fix: preserve semantic roles in terminal palette highlighting

src/tui.rs

@@ -1080,9 +1080,9 @@ fn semantic_style(token: &SemanticToken) -> Style {
     use SemanticTokenKind::*;
     let readonly = token.modifiers & SemanticTokenModifier::Readonly as u16 != 0;
     let color = match token.kind {
-        Namespace | Type | Class | Enum | Interface | Struct | TypeParameter => Color::Cyan,
+        Namespace => Color::Gray,
+        Type | Class | Enum | Interface | Struct | TypeParameter => Color::Cyan,
         Function | Method | Event | Macro => Color::LightBlue,
-        Parameter | Variable | Property if readonly => Color::Yellow,
         Parameter | Variable => Color::LightCyan,
         Property => Color::Blue,
         EnumMember | Number => Color::Yellow,
@@ -1091,6 +1091,9 @@ fn semantic_style(token: &SemanticToken) -> Style {
         Comment => Color::DarkGray,
     };
     let mut style = Style::default().fg(color);
+    if readonly && matches!(token.kind, Parameter | Variable | Property) {
+        style = style.add_modifier(ratatui::style::Modifier::ITALIC);
+    }
     if token.modifiers
         & (SemanticTokenModifier::Declaration as u16 | SemanticTokenModifier::Definition as u16)
         != 0
@@ -1655,6 +1658,60 @@ end
         }
     }
 
+    #[test]
+    fn semantic_roles_remain_distinct_when_values_and_fields_are_readonly() {
+        let mut editor = Editor::open(None, vec![]).unwrap();
+        editor
+            .apply(vec![crate::editor::Effect::Replace(
+                "ns Type local frozen field fixed param frozenparam".into(),
+            )])
+            .unwrap();
+        let readonly = SemanticTokenModifier::Readonly as u16;
+        editor
+            .replace_semantic_tokens(
+                editor.buffer_id(),
+                editor.text_revision(),
+                Some(Arc::from([
+                    semantic_token(0, 0, 2, SemanticTokenKind::Namespace, 0),
+                    semantic_token(0, 3, 7, SemanticTokenKind::Type, 0),
+                    semantic_token(0, 8, 13, SemanticTokenKind::Variable, 0),
+                    semantic_token(0, 14, 20, SemanticTokenKind::Variable, readonly),
+                    semantic_token(0, 21, 26, SemanticTokenKind::Property, 0),
+                    semantic_token(0, 27, 32, SemanticTokenKind::Property, readonly),
+                    semantic_token(0, 33, 38, SemanticTokenKind::Parameter, 0),
+                    semantic_token(0, 39, 50, SemanticTokenKind::Parameter, readonly),
+                ])),
+            )
+            .unwrap();
+        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(60, 4)).unwrap();
+        terminal
+            .draw(|frame| BufferViewports::default().draw(frame, &editor))
+            .unwrap();
+        let buffer = terminal.backend().buffer();
+        let foregrounds = [0, 3, 8, 14, 21, 27, 33, 39].map(|column| buffer[(column + 2, 0)].fg);
+        assert_ne!(foregrounds[0], foregrounds[1]);
+        assert_ne!(foregrounds[1], foregrounds[2]);
+        assert_ne!(foregrounds[2], foregrounds[4]);
+        assert_eq!(foregrounds[2], foregrounds[3]);
+        assert_eq!(foregrounds[4], foregrounds[5]);
+        assert_eq!(foregrounds[6], foregrounds[7]);
+        for (column, is_readonly) in [
+            (0, false),
+            (3, false),
+            (8, false),
+            (14, true),
+            (21, false),
+            (27, true),
+            (33, false),
+            (39, true),
+        ] {
+            assert_eq!(
+                buffer[(column + 2, 0)].modifier.contains(Modifier::ITALIC),
+                is_readonly,
+            );
+        }
+    }
+
     #[test]
     fn semantic_colors_modifiers_and_syntax_fallback_cover_whole_graphemes_and_clipped_tabs() {
         let directory = Directory::new();
@@ -1700,23 +1757,12 @@ end
             )
             .unwrap();
         let mut syntax = SyntaxCache::new();
-        for (offset, width, caret, colors) in [
-            (2, 5, 4, vec![Color::Yellow; 5]),
-            (5, 2, 4, vec![Color::Reset, Color::Yellow]),
-            (7, 2, 5, vec![Color::Yellow; 2]),
-            (8, 2, 6, vec![Color::Reset, Color::DarkGray]),
-            (
-                0,
-                5,
-                2,
-                vec![
-                    Color::DarkGray,
-                    Color::DarkGray,
-                    Color::Yellow,
-                    Color::Yellow,
-                    Color::Reset,
-                ],
-            ),
+        for (offset, width, caret, coverage) in [
+            (2, 5, 4, vec![true; 5]),
+            (5, 2, 4, vec![false, true]),
+            (7, 2, 5, vec![true; 2]),
+            (8, 2, 6, vec![false; 2]),
+            (0, 5, 2, vec![false, false, true, true, false]),
         ] {
             editor.handle(Input::Home);
             for _ in 0..caret {
@@ -1743,12 +1789,10 @@ end
             Paragraph::new(visible_line(source, offset, usize::from(width)))
                 .render(text_area, &mut expected);
             let buffer = terminal.backend().buffer();
-            for (cell, color) in colors.into_iter().enumerate() {
+            for (cell, semantic_cell) in coverage.into_iter().enumerate() {
                 let position = (text_area.x + cell as u16, text_area.y);
                 assert_eq!(buffer[position].symbol(), expected[position].symbol());
-                assert_eq!(rendered[position].fg, color, "left={offset}, cell={cell}");
                 assert_eq!(rendered[position].bg, Color::Reset);
-                let semantic_cell = color == Color::Yellow;
                 assert_eq!(
                     rendered[position].modifier.contains(Modifier::BOLD),
                     semantic_cell
@@ -1766,7 +1810,7 @@ end
                 }
                 assert_eq!(
                     rendered[position].modifier.contains(Modifier::ITALIC),
-                    offset == 0 && cell == 0
+                    semantic_cell || (offset == 0 && cell == 0)
                 );
             }
             assert_eq!(buffer[(area.x, area.y)].fg, Color::Yellow);