures| {
+                captures[1]
+                    .split(',')
+                    .map(|language| {
+                        format!(
+                            "\n{}\n",
+                            read_query_impl(language, filename, &mut *read_query_text)
+                        )
+                    })
+                    .collect::<String>()
+            })
+            .to_string()
+    }
+    read_query_impl(language, filename, &mut read_query_text)
+}

helix-syntax/src/highlighter.rs

@@ -0,0 +1,439 @@
+use std::borrow::Cow;
+use std::cell::RefCell;
+use std::sync::atomic::{self, AtomicUsize};
+use std::{fmt, iter, mem, ops};
+
+use ropey::RopeSlice;
+use tree_sitter::{QueryCaptures, QueryCursor, Tree};
+
+use crate::ropey::RopeProvider;
+use crate::{
+    byte_range_to_str, Error, HighlightConfiguration, Syntax, PARSER, TREE_SITTER_MATCH_LIMIT,
+};
+
+const CANCELLATION_CHECK_INTERVAL: usize = 100;
+
+/// Indicates which highlight should be applied to a region of source code.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub struct Highlight(pub usize);
+
+/// Represents a single step in rendering a syntax-highlighted document.
+#[derive(Copy, Clone, Debug)]
+pub enum HighlightEvent {
+    Source { start: usize, end: usize },
+    HighlightStart(Highlight),
+    HighlightEnd,
+}
+
+#[derive(Debug)]
+struct LocalDef<'a> {
+    name: Cow<'a, str>,
+    value_range: ops::Range<usize>,
+    highlight: Option<Highlight>,
+}
+
+#[derive(Debug)]
+struct LocalScope<'a> {
+    inherits: bool,
+    range: ops::Range<usize>,
+    local_defs: Vec<LocalDef<'a>>,
+}
+
+#[derive(Debug)]
+struct HighlightIter<'a> {
+    source: RopeSlice<'a>,
+    byte_offset: usize,
+    cancellation_flag: Option<&'a AtomicUsize>,
+    layers: Vec<HighlightIterLayer<'a>>,
+    iter_count: usize,
+    next_event: Option<HighlightEvent>,
+    last_highlight_range: Option<(usize, usize, u32)>,
+}
+
+struct HighlightIterLayer<'a> {
+    _tree: Option<Tree>,
+    cursor: QueryCursor,
+    captures: RefCell<iter::Peekable<QueryCaptures<'a, 'a, RopeProvider<'a>, &'a [u8]>>>,
+    config: &'a HighlightConfiguration,
+    highlight_end_stack: Vec<usize>,
+    scope_stack: Vec<LocalScope<'a>>,
+    depth: u32,
+}
+
+impl<'a> fmt::Debug for HighlightIterLayer<'a> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("HighlightIterLayer").finish()
+    }
+}
+
+impl<'a> HighlightIterLayer<'a> {
+    // First, sort scope boundaries by their byte offset in the document. At a
+    // given position, emit scope endings before scope beginnings. Finally, emit
+    // scope boundaries from deeper layers first.
+    fn sort_key(&self) -> Option<(usize, bool, isize)> {
+        let depth = -(self.depth as isize);
+        let next_start = self
+            .captures
+            .borrow_mut()
+            .peek()
+            .map(|(m, i)| m.captures[*i].node.start_byte());
+        let next_end = self.highlight_end_stack.last().cloned();
+        match (next_start, next_end) {
+            (Some(start), Some(end)) => {
+                if start < end {
+                    Some((start, true, depth))
+                } else {
+                    Some((end, false, depth))
+                }
+            }
+            (Some(i), None) => Some((i, true, depth)),
+            (None, Some(j)) => Some((j, false, depth)),
+            _ => None,
+        }
+    }
+}
+
+impl<'a> HighlightIter<'a> {
+    fn emit_event(
+        &mut self,
+        offset: usize,
+        event: Option<HighlightEvent>,
+    ) -> Option<Result<HighlightEvent, Error>> {
+        let result;
+        if self.byte_offset < offset {
+            result = Some(Ok(HighlightEvent::Source {
+                start: self.byte_offset,
+                end: offset,
+            }));
+            self.byte_offset = offset;
+            self.next_event = event;
+        } else {
+            result = event.map(Ok);
+        }
+        self.sort_layers();
+        result
+    }
+
+    fn sort_layers(&mut self) {
+        while !self.layers.is_empty() {
+            if let Some(sort_key) = self.layers[0].sort_key() {
+                let mut i = 0;
+                while i + 1 < self.layers.len() {
+                    if let Some(next_offset) = self.layers[i + 1].sort_key() {
+                        if next_offset < sort_key {
+                            i += 1;
+                            continue;
+                        }
+                    } else {
+                        let layer = self.layers.remove(i + 1);
+                        PARSER.with(|ts_parser| {
+                            let highlighter = &mut ts_parser.borrow_mut();
+                            highlighter.cursors.push(layer.cursor);
+                        });
+                    }
+                    break;
+                }
+                if i > 0 {
+                    self.layers[0..(i + 1)].rotate_left(1);
+                }
+                break;
+            } else {
+                let layer = self.layers.remove(0);
+                PARSER.with(|ts_parser| {
+                    let highlighter = &mut ts_parser.borrow_mut();
+                    highlighter.cursors.push(layer.cursor);
+                });
+            }
+        }
+    }
+}
+
+impl<'a> Iterator for HighlightIter<'a> {
+    type Item = Result<HighlightEvent, Error>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        'main: loop {
+            // If we've already determined the next highlight boundary, just return it.
+            if let Some(e) = self.next_event.take() {
+                return Some(Ok(e));
+            }
+
+            // Periodically check for cancellation, returning `Cancelled` error if the
+            // cancellation flag was flipped.
+            if let Some(cancellation_flag) = self.cancellation_flag {
+                self.iter_count += 1;
+                if self.iter_count >= CANCELLATION_CHECK_INTERVAL {
+                    self.iter_count = 0;
+                    if cancellation_flag.load(atomic::Ordering::Relaxed) != 0 {
+                        return Some(Err(Error::Cancelled));
+                    }
+                }
+            }
+
+            // If none of the layers have any more highlight boundaries, terminate.
+            if self.layers.is_empty() {
+                let len = self.source.len_bytes();
+                return if self.byte_offset < len {
+                    let result = Some(Ok(HighlightEvent::Source {
+                        start: self.byte_offset,
+                        end: len,
+                    }));
+                    self.byte_offset = len;
+                    result
+                } else {
+                    None
+                };
+            }
+
+            // Get the next capture from whichever layer has the earliest highlight boundary.
+            let range;
+            let layer = &mut self.layers[0];
+            let captures = layer.captures.get_mut();
+            if let Some((next_match, capture_index)) = captures.peek() {
+                let next_capture = next_match.captures[*capture_index];
+                range = next_capture.node.byte_range();
+
+                // If any previous highlight ends before this node starts, then before
+                // processing this capture, emit the source code up until the end of the
+                // previous highlight, and an end event for that highlight.
+                if let Some(end_byte) = layer.highlight_end_stack.last().cloned() {
+                    if end_byte <= range.start {
+                        layer.highlight_end_stack.pop();
+                        return self.emit_event(end_byte, Some(HighlightEvent::HighlightEnd));
+                    }
+                }
+            }
+            // If there are no more captures, then emit any remaining highlight end events.
+            // And if there are none of those, then just advance to the end of the document.
+            else if let Some(end_byte) = layer.highlight_end_stack.last().cloned() {
+                layer.highlight_end_stack.pop();
+                return self.emit_event(end_byte, Some(HighlightEvent::HighlightEnd));
+            } else {
+                return self.emit_event(self.source.len_bytes(), None);
+            };
+
+            let (mut match_, capture_index) = captures.next().unwrap();
+            let mut capture = match_.captures[capture_index];
+
+            // Remove from the local scope stack any local scopes that have already ended.
+            while range.start > layer.scope_stack.last().unwrap().range.end {
+                layer.scope_stack.pop();
+            }
+
+            // If this capture is for tracking local variables, then process the
+            // local variable info.
+            let mut reference_highlight = None;
+            let mut definition_highlight = None;
+            while match_.pattern_index < layer.config.highlights_pattern_index {
+                // If the node represents a local scope, push a new local scope onto
+                // the scope stack.
+                if Some(capture.index) == layer.config.local_scope_capture_index {
+                    definition_highlight = None;
+                    let mut scope = LocalScope {
+                        inherits: true,
+                        range: range.clone(),
+                        local_defs: Vec::new(),
+                    };
+                    for prop in layer.config.query.property_settings(match_.pattern_index) {
+                        if let "local.scope-inherits" = prop.key.as_ref() {
+                            scope.inherits =
+                                prop.value.as_ref().map_or(true, |r| r.as_ref() == "true");
+                        }
+                    }
+                    layer.scope_stack.push(scope);
+                }
+                // If the node represents a definition, add a new definition to the
+                // local scope at the top of the scope stack.
+                else if Some(capture.index) == layer.config.local_def_capture_index {
+                    reference_highlight = None;
+                    let scope = layer.scope_stack.last_mut().unwrap();
+
+                    let mut value_range = 0..0;
+                    for capture in match_.captures {
+                        if Some(capture.index) == layer.config.local_def_value_capture_index {
+                            value_range = capture.node.byte_range();
+                        }
+                    }
+
+                    let name = byte_range_to_str(range.clone(), self.source);
+                    scope.local_defs.push(LocalDef {
+                        name,
+                        value_range,
+                        highlight: None,
+                    });
+                    definition_highlight = scope.local_defs.last_mut().map(|s| &mut s.highlight);
+                }
+                // If the node represents a reference, then try to find the corresponding
+                // definition in the scope stack.
+                else if Some(capture.index) == layer.config.local_ref_capture_index
+                    && definition_highlight.is_none()
+                {
+                    definition_highlight = None;
+                    let name = byte_range_to_str(range.clone(), self.source);
+                    for scope in layer.scope_stack.iter().rev() {
+                        if let Some(highlight) = scope.local_defs.iter().rev().find_map(|def| {
+                            if def.name == name && range.start >= def.value_range.end {
+                                Some(def.highlight)
+                            } else {
+                                None
+                            }
+                        }) {
+                            reference_highlight = highlight;
+                            break;
+                        }
+                        if !scope.inherits {
+                            break;
+                        }
+                    }
+                }
+
+                // Continue processing any additional matches for the same node.
+                if let Some((next_match, next_capture_index)) = captures.peek() {
+                    let next_capture = next_match.captures[*next_capture_index];
+                    if next_capture.node == capture.node {
+                        capture = next_capture;
+                        match_ = captures.next().unwrap().0;
+                        continue;
+                    }
+                }
+
+                self.sort_layers();
+                continue 'main;
+            }
+
+            // Otherwise, this capture must represent a highlight.
+            // If this exact range has already been highlighted by an earlier pattern, or by
+            // a different layer, then skip over this one.
+            if let Some((last_start, last_end, last_depth)) = self.last_highlight_range {
+                if range.start == last_start && range.end == last_end && layer.depth < last_depth {
+                    self.sort_layers();
+                    continue 'main;
+                }
+            }
+
+            // If the current node was found to be a local variable, then skip over any
+            // highlighting patterns that are disabled for local variables.
+            if definition_highlight.is_some() || reference_highlight.is_some() {
+                while layer.config.non_local_variable_patterns[match_.pattern_index] {
+                    match_.remove();
+                    if let Some((next_match, next_capture_index)) = captures.peek() {
+                        let next_capture = next_match.captures[*next_capture_index];
+                        if next_capture.node == capture.node {
+                            capture = next_capture;
+                            match_ = captures.next().unwrap().0;
+                            continue;
+                        }
+                    }
+
+                    self.sort_layers();
+                    continue 'main;
+                }
+            }
+
+            // Once a highlighting pattern is found for the current node, skip over
+            // any later highlighting patterns that also match this node. Captures
+            // for a given node are ordered by pattern index, so these subsequent
+            // captures are guaranteed to be for highlighting, not injections or
+            // local variables.
+            while let Some((next_match, next_capture_index)) = captures.peek() {
+                let next_capture = next_match.captures[*next_capture_index];
+                if next_capture.node == capture.node {
+                    captures.next();
+                } else {
+                    break;
+                }
+            }
+
+            let current_highlight = layer.config.highlight_indices.load()[capture.index as usize];
+
+            // If this node represents a local definition, then store the current
+            // highlight value on the local scope entry representing this node.
+            if let Some(definition_highlight) = definition_highlight {
+                *definition_highlight = current_highlight;
+            }
+
+            // Emit a scope start event and push the node's end position to the stack.
+            if let Some(highlight) = reference_highlight.or(current_highlight) {
+                self.last_highlight_range = Some((range.start, range.end, layer.depth));
+                layer.highlight_end_stack.push(range.end);
+                return self
+                    .emit_event(range.start, Some(HighlightEvent::HighlightStart(highlight)));
+            }
+
+            self.sort_layers();
+        }
+    }
+}
+
+impl Syntax {
+    /// Iterate over the highlighted regions for a given slice of source code.
+    pub fn highlight_iter<'a>(
+        &'a self,
+        source: RopeSlice<'a>,
+        range: Option<std::ops::Range<usize>>,
+        cancellation_flag: Option<&'a AtomicUsize>,
+    ) -> impl Iterator<Item = Result<HighlightEvent, Error>> + 'a {
+        let mut layers = self
+            .layers
+            .iter()
+            .filter_map(|(_, layer)| {
+                // TODO: if range doesn't overlap layer range, skip it
+
+                // Reuse a cursor from the pool if available.
+                let mut cursor = PARSER.with(|ts_parser| {
+                    let highlighter = &mut ts_parser.borrow_mut();
+                    highlighter.cursors.pop().unwrap_or_else(QueryCursor::new)
+                });
+
+                // The `captures` iterator borrows the `Tree` and the `QueryCursor`, which
+                // prevents them from being moved. But both of these values are really just
+                // pointers, so it's actually ok to move them.
+                let cursor_ref =
+                    unsafe { mem::transmute::<_, &'static mut QueryCursor>(&mut cursor) };
+
+                // if reusing cursors & no range this resets to whole range
+                cursor_ref.set_byte_range(range.clone().unwrap_or(0..usize::MAX));
+                cursor_ref.set_match_limit(TREE_SITTER_MATCH_LIMIT);
+
+                let mut captures = cursor_ref
+                    .captures(
+                        &layer.config.query,
+                        layer.tree().root_node(),
+                        RopeProvider(source),
+                    )
+                    .peekable();
+
+                // If there's no captures, skip the layer
+                captures.peek()?;
+
+                Some(HighlightIterLayer {
+                    highlight_end_stack: Vec::new(),
+                    scope_stack: vec![LocalScope {
+                        inherits: false,
+                        range: 0..usize::MAX,
+                        local_defs: Vec::new(),
+                    }],
+                    cursor,
+                    _tree: None,
+                    captures: RefCell::new(captures),
+                    config: layer.config.as_ref(), // TODO: just reuse `layer`
+                    depth: layer.depth,            // TODO: just reuse `layer`
+                })
+            })
+            .collect::<Vec<_>>();
+
+        layers.sort_unstable_by_key(|layer| layer.sort_key());
+
+        let mut result = HighlightIter {
+            source,
+            byte_offset: range.map_or(0, |r| r.start),
+            cancellation_flag,
+            iter_count: 0,
+            layers,
+            next_event: None,
+            last_highlight_range: None,
+        };
+        result.sort_layers();
+        result
+    }
+}

helix-syntax/src/lib.rs

@@ -0,0 +1,342 @@
+use ::ropey::RopeSlice;
+use slotmap::{DefaultKey as LayerId, HopSlotMap};
+use tree_sitter::{Node, Parser, Point, Query, QueryCursor, Range, Tree};
+
+use std::borrow::Cow;
+use std::cell::RefCell;
+use std::hash::{Hash, Hasher};
+use std::path::Path;
+use std::str;
+use std::sync::Arc;
+
+use crate::parse::LayerUpdateFlags;
+
+pub use crate::config::{read_query, HighlightConfiguration};
+pub use crate::ropey::RopeProvider;
+pub use merge::merge;
+pub use pretty_print::pretty_print_tree;
+pub use tree_cursor::TreeCursor;
+
+mod config;
+pub mod highlighter;
+mod merge;
+mod parse;
+mod pretty_print;
+mod ropey;
+mod tree_cursor;
+
+#[derive(Debug)]
+pub struct Syntax {
+    layers: HopSlotMap<LayerId, LanguageLayer>,
+    root: LayerId,
+}
+
+impl Syntax {
+    pub fn new(
+        source: RopeSlice,
+        config: Arc<HighlightConfiguration>,
+        injection_callback: impl Fn(&InjectionLanguageMarker) -> Option<Arc<HighlightConfiguration>>,
+    ) -> Option<Self> {
+        let root_layer = LanguageLayer {
+            tree: None,
+            config,
+            depth: 0,
+            flags: LayerUpdateFlags::empty(),
+            ranges: vec![Range {
+                start_byte: 0,
+                end_byte: usize::MAX,
+                start_point: Point::new(0, 0),
+                end_point: Point::new(usize::MAX, usize::MAX),
+            }],
+            parent: None,
+        };
+
+        // track scope_descriptor: a Vec of scopes for item in tree
+
+        let mut layers = HopSlotMap::default();
+        let root = layers.insert(root_layer);
+
+        let mut syntax = Self { root, layers };
+
+        let res = syntax.update(source, Vec::new(), injection_callback);
+
+        if res.is_err() {
+            log::error!("TS parser failed, disabling TS for the current buffer: {res:?}");
+            return None;
+        }
+        Some(syntax)
+    }
+
+    pub fn tree(&self) -> &Tree {
+        self.layers[self.root].tree()
+    }
+
+    pub fn tree_for_byte_range(&self, start: usize, end: usize) -> &Tree {
+        let mut container_id = self.root;
+
+        for (layer_id, layer) in self.layers.iter() {
+            if layer.depth > self.layers[container_id].depth
+                && layer.contains_byte_range(start, end)
+            {
+                container_id = layer_id;
+            }
+        }
+
+        self.layers[container_id].tree()
+    }
+
+    pub fn named_descendant_for_byte_range(&self, start: usize, end: usize) -> Option<Node<'_>> {
+        self.tree_for_byte_range(start, end)
+            .root_node()
+            .named_descendant_for_byte_range(start, end)
+    }
+
+    pub fn descendant_for_byte_range(&self, start: usize, end: usize) -> Option<Node<'_>> {
+        self.tree_for_byte_range(start, end)
+            .root_node()
+            .descendant_for_byte_range(start, end)
+    }
+
+    pub fn walk(&self) -> TreeCursor<'_> {
+        TreeCursor::new(&self.layers, self.root)
+    }
+}
+
+#[derive(Debug)]
+pub struct LanguageLayer {
+    // mode
+    // grammar
+    pub config: Arc<HighlightConfiguration>,
+    pub(crate) tree: Option<Tree>,
+    pub ranges: Vec<Range>,
+    pub depth: u32,
+    flags: LayerUpdateFlags,
+    parent: Option<LayerId>,
+}
+
+/// This PartialEq implementation only checks if that
+/// two layers are theoretically identical (meaning they highlight the same text range with the same language).
+/// It does not check whether the layers have the same internal treesitter
+/// state.
+impl PartialEq for LanguageLayer {
+    fn eq(&self, other: &Self) -> bool {
+        self.depth == other.depth
+            && self.config.language == other.config.language
+            && self.ranges == other.ranges
+    }
+}
+
+/// Hash implementation belongs to PartialEq implementation above.
+/// See its documentation for details.
+impl Hash for LanguageLayer {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.depth.hash(state);
+        self.config.language.hash(state);
+        self.ranges.hash(state);
+    }
+}
+
+impl LanguageLayer {
+    pub fn tree(&self) -> &Tree {
+        // TODO: no unwrap
+        self.tree.as_ref().unwrap()
+    }
+
+    /// Whether the layer contains the given byte range.
+    ///
+    /// If the layer has multiple ranges (i.e. combined injections), the
+    /// given range is considered contained if it is within the start and
+    /// end bytes of the first and last ranges **and** if the given range
+    /// starts or ends within any of the layer's ranges.
+    fn contains_byte_range(&self, start: usize, end: usize) -> bool {
+        let layer_start = self
+            .ranges
+            .first()
+            .expect("ranges should not be empty")
+            .start_byte;
+        let layer_end = self
+            .ranges
+            .last()
+            .expect("ranges should not be empty")
+            .end_byte;
+
+        layer_start <= start
+            && layer_end >= end
+            && self.ranges.iter().any(|range| {
+                let byte_range = range.start_byte..range.end_byte;
+                byte_range.contains(&start) || byte_range.contains(&end)
+            })
+    }
+}
+
+#[derive(Debug, Clone)]
+pub enum InjectionLanguageMarker<'a> {
+    Name(Cow<'a, str>),
+    Filename(Cow<'a, Path>),
+    Shebang(String),
+}
+
+const SHEBANG: &str = r"#!\s*(?:\S*[/\\](?:env\s+(?:\-\S+\s+)*)?)?([^\s\.\d]+)";
+
+#[derive(Debug)]
+pub enum CapturedNode<'a> {
+    Single(Node<'a>),
+    /// Guaranteed to be not empty
+    Grouped(Vec<Node<'a>>),
+}
+
+impl<'a> CapturedNode<'a> {
+    pub fn start_byte(&self) -> usize {
+        match self {
+            Self::Single(n) => n.start_byte(),
+            Self::Grouped(ns) => ns[0].start_byte(),
+        }
+    }
+
+    pub fn end_byte(&self) -> usize {
+        match self {
+            Self::Single(n) => n.end_byte(),
+            Self::Grouped(ns) => ns.last().unwrap().end_byte(),
+        }
+    }
+
+    pub fn byte_range(&self) -> std::ops::Range<usize> {
+        self.start_byte()..self.end_byte()
+    }
+}
+
+/// The maximum number of in-progress matches a TS cursor can consider at once.
+/// This is set to a constant in order to avoid performance problems for medium to large files. Set with `set_match_limit`.
+/// Using such a limit means that we lose valid captures, so there is fundamentally a tradeoff here.
+///
+///
+/// Old tree sitter versions used a limit of 32 by default until this limit was removed in version `0.19.5` (must now be set manually).
+/// However, this causes performance issues for medium to large files.
+/// In helix, this problem caused treesitter motions to take multiple seconds to complete in medium-sized rust files (3k loc).
+///
+///
+/// Neovim also encountered this problem and reintroduced this limit after it was removed upstream
+/// (see <https://github.com/neovim/neovim/issues/14897> and <https://github.com/neovim/neovim/pull/14915>).
+/// The number used here is fundamentally a tradeoff between breaking some obscure edge cases and performance.
+///
+///
+/// Neovim chose 64 for this value somewhat arbitrarily (<https://github.com/neovim/neovim/pull/18397>).
+/// 64 is too low for some languages though. In particular, it breaks some highlighting for record fields in Erlang record definitions.
+/// This number can be increased if new syntax highlight breakages are found, as long as the performance penalty is not too high.
+const TREE_SITTER_MATCH_LIMIT: u32 = 256;
+
+#[derive(Debug)]
+pub struct TextObjectQuery {
+    pub query: Query,
+}
+
+impl TextObjectQuery {
+    /// Run the query on the given node and return sub nodes which match given
+    /// capture ("function.inside", "class.around", etc).
+    ///
+    /// Captures may contain multiple nodes by using quantifiers (+, *, etc),
+    /// and support for this is partial and could use improvement.
+    ///
+    /// ```query
+    /// (comment)+ @capture
+    ///
+    /// ; OR
+    /// (
+    ///   (comment)*
+    ///   .
+    ///   (function)
+    /// ) @capture
+    /// ```
+    pub fn capture_nodes<'a>(
+        &'a self,
+        capture_name: &str,
+        node: Node<'a>,
+        slice: RopeSlice<'a>,
+        cursor: &'a mut QueryCursor,
+    ) -> Option<impl Iterator<Item = CapturedNode<'a>>> {
+        self.capture_nodes_any(&[capture_name], node, slice, cursor)
+    }
+
+    /// Find the first capture that exists out of all given `capture_names`
+    /// and return sub nodes that match this capture.
+    pub fn capture_nodes_any<'a>(
+        &'a self,
+        capture_names: &[&str],
+        node: Node<'a>,
+        slice: RopeSlice<'a>,
+        cursor: &'a mut QueryCursor,
+    ) -> Option<impl Iterator<Item = CapturedNode<'a>>> {
+        let capture_idx = capture_names
+            .iter()
+            .find_map(|cap| self.query.capture_index_for_name(cap))?;
+
+        cursor.set_match_limit(TREE_SITTER_MATCH_LIMIT);
+
+        let nodes = cursor
+            .captures(&self.query, node, RopeProvider(slice))
+            .filter_map(move |(mat, _)| {
+                let nodes: Vec<_> = mat
+                    .captures
+                    .iter()
+                    .filter_map(|cap| (cap.index == capture_idx).then_some(cap.node))
+                    .collect();
+
+                if nodes.len() > 1 {
+                    Some(CapturedNode::Grouped(nodes))
+                } else {
+                    nodes.into_iter().map(CapturedNode::Single).next()
+                }
+            });
+
+        Some(nodes)
+    }
+}
+
+/// Represents the reason why syntax highlighting failed.
+#[derive(Debug, PartialEq, Eq)]
+pub enum Error {
+    Cancelled,
+    InvalidLanguage,
+    InvalidRanges,
+    Unknown,
+}
+
+#[derive(Clone)]
+enum IncludedChildren {
+    None,
+    All,
+    Unnamed,
+}
+
+impl Default for IncludedChildren {
+    fn default() -> Self {
+        Self::None
+    }
+}
+
+fn byte_range_to_str(range: std::ops::Range<usize>, source: RopeSlice) -> Cow<str> {
+    Cow::from(source.byte_slice(range))
+}
+
+struct TsParser {
+    parser: tree_sitter::Parser,
+    pub cursors: Vec<QueryCursor>,
+}
+
+// could also just use a pool, or a single instance?
+thread_local! {
+    static PARSER: RefCell<TsParser> = RefCell::new(TsParser {
+        parser: Parser::new(),
+        cursors: Vec::new(),
+    })
+}
+
+pub fn with_cursor<T>(f: impl FnOnce(&mut QueryCursor) -> T) -> T {
+    PARSER.with(|parser| {
+        let mut parser = parser.borrow_mut();
+        let mut cursor = parser.cursors.pop().unwrap_or_else(QueryCursor::new);
+        let res = f(&mut cursor);
+        parser.cursors.push(cursor);
+        res
+    })
+}

helix-syntax/src/merge.rs

@@ -0,0 +1,135 @@
+use crate::highlighter::{Highlight, HighlightEvent};
+
+pub struct Merge<I> {
+    iter: I,
+    spans: Box<dyn Iterator<Item = (usize, std::ops::Range<usize>)>>,
+
+    next_event: Option<HighlightEvent>,
+    next_span: Option<(usize, std::ops::Range<usize>)>,
+
+    queue: Vec<HighlightEvent>,
+}
+
+/// Merge a list of spans into the highlight event stream.
+pub fn merge<I: Iterator<Item = HighlightEvent>>(
+    iter: I,
+    spans: Vec<(usize, std::ops::Range<usize>)>,
+) -> Merge<I> {
+    let spans = Box::new(spans.into_iter());
+    let mut merge = Merge {
+        iter,
+        spans,
+        next_event: None,
+        next_span: None,
+        queue: Vec::new(),
+    };
+    merge.next_event = merge.iter.next();
+    merge.next_span = merge.spans.next();
+    merge
+}
+
+impl<I: Iterator<Item = HighlightEvent>> Iterator for Merge<I> {
+    type Item = HighlightEvent;
+    fn next(&mut self) -> Option<Self::Item> {
+        use HighlightEvent::*;
+        if let Some(event) = self.queue.pop() {
+            return Some(event);
+        }
+
+        loop {
+            match (self.next_event, &self.next_span) {
+                // this happens when range is partially or fully offscreen
+                (Some(Source { start, .. }), Some((span, range))) if start > range.start => {
+                    if start > range.end {
+                        self.next_span = self.spans.next();
+                    } else {
+                        self.next_span = Some((*span, start..range.end));
+                    };
+                }
+                _ => break,
+            }
+        }
+
+        match (self.next_event, &self.next_span) {
+            (Some(HighlightStart(i)), _) => {
+                self.next_event = self.iter.next();
+                Some(HighlightStart(i))
+            }
+            (Some(HighlightEnd), _) => {
+                self.next_event = self.iter.next();
+                Some(HighlightEnd)
+            }
+            (Some(Source { start, end }), Some((_, range))) if start < range.start => {
+                let intersect = range.start.min(end);
+                let event = Source {
+                    start,
+                    end: intersect,
+                };
+
+                if end == intersect {
+                    // the event is complete
+                    self.next_event = self.iter.next();
+                } else {
+                    // subslice the event
+                    self.next_event = Some(Source {
+                        start: intersect,
+                        end,
+                    });
+                };
+
+                Some(event)
+            }
+            (Some(Source { start, end }), Some((span, range))) if start == range.start => {
+                let intersect = range.end.min(end);
+                let event = HighlightStart(Highlight(*span));
+
+                // enqueue in reverse order
+                self.queue.push(HighlightEnd);
+                self.queue.push(Source {
+                    start,
+                    end: intersect,
+                });
+
+                if end == intersect {
+                    // the event is complete
+                    self.next_event = self.iter.next();
+                } else {
+                    // subslice the event
+                    self.next_event = Some(Source {
+                        start: intersect,
+                        end,
+                    });
+                };
+
+                if intersect == range.end {
+                    self.next_span = self.spans.next();
+                } else {
+                    self.next_span = Some((*span, intersect..range.end));
+                }
+
+                Some(event)
+            }
+            (Some(event), None) => {
+                self.next_event = self.iter.next();
+                Some(event)
+            }
+            // Can happen if cursor at EOF and/or diagnostic reaches past the end.
+            // We need to actually emit events for the cursor-at-EOF situation,
+            // even though the range is past the end of the text.  This needs to be
+            // handled appropriately by the drawing code by not assuming that
+            // all `Source` events point to valid indices in the rope.
+            (None, Some((span, range))) => {
+                let event = HighlightStart(Highlight(*span));
+                self.queue.push(HighlightEnd);
+                self.queue.push(Source {
+                    start: range.start,
+                    end: range.end,
+                });
+                self.next_span = self.spans.next();
+                Some(event)
+            }
+            (None, None) => None,
+            e => unreachable!("{:?}", e),
+        }
+    }
+}

helix-syntax/src/parse.rs

@@ -0,0 +1,429 @@
+use std::collections::VecDeque;
+use std::mem::replace;
+use std::sync::Arc;
+
+use ahash::RandomState;
+use bitflags::bitflags;
+use hashbrown::raw::RawTable;
+use ropey::RopeSlice;
+use tree_sitter::{Node, Parser, Point, QueryCursor, Range};
+
+use crate::ropey::RopeProvider;
+use crate::{
+    Error, HighlightConfiguration, IncludedChildren, InjectionLanguageMarker, LanguageLayer,
+    Syntax, PARSER, TREE_SITTER_MATCH_LIMIT,
+};
+
+bitflags! {
+    /// Flags that track the status of a layer
+    /// in the `Sytaxn::update` function
+    #[derive(Debug)]
+    pub(crate) struct LayerUpdateFlags : u32{
+        const MODIFIED = 0b001;
+        const MOVED = 0b010;
+        const TOUCHED = 0b100;
+    }
+}
+
+impl Syntax {
+    pub fn update(
+        &mut self,
+        source: RopeSlice,
+        edits: Vec<tree_sitter::InputEdit>,
+        injection_callback: impl Fn(&InjectionLanguageMarker) -> Option<Arc<HighlightConfiguration>>,
+    ) -> Result<(), Error> {
+        let mut queue = VecDeque::new();
+        queue.push_back(self.root);
+
+        // This table allows inverse indexing of `layers`.
+        // That is by hashing a `Layer` you can find
+        // the `LayerId` of an existing equivalent `Layer` in `layers`.
+        //
+        // It is used to determine if a new layer exists for an injection
+        // or if an existing layer needs to be updated.
+        let mut layers_table = RawTable::with_capacity(self.layers.len());
+        let layers_hasher = RandomState::new();
+        // Use the edits to update all layers markers
+        fn point_add(a: Point, b: Point) -> Point {
+            if b.row > 0 {
+                Point::new(a.row.saturating_add(b.row), b.column)
+            } else {
+                Point::new(0, a.column.saturating_add(b.column))
+            }
+        }
+        fn point_sub(a: Point, b: Point) -> Point {
+            if a.row > b.row {
+                Point::new(a.row.saturating_sub(b.row), a.column)
+            } else {
+                Point::new(0, a.column.saturating_sub(b.column))
+            }
+        }
+
+        for (layer_id, layer) in self.layers.iter_mut() {
+            // The root layer always covers the whole range (0..usize::MAX)
+            if layer.depth == 0 {
+                layer.flags = LayerUpdateFlags::MODIFIED;
+                continue;
+            }
+
+            if !edits.is_empty() {
+                for range in &mut layer.ranges {
+                    // Roughly based on https://github.com/tree-sitter/tree-sitter/blob/ddeaa0c7f534268b35b4f6cb39b52df082754413/lib/src/subtree.c#L691-L720
+                    for edit in edits.iter().rev() {
+                        let is_pure_insertion = edit.old_end_byte == edit.start_byte;
+
+                        // if edit is after range, skip
+                        if edit.start_byte > range.end_byte {
+                            // TODO: || (is_noop && edit.start_byte == range.end_byte)
+                            continue;
+                        }
+
+                        // if edit is before range, shift entire range by len
+                        if edit.old_end_byte < range.start_byte {
+                            range.start_byte =
+                                edit.new_end_byte + (range.start_byte - edit.old_end_byte);
+                            range.start_point = point_add(
+                                edit.new_end_position,
+                                point_sub(range.start_point, edit.old_end_position),
+                            );
+
+                            range.end_byte = edit
+                                .new_end_byte
+                                .saturating_add(range.end_byte - edit.old_end_byte);
+                            range.end_point = point_add(
+                                edit.new_end_position,
+                                point_sub(range.end_point, edit.old_end_position),
+                            );
+
+                            layer.flags |= LayerUpdateFlags::MOVED;
+                        }
+                        // if the edit starts in the space before and extends into the range
+                        else if edit.start_byte < range.start_byte {
+                            range.start_byte = edit.new_end_byte;
+                            range.start_point = edit.new_end_position;
+
+                            range.end_byte = range
+                                .end_byte
+                                .saturating_sub(edit.old_end_byte)
+                                .saturating_add(edit.new_end_byte);
+                            range.end_point = point_add(
+                                edit.new_end_position,
+                                point_sub(range.end_point, edit.old_end_position),
+                            );
+                            layer.flags = LayerUpdateFlags::MODIFIED;
+                        }
+                        // If the edit is an insertion at the start of the tree, shift
+                        else if edit.start_byte == range.start_byte && is_pure_insertion {
+                            range.start_byte = edit.new_end_byte;
+                            range.start_point = edit.new_end_position;
+                            layer.flags |= LayerUpdateFlags::MOVED;
+                        } else {
+                            range.end_byte = range
+                                .end_byte
+                                .saturating_sub(edit.old_end_byte)
+                                .saturating_add(edit.new_end_byte);
+                            range.end_point = point_add(
+                                edit.new_end_position,
+                                point_sub(range.end_point, edit.old_end_position),
+                            );
+                            layer.flags = LayerUpdateFlags::MODIFIED;
+                        }
+                    }
+                }
+            }
+
+            let hash = layers_hasher.hash_one(layer);
+            // Safety: insert_no_grow is unsafe because it assumes that the table
+            // has enough capacity to hold additional elements.
+            // This is always the case as we reserved enough capacity above.
+            unsafe { layers_table.insert_no_grow(hash, layer_id) };
+        }
+
+        PARSER.with(|ts_parser| {
+            let ts_parser = &mut ts_parser.borrow_mut();
+            ts_parser.parser.set_timeout_micros(1000 * 500); // half a second is pretty generours
+            let mut cursor = ts_parser.cursors.pop().unwrap_or_else(QueryCursor::new);
+            // TODO: might need to set cursor range
+            cursor.set_byte_range(0..usize::MAX);
+            cursor.set_match_limit(TREE_SITTER_MATCH_LIMIT);
+
+            let source_slice = source.slice(..);
+
+            while let Some(layer_id) = queue.pop_front() {
+                let layer = &mut self.layers[layer_id];
+
+                // Mark the layer as touched
+                layer.flags |= LayerUpdateFlags::TOUCHED;
+
+                // If a tree already exists, notify it of changes.
+                if let Some(tree) = &mut layer.tree {
+                    if layer
+                        .flags
+                        .intersects(LayerUpdateFlags::MODIFIED | LayerUpdateFlags::MOVED)
+                    {
+                        for edit in edits.iter().rev() {
+                            // Apply the edits in reverse.
+                            // If we applied them in order then edit 1 would disrupt the positioning of edit 2.
+                            tree.edit(edit);
+                        }
+                    }
+
+                    if layer.flags.contains(LayerUpdateFlags::MODIFIED) {
+                        // Re-parse the tree.
+                        layer.parse(&mut ts_parser.parser, source)?;
+                    }
+                } else {
+                    // always parse if this layer has never been parsed before
+                    layer.parse(&mut ts_parser.parser, source)?;
+                }
+
+                // Switch to an immutable borrow.
+                let layer = &self.layers[layer_id];
+
+                // Process injections.
+                let matches = cursor.matches(
+                    &layer.config.injections_query,
+                    layer.tree().root_node(),
+                    RopeProvider(source_slice),
+                );
+                let mut combined_injections = vec![
+                    (None, Vec::new(), IncludedChildren::default());
+                    layer.config.combined_injections_patterns.len()
+                ];
+                let mut injections = Vec::new();
+                let mut last_injection_end = 0;
+                for mat in matches {
+                    let (injection_capture, content_node, included_children) = layer
+                        .config
+                        .injection_for_match(&layer.config.injections_query, &mat, source_slice);
+
+                    // in case this is a combined injection save it for more processing later
+                    if let Some(combined_injection_idx) = layer
+                        .config
+                        .combined_injections_patterns
+                        .iter()
+                        .position(|&pattern| pattern == mat.pattern_index)
+                    {
+                        let entry = &mut combined_injections[combined_injection_idx];
+                        if injection_capture.is_some() {
+                            entry.0 = injection_capture;
+                        }
+                        if let Some(content_node) = content_node {
+                            if content_node.start_byte() >= last_injection_end {
+                                entry.1.push(content_node);
+                                last_injection_end = content_node.end_byte();
+                            }
+                        }
+                        entry.2 = included_children;
+                        continue;
+                    }
+
+                    // Explicitly remove this match so that none of its other captures will remain
+                    // in the stream of captures.
+                    mat.remove();
+
+                    // If a language is found with the given name, then add a new language layer
+                    // to the highlighted document.
+                    if let (Some(injection_capture), Some(content_node)) =
+                        (injection_capture, content_node)
+                    {
+                        if let Some(config) = (injection_callback)(&injection_capture) {
+                            let ranges =
+                                intersect_ranges(&layer.ranges, &[content_node], included_children);
+
+                            if !ranges.is_empty() {
+                                if content_node.start_byte() < last_injection_end {
+                                    continue;
+                                }
+                                last_injection_end = content_node.end_byte();
+                                injections.push((config, ranges));
+                            }
+                        }
+                    }
+                }
+
+                for (lang_name, content_nodes, included_children) in combined_injections {
+                    if let (Some(lang_name), false) = (lang_name, content_nodes.is_empty()) {
+                        if let Some(config) = (injection_callback)(&lang_name) {
+                            let ranges =
+                                intersect_ranges(&layer.ranges, &content_nodes, included_children);
+                            if !ranges.is_empty() {
+                                injections.push((config, ranges));
+                            }
+                        }
+                    }
+                }
+
+                let depth = layer.depth + 1;
+                // TODO: can't inline this since matches borrows self.layers
+                for (config, ranges) in injections {
+                    let parent = Some(layer_id);
+                    let new_layer = LanguageLayer {
+                        tree: None,
+                        config,
+                        depth,
+                        ranges,
+                        flags: LayerUpdateFlags::empty(),
+                        parent: None,
+                    };
+
+                    // Find an identical existing layer
+                    let layer = layers_table
+                        .get(layers_hasher.hash_one(&new_layer), |&it| {
+                            self.layers[it] == new_layer
+                        })
+                        .copied();
+
+                    // ...or insert a new one.
+                    let layer_id = layer.unwrap_or_else(|| self.layers.insert(new_layer));
+                    self.layers[layer_id].parent = parent;
+
+                    queue.push_back(layer_id);
+                }
+
+                // TODO: pre-process local scopes at this time, rather than highlight?
+                // would solve problems with locals not working across boundaries
+            }
+
+            // Return the cursor back in the pool.
+            ts_parser.cursors.push(cursor);
+
+            // Reset all `LayerUpdateFlags` and remove all untouched layers
+            self.layers.retain(|_, layer| {
+                replace(&mut layer.flags, LayerUpdateFlags::empty())
+                    .contains(LayerUpdateFlags::TOUCHED)
+            });
+
+            Ok(())
+        })
+    }
+}
+
+/// Compute the ranges that should be included when parsing an injection.
+/// This takes into account three things:
+/// * `parent_ranges` - The ranges must all fall within the *current* layer's ranges.
+/// * `nodes` - Every injection takes place within a set of nodes. The injection ranges
+///   are the ranges of those nodes.
+/// * `includes_children` - For some injections, the content nodes' children should be
+///   excluded from the nested document, so that only the content nodes' *own* content
+///   is reparsed. For other injections, the content nodes' entire ranges should be
+///   reparsed, including the ranges of their children.
+fn intersect_ranges(
+    parent_ranges: &[Range],
+    nodes: &[Node],
+    included_children: IncludedChildren,
+) -> Vec<Range> {
+    let mut cursor = nodes[0].walk();
+    let mut result = Vec::new();
+    let mut parent_range_iter = parent_ranges.iter();
+    let mut parent_range = parent_range_iter
+        .next()
+        .expect("Layers should only be constructed with non-empty ranges vectors");
+    for node in nodes.iter() {
+        let mut preceding_range = Range {
+            start_byte: 0,
+            start_point: Point::new(0, 0),
+            end_byte: node.start_byte(),
+            end_point: node.start_position(),
+        };
+        let following_range = Range {
+            start_byte: node.end_byte(),
+            start_point: node.end_position(),
+            end_byte: usize::MAX,
+            end_point: Point::new(usize::MAX, usize::MAX),
+        };
+
+        for excluded_range in node
+            .children(&mut cursor)
+            .filter_map(|child| match included_children {
+                IncludedChildren::None => Some(child.range()),
+                IncludedChildren::All => None,
+                IncludedChildren::Unnamed => {
+                    if child.is_named() {
+                        Some(child.range())
+                    } else {
+                        None
+                    }
+                }
+            })
+            .chain([following_range].iter().cloned())
+        {
+            let mut range = Range {
+                start_byte: preceding_range.end_byte,
+                start_point: preceding_range.end_point,
+                end_byte: excluded_range.start_byte,
+                end_point: excluded_range.start_point,
+            };
+            preceding_range = excluded_range;
+
+            if range.end_byte < parent_range.start_byte {
+                continue;
+            }
+
+            while parent_range.start_byte <= range.end_byte {
+                if parent_range.end_byte > range.start_byte {
+                    if range.start_byte < parent_range.start_byte {
+                        range.start_byte = parent_range.start_byte;
+                        range.start_point = parent_range.start_point;
+                    }
+
+                    if parent_range.end_byte < range.end_byte {
+                        if range.start_byte < parent_range.end_byte {
+                            result.push(Range {
+                                start_byte: range.start_byte,
+                                start_point: range.start_point,
+                                end_byte: parent_range.end_byte,
+                                end_point: parent_range.end_point,
+                            });
+                        }
+                        range.start_byte = parent_range.end_byte;
+                        range.start_point = parent_range.end_point;
+                    } else {
+                        if range.start_byte < range.end_byte {
+                            result.push(range);
+                        }
+                        break;
+                    }
+                }
+
+                if let Some(next_range) = parent_range_iter.next() {
+                    parent_range = next_range;
+                } else {
+                    return result;
+                }
+            }
+        }
+    }
+    result
+}
+
+impl LanguageLayer {
+    fn parse(&mut self, parser: &mut Parser, source: RopeSlice) -> Result<(), Error> {
+        parser
+            .set_included_ranges(&self.ranges)
+            .map_err(|_| Error::InvalidRanges)?;
+
+        parser
+            .set_language(&self.config.language)
+            .map_err(|_| Error::InvalidLanguage)?;
+
+        // unsafe { syntax.parser.set_cancellation_flag(cancellation_flag) };
+        let tree = parser
+            .parse_with(
+                &mut |byte, _| {
+                    if byte <= source.len_bytes() {
+                        let (chunk, start_byte, _, _) = source.chunk_at_byte(byte);
+                        &chunk.as_bytes()[byte - start_byte..]
+                    } else {
+                        // out of range
+                        &[]
+                    }
+                },
+                self.tree.as_ref(),
+            )
+            .ok_or(Error::Cancelled)?;
+        // unsafe { ts_parser.parser.set_cancellation_flag(None) };
+        self.tree = Some(tree);
+        Ok(())
+    }
+}

helix-syntax/src/pretty_print.rs

@@ -0,0 +1,65 @@
+use std::fmt;
+
+use tree_sitter::{Node, TreeCursor};
+
+pub fn pretty_print_tree<W: fmt::Write>(fmt: &mut W, node: Node) -> fmt::Result {
+    if node.child_count() == 0 {
+        if node_is_visible(&node) {
+            write!(fmt, "({})", node.kind())
+        } else {
+            write!(fmt, "\"{}\"", node.kind())
+        }
+    } else {
+        pretty_print_tree_impl(fmt, &mut node.walk(), 0)
+    }
+}
+
+fn pretty_print_tree_impl<W: fmt::Write>(
+    fmt: &mut W,
+    cursor: &mut TreeCursor,
+    depth: usize,
+) -> fmt::Result {
+    let node = cursor.node();
+    let visible = node_is_visible(&node);
+
+    if visible {
+        let indentation_columns = depth * 2;
+        write!(fmt, "{:indentation_columns$}", "")?;
+
+        if let Some(field_name) = cursor.field_name() {
+            write!(fmt, "{}: ", field_name)?;
+        }
+
+        write!(fmt, "({}", node.kind())?;
+    }
+
+    // Handle children.
+    if cursor.goto_first_child() {
+        loop {
+            if node_is_visible(&cursor.node()) {
+                fmt.write_char('\n')?;
+            }
+
+            pretty_print_tree_impl(fmt, cursor, depth + 1)?;
+
+            if !cursor.goto_next_sibling() {
+                break;
+            }
+        }
+
+        let moved = cursor.goto_parent();
+        // The parent of the first child must exist, and must be `node`.
+        debug_assert!(moved);
+        debug_assert!(cursor.node() == node);
+    }
+
+    if visible {
+        fmt.write_char(')')?;
+    }
+
+    Ok(())
+}
+
+fn node_is_visible(node: &Node) -> bool {
+    node.is_missing() || (node.is_named() && node.language().node_kind_is_visible(node.kind_id()))
+}

helix-syntax/src/ropey.rs

@@ -0,0 +1,29 @@
+// glue code for using TS with ropey, this should be put behind a feature flag
+// in the future (and potentially be partially removed)
+
+use ropey::RopeSlice;
+use tree_sitter::{Node, TextProvider};
+
+// Adapter to convert rope chunks to bytes
+pub struct ChunksBytes<'a> {
+    chunks: ropey::iter::Chunks<'a>,
+}
+impl<'a> Iterator for ChunksBytes<'a> {
+    type Item = &'a [u8];
+    fn next(&mut self) -> Option<Self::Item> {
+        self.chunks.next().map(str::as_bytes)
+    }
+}
+
+pub struct RopeProvider<'a>(pub RopeSlice<'a>);
+
+impl<'a> TextProvider<&'a [u8]> for RopeProvider<'a> {
+    type I = ChunksBytes<'a>;
+
+    fn text(&mut self, node: Node) -> Self::I {
+        let fragment = self.0.byte_slice(node.start_byte()..node.end_byte());
+        ChunksBytes {
+            chunks: fragment.chunks(),
+        }
+    }
+}

helix-syntax/src/tree_cursor.rs

@@ -0,0 +1,264 @@
+use std::{cmp::Reverse, ops::Range};
+
+use super::{LanguageLayer, LayerId};
+
+use slotmap::HopSlotMap;
+use tree_sitter::Node;
+
+/// The byte range of an injection layer.
+///
+/// Injection ranges may overlap, but all overlapping parts are subsets of their parent ranges.
+/// This allows us to sort the ranges ahead of time in order to efficiently find a range that
+/// contains a point with maximum depth.
+#[derive(Debug)]
+struct InjectionRange {
+    start: usize,
+    end: usize,
+    layer_id: LayerId,
+    depth: u32,
+}
+
+pub struct TreeCursor<'a> {
+    layers: &'a HopSlotMap<LayerId, LanguageLayer>,
+    root: LayerId,
+    current: LayerId,
+    injection_ranges: Vec<InjectionRange>,
+    // TODO: Ideally this would be a `tree_sitter::TreeCursor<'a>` but
+    // that returns very surprising results in testing.
+    cursor: Node<'a>,
+}
+
+impl<'a> TreeCursor<'a> {
+    pub(super) fn new(layers: &'a HopSlotMap<LayerId, LanguageLayer>, root: LayerId) -> Self {
+        let mut injection_ranges = Vec::new();
+
+        for (layer_id, layer) in layers.iter() {
+            // Skip the root layer
+            if layer.parent.is_none() {
+                continue;
+            }
+            for byte_range in layer.ranges.iter() {
+                let range = InjectionRange {
+                    start: byte_range.start_byte,
+                    end: byte_range.end_byte,
+                    layer_id,
+                    depth: layer.depth,
+                };
+                injection_ranges.push(range);
+            }
+        }
+
+        injection_ranges.sort_unstable_by_key(|range| (range.end, Reverse(range.depth)));
+
+        let cursor = layers[root].tree().root_node();
+
+        Self {
+            layers,
+            root,
+            current: root,
+            injection_ranges,
+            cursor,
+        }
+    }
+
+    pub fn node(&self) -> Node<'a> {
+        self.cursor
+    }
+
+    pub fn goto_parent(&mut self) -> bool {
+        if let Some(parent) = self.node().parent() {
+            self.cursor = parent;
+            return true;
+        }
+
+        // If we are already on the root layer, we cannot ascend.
+        if self.current == self.root {
+            return false;
+        }
+
+        // Ascend to the parent layer.
+        let range = self.node().byte_range();
+        let parent_id = self.layers[self.current]
+            .parent
+            .expect("non-root layers have a parent");
+        self.current = parent_id;
+        let root = self.layers[self.current].tree().root_node();
+        self.cursor = root
+            .descendant_for_byte_range(range.start, range.end)
+            .unwrap_or(root);
+
+        true
+    }
+
+    pub fn goto_parent_with<P>(&mut self, predicate: P) -> bool
+    where
+        P: Fn(&Node) -> bool,
+    {
+        while self.goto_parent() {
+            if predicate(&self.node()) {
+                return true;
+            }
+        }
+
+        false
+    }
+
+    /// Finds the injection layer that has exactly the same range as the given `range`.
+    fn layer_id_of_byte_range(&self, search_range: Range<usize>) -> Option<LayerId> {
+        let start_idx = self
+            .injection_ranges
+            .partition_point(|range| range.end < search_range.end);
+
+        self.injection_ranges[start_idx..]
+            .iter()
+            .take_while(|range| range.end == search_range.end)
+            .find_map(|range| (range.start == search_range.start).then_some(range.layer_id))
+    }
+
+    fn goto_first_child_impl(&mut self, named: bool) -> bool {
+        // Check if the current node's range is an exact injection layer range.
+        if let Some(layer_id) = self
+            .layer_id_of_byte_range(self.node().byte_range())
+            .filter(|&layer_id| layer_id != self.current)
+        {
+            // Switch to the child layer.
+            self.current = layer_id;
+            self.cursor = self.layers[self.current].tree().root_node();
+            return true;
+        }
+
+        let child = if named {
+            self.cursor.named_child(0)
+        } else {
+            self.cursor.child(0)
+        };
+
+        if let Some(child) = child {
+            // Otherwise descend in the current tree.
+            self.cursor = child;
+            true
+        } else {
+            false
+        }
+    }
+
+    pub fn goto_first_child(&mut self) -> bool {
+        self.goto_first_child_impl(false)
+    }
+
+    pub fn goto_first_named_child(&mut self) -> bool {
+        self.goto_first_child_impl(true)
+    }
+
+    fn goto_next_sibling_impl(&mut self, named: bool) -> bool {
+        let sibling = if named {
+            self.cursor.next_named_sibling()
+        } else {
+            self.cursor.next_sibling()
+        };
+
+        if let Some(sibling) = sibling {
+            self.cursor = sibling;
+            true
+        } else {
+            false
+        }
+    }
+
+    pub fn goto_next_sibling(&mut self) -> bool {
+        self.goto_next_sibling_impl(false)
+    }
+
+    pub fn goto_next_named_sibling(&mut self) -> bool {
+        self.goto_next_sibling_impl(true)
+    }
+
+    fn goto_prev_sibling_impl(&mut self, named: bool) -> bool {
+        let sibling = if named {
+            self.cursor.prev_named_sibling()
+        } else {
+            self.cursor.prev_sibling()
+        };
+
+        if let Some(sibling) = sibling {
+            self.cursor = sibling;
+            true
+        } else {
+            false
+        }
+    }
+
+    pub fn goto_prev_sibling(&mut self) -> bool {
+        self.goto_prev_sibling_impl(false)
+    }
+
+    pub fn goto_prev_named_sibling(&mut self) -> bool {
+        self.goto_prev_sibling_impl(true)
+    }
+
+    /// Finds the injection layer that contains the given start-end range.
+    fn layer_id_containing_byte_range(&self, start: usize, end: usize) -> LayerId {
+        let start_idx = self
+            .injection_ranges
+            .partition_point(|range| range.end < end);
+
+        self.injection_ranges[start_idx..]
+            .iter()
+            .take_while(|range| range.start < end)
+            .find_map(|range| (range.start <= start).then_some(range.layer_id))
+            .unwrap_or(self.root)
+    }
+
+    pub fn reset_to_byte_range(&mut self, start: usize, end: usize) {
+        self.current = self.layer_id_containing_byte_range(start, end);
+        let root = self.layers[self.current].tree().root_node();
+        self.cursor = root.descendant_for_byte_range(start, end).unwrap_or(root);
+    }
+
+    /// Returns an iterator over the children of the node the TreeCursor is on
+    /// at the time this is called.
+    pub fn children(&'a mut self) -> ChildIter {
+        let parent = self.node();
+
+        ChildIter {
+            cursor: self,
+            parent,
+            named: false,
+        }
+    }
+
+    /// Returns an iterator over the named children of the node the TreeCursor is on
+    /// at the time this is called.
+    pub fn named_children(&'a mut self) -> ChildIter {
+        let parent = self.node();
+
+        ChildIter {
+            cursor: self,
+            parent,
+            named: true,
+        }
+    }
+}
+
+pub struct ChildIter<'n> {
+    cursor: &'n mut TreeCursor<'n>,
+    parent: Node<'n>,
+    named: bool,
+}
+
+impl<'n> Iterator for ChildIter<'n> {
+    type Item = Node<'n>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        // first iteration, just visit the first child
+        if self.cursor.node() == self.parent {
+            self.cursor
+                .goto_first_child_impl(self.named)
+                .then(|| self.cursor.node())
+        } else {
+            self.cursor
+                .goto_next_sibling_impl(self.named)
+                .then(|| self.cursor.node())
+        }
+    }
+}

helix-term/src/ui/markdown.rs

@@ -54,7 +54,14 @@ pub fn highlighted_code_block<'a>(
             language.into(),
         ))
         .and_then(|config| config.highlight_config(theme.scopes()))
-        .and_then(|config| Syntax::new(ropeslice, config, Arc::clone(&config_loader)));
+        .and_then(|config| {
+            Syntax::new(ropeslice, config, |injection| {
+                config_loader
+                    .load()
+                    .language_configuration_for_injection_string(injection)
+                    .and_then(|config| config.get_highlight_config())
+            })
+        });
 
     let syntax = match syntax {
         Some(s) => s,

helix-term/src/ui/picker/handlers.rs

@@ -82,7 +82,12 @@ fn finish_debounce(&mut self) {
                 let Some(syntax) = language_config
                     .highlight_config(&loader.load().scopes())
                     .and_then(|highlight_config| {
-                        helix_core::Syntax::new(text.slice(..), highlight_config, loader)
+                        helix_core::Syntax::new(text.slice(..), highlight_config, |injection| {
+                            loader
+                                .load()
+                                .language_configuration_for_injection_string(injection)
+                                .and_then(|config| config.get_highlight_config())
+                        })
                     })
                 else {
                     log::info!("highlighting picker item failed");

helix-view/src/document.rs

@@ -7,7 +7,7 @@
 use helix_core::chars::char_is_word;
 use helix_core::doc_formatter::TextFormat;
 use helix_core::encoding::Encoding;
-use helix_core::syntax::{Highlight, LanguageServerFeature};
+use helix_core::syntax::{generate_edits, Highlight, LanguageServerFeature};
 use helix_core::text_annotations::{InlineAnnotation, Overlay};
 use helix_lsp::util::lsp_pos_to_pos;
 use helix_stdx::faccess::{copy_metadata, readonly};
@@ -156,6 +156,7 @@ pub struct Document {
     pub syntax: Option<Syntax>,
     /// Corresponding language scope name. Usually `source.<lang>`.
     pub language: Option<Arc<LanguageConfiguration>>,
+    loader: Option<Arc<ArcSwap<helix_core::syntax::Loader>>>,
 
     /// Pending changes since last history commit.
     changes: ChangeSet,
@@ -678,6 +679,7 @@ pub fn from(
             focused_at: std::time::Instant::now(),
             readonly: false,
             jump_labels: HashMap::new(),
+            loader: None,
         }
     }
 
@@ -1131,9 +1133,15 @@ pub fn set_language(
             if let Some(highlight_config) =
                 language_config.highlight_config(&(*loader).load().scopes())
             {
-                self.syntax = Syntax::new(self.text.slice(..), highlight_config, loader);
+                let loader_ = loader.load_full();
+                self.syntax = Syntax::new(self.text.slice(..), highlight_config, |injection| {
+                    loader_
+                        .language_configuration_for_injection_string(injection)
+                        .and_then(|config| config.get_highlight_config())
+                });
             }
 
+            self.loader = Some(loader);
             self.language = Some(language_config);
         } else {
             self.syntax = None;
@@ -1275,11 +1283,16 @@ fn apply_impl(
 
             // update tree-sitter syntax tree
             if let Some(syntax) = &mut self.syntax {
+                let loader = self.loader.as_ref().unwrap().load_full();
                 // TODO: no unwrap
                 let res = syntax.update(
-                    old_doc.slice(..),
                     self.text.slice(..),
-                    transaction.changes(),
+                    generate_edits(old_doc.slice(..), transaction.changes()),
+                    |injection| {
+                        loader
+                            .language_configuration_for_injection_string(injection)
+                            .and_then(|config| config.get_highlight_config())
+                    },
                 );
                 if res.is_err() {
                     log::error!("TS parser failed, disabling TS for the current buffer: {res:?}");