Support LSP diagnostic tags (#9780)

book/src/themes.md

@@ -333,5 +333,7 @@ #### Interface
 | `diagnostic.info`                 | Diagnostics info (editing area)                                                                |
 | `diagnostic.warning`              | Diagnostics warning (editing area)                                                             |
 | `diagnostic.error`                | Diagnostics error (editing area)                                                               |
+| `diagnostic.unnecessary`          | Diagnostics with unnecessary tag (editing area)                                                |
+| `diagnostic.deprecated`           | Diagnostics with deprecated tag (editing area)                                                 |
 
 [editor-section]: ./configuration.md#editor-section

helix-lsp/src/client.rs

@@ -631,6 +631,12 @@ pub(crate) async fn initialize(&self, enable_snippets: bool) -> Result<lsp::Init
                     }),
                     publish_diagnostics: Some(lsp::PublishDiagnosticsClientCapabilities {
                         version_support: Some(true),
+                        tag_support: Some(lsp::TagSupport {
+                            value_set: vec![
+                                lsp::DiagnosticTag::UNNECESSARY,
+                                lsp::DiagnosticTag::DEPRECATED,
+                            ],
+                        }),
                         ..Default::default()
                     }),
                     inlay_hint: Some(lsp::InlayHintClientCapabilities {

helix-term/src/ui/editor.rs

@@ -360,7 +360,7 @@ pub fn doc_diagnostics_highlights(
         doc: &Document,
         theme: &Theme,
     ) -> [Vec<(usize, std::ops::Range<usize>)>; 5] {
-        use helix_core::diagnostic::Severity;
+        use helix_core::diagnostic::{DiagnosticTag, Severity};
         let get_scope_of = |scope| {
             theme
             .find_scope_index_exact(scope)
@@ -380,6 +380,10 @@ pub fn doc_diagnostics_highlights(
         let error = get_scope_of("diagnostic.error");
         let r#default = get_scope_of("diagnostic"); // this is a bit redundant but should be fine
 
+        // Diagnostic tags
+        let unnecessary = theme.find_scope_index_exact("diagnostic.unnecessary");
+        let deprecated = theme.find_scope_index_exact("diagnostic.deprecated");
+
         let mut default_vec: Vec<(usize, std::ops::Range<usize>)> = Vec::new();
         let mut info_vec = Vec::new();
         let mut hint_vec = Vec::new();
@@ -396,6 +400,15 @@ pub fn doc_diagnostics_highlights(
                 _ => (&mut default_vec, r#default),
             };
 
+            let scope = diagnostic
+                .tags
+                .first()
+                .and_then(|tag| match tag {
+                    DiagnosticTag::Unnecessary => unnecessary,
+                    DiagnosticTag::Deprecated => deprecated,
+                })
+                .unwrap_or(scope);
+
             // If any diagnostic overlaps ranges with the prior diagnostic,
             // merge the two together. Otherwise push a new span.
             match vec.last_mut() {

theme.toml

@@ -80,6 +80,8 @@ label = "honey"
 "diagnostic.info" = { underline = { color = "delta", style = "curl" } }
 "diagnostic.warning" = { underline = { color = "lightning", style = "curl" } }
 "diagnostic.error" = { underline = { color = "apricot", style = "curl" } }
+"diagnostic.unnecessary" = { modifiers = ["dim"] }
+"diagnostic.deprecated" = { modifiers = ["crossed_out"] }
 
 warning = "lightning"
 error = "apricot"