Add diff-aware color fallback to preserve compare highlighting

Author: jonaraphael

README.md

@@ -100,6 +100,7 @@ Global (Settings UI or `settings.json`):
 - `csv.cellPadding` (number, default `4`): Vertical cell padding in pixels.
 - `csv.columnColorMode` (string, default `type`): `type` keeps CSV’s type-based column colors; `theme` uses your theme foreground color for all columns.
 - `csv.columnColorPalette` (string, default `default`): Type-color palette when `csv.columnColorMode` is `type`. `cool` biases colors toward greens/blues; `warm` biases colors toward oranges/reds.
+- `csv.diffUseThemeForeground` (boolean, default `true`): In compare/diff views, use theme foreground color so diff highlighting remains readable.
 - `csv.clickableLinks` (boolean, default `true`): Make URLs in cells clickable. Ctrl/Cmd+click to open links.
 - `csv.showTrailingEmptyRow` (boolean, default `true`): Show the extra empty row at the end of the table. Turn this off to hide that visual append row.
 - `csv.separatorMode` (string, default `extension`): Separator selection mode when no per-file override exists. `extension` uses extension mapping, `auto` detects from content first, `default` always uses `csv.defaultSeparator`.

package.json

@@ -140,6 +140,11 @@
           "default": "default",
           "description": "Type-color palette when csv.columnColorMode is 'type'. 'default' keeps the original palette, 'cool' biases colors toward greens/blues, and 'warm' biases colors toward oranges/reds."
         },
+        "csv.diffUseThemeForeground": {
+          "type": "boolean",
+          "default": true,
+          "description": "When CSV is opened in a diff/compare view, use the current theme foreground color for cell text so diff highlighting stays visible."
+        },
         "csv.clickableLinks": {
           "type": "boolean",
           "default": true,

src/CsvEditorProvider.ts

@@ -28,6 +28,7 @@ class CsvEditorController {
   private currentWebviewPanel: vscode.WebviewPanel | undefined;
   private document!: vscode.TextDocument;
   private separatorCache: { version: number; configKey: string; separator: string } | undefined;
+  private isDiffContext = false;
 
   constructor(private readonly context: vscode.ExtensionContext) {}
 
@@ -61,6 +62,7 @@ class CsvEditorController {
       localResourceRoots: [vscode.Uri.file(path.join(this.context.extensionPath, 'media'))]
     };
 
+    this.refreshDiffContext(webviewPanel);
     this.updateWebviewContent();
 
     if (webviewPanel.active) {
@@ -70,6 +72,10 @@ class CsvEditorController {
     webviewPanel.webview.postMessage({ type: 'focus' });
     webviewPanel.onDidChangeViewState(e => {
       if (e.webviewPanel.active) {
+        const diffChanged = this.refreshDiffContext(e.webviewPanel);
+        if (diffChanged) {
+          this.updateWebviewContent();
+        }
         e.webviewPanel.webview.postMessage({ type: 'focus' });
         CsvEditorProvider.currentActive = this;
       }
@@ -270,6 +276,54 @@ class CsvEditorController {
     return !!this.currentWebviewPanel?.active;
   }
 
+  private refreshDiffContext(webviewPanel: vscode.WebviewPanel): boolean {
+    const next = this.isLikelyDiffContext(webviewPanel, this.document.uri);
+    const changed = next !== this.isDiffContext;
+    this.isDiffContext = next;
+    return changed;
+  }
+
+  private isLikelyDiffContext(webviewPanel: vscode.WebviewPanel, uri: vscode.Uri): boolean {
+    if (uri.scheme === 'git') {
+      return true;
+    }
+
+    const title = webviewPanel.title || '';
+    if (title.includes('↔')) {
+      return true;
+    }
+
+    const key = uri.toString();
+    const tabGroups = (vscode.window as any)?.tabGroups?.all;
+    if (!Array.isArray(tabGroups)) {
+      return false;
+    }
+    for (const group of tabGroups) {
+      const activeTab: any = group?.activeTab;
+      const input: any = activeTab?.input;
+      const original: unknown = input?.original;
+      const modified: unknown = input?.modified;
+      if (original instanceof vscode.Uri && modified instanceof vscode.Uri) {
+        if (original.toString() === key || modified.toString() === key) {
+          return true;
+        }
+      }
+    }
+    return false;
+  }
+
+  private static resolveEffectiveColumnColorMode(
+    baseMode: string,
+    isDiffContext: boolean,
+    useThemeForegroundInDiff: boolean
+  ): 'type' | 'theme' {
+    const normalizedBase: 'type' | 'theme' = baseMode === 'theme' ? 'theme' : 'type';
+    if (isDiffContext && useThemeForegroundInDiff) {
+      return 'theme';
+    }
+    return normalizedBase;
+  }
+
   public getDocumentUri(): vscode.Uri {
     return this.document.uri;
   }
@@ -974,7 +1028,13 @@ class CsvEditorController {
     const data = this.trimTrailingEmptyRows((parsed.data || []) as string[][]);
     const treatHeader = this.getEffectiveHeader(data, hiddenRows);
     const clickableLinks = config.get<boolean>('clickableLinks', true);
-    const columnColorMode = config.get<string>('columnColorMode', 'type');
+    const configuredColumnColorMode = config.get<string>('columnColorMode', 'type');
+    const diffUseThemeForeground = config.get<boolean>('diffUseThemeForeground', true);
+    const columnColorMode = CsvEditorController.resolveEffectiveColumnColorMode(
+      configuredColumnColorMode,
+      this.isDiffContext,
+      diffUseThemeForeground
+    );
     const columnColorPalette = config.get<string>('columnColorPalette', 'default');
     const showTrailingEmptyRow = config.get<boolean>('showTrailingEmptyRow', true);
 
@@ -2216,6 +2276,9 @@ export class CsvEditorProvider implements vscode.CustomTextEditorProvider {
       const c: any = new (CsvEditorController as any)({} as any);
       return c.getColumnColor(t, dark, i, palette);
     },
+    resolveEffectiveColumnColorMode(baseMode: string, isDiffContext: boolean, diffUseThemeForeground: boolean): 'type' | 'theme' {
+      return (CsvEditorController as any).resolveEffectiveColumnColorMode(baseMode, isDiffContext, diffUseThemeForeground);
+    },
     hslToHex(h: number, s: number, l: number): string {
       const c: any = new (CsvEditorController as any)({} as any);
       return c.hslToHex(h, s, l);

src/extension.ts

@@ -91,7 +91,9 @@ export function activate(context: vscode.ExtensionContext) {
       'csv.cellPadding',
       'csv.columnColorMode',
       'csv.columnColorPalette',
+      'csv.diffUseThemeForeground',
       'csv.clickableLinks',
+      'csv.showTrailingEmptyRow',
       'csv.separatorMode',
       'csv.defaultSeparator',
       'csv.separatorByExtension'

src/test/provider-utils.test.ts

@@ -138,6 +138,16 @@ describe('CsvEditorProvider utility methods', () => {
     assert.notStrictEqual(def, warm);
   });
 
+  it('resolves effective column color mode for diff contexts', () => {
+    const resolveMode = CsvEditorProvider.__test.resolveEffectiveColumnColorMode;
+    assert.strictEqual(resolveMode('type', false, true), 'type');
+    assert.strictEqual(resolveMode('theme', false, true), 'theme');
+    assert.strictEqual(resolveMode('type', true, true), 'theme');
+    assert.strictEqual(resolveMode('theme', true, true), 'theme');
+    assert.strictEqual(resolveMode('type', true, false), 'type');
+    assert.strictEqual(resolveMode('invalid', false, false), 'type');
+  });
+
   it('hslToHex converts known colors', () => {
     const hslToHex = CsvEditorProvider.__test.hslToHex;
     assert.strictEqual(hslToHex(0, 100, 50), '#ff0000');   // red