fix: resolve diff editor timeout issue when file is pre-opened

- Add immediate check for visible diff editor after command execution
- Handles cases where document open events may not fire for pre-opened files
- Fixes timeout error "Failed to open diff editor within 10 seconds"
- Add test to verify the fix works correctly

Fixes #6199

src/integrations/editor/DiffViewProvider.ts

@@ -187,7 +187,10 @@ export class DiffViewProvider {
 		}
 	}
 
-	async saveChanges(diagnosticsEnabled: boolean = true, writeDelayMs: number = DEFAULT_WRITE_DELAY_MS): Promise<{
+	async saveChanges(
+		diagnosticsEnabled: boolean = true,
+		writeDelayMs: number = DEFAULT_WRITE_DELAY_MS,
+	): Promise<{
 		newProblemsMessage: string | undefined
 		userEdits: string | undefined
 		finalContent: string | undefined
@@ -222,22 +225,22 @@ export class DiffViewProvider {
 		// and can address them accordingly. If problems don't change immediately after
 		// applying a fix, won't be notified, which is generally fine since the
 		// initial fix is usually correct and it may just take time for linters to catch up.
-		
+
 		let newProblemsMessage = ""
-		
+
 		if (diagnosticsEnabled) {
 			// Add configurable delay to allow linters time to process and clean up issues
 			// like unused imports (especially important for Go and other languages)
 			// Ensure delay is non-negative
 			const safeDelayMs = Math.max(0, writeDelayMs)
-			
+
 			try {
 				await delay(safeDelayMs)
 			} catch (error) {
 				// Log error but continue - delay failure shouldn't break the save operation
 				console.warn(`Failed to apply write delay: ${error}`)
 			}
-			
+
 			const postDiagnostics = vscode.languages.getDiagnostics()
 
 			// Get diagnostic settings from state
@@ -551,8 +554,21 @@ export class DiffViewProvider {
 					)
 				})
 				.then(
-					() => {
-						// Command executed successfully, now wait for the editor to appear
+					async () => {
+						// Command executed successfully, now check if the diff editor is already visible
+						// This handles cases where the document was pre-opened and events might not fire
+						await new Promise((r) => setTimeout(r, 100)) // Small delay to ensure UI updates
+
+						// Check if the diff editor is already visible
+						const diffEditor = vscode.window.visibleTextEditors.find((e) =>
+							arePathsEqual(e.document.uri.fsPath, uri.fsPath),
+						)
+
+						if (diffEditor) {
+							cleanup()
+							resolve(diffEditor)
+						}
+						// If not found immediately, the event listeners will handle it
 					},
 					(err: any) => {
 						cleanup()

src/integrations/editor/__tests__/DiffViewProvider.spec.ts

@@ -267,6 +267,62 @@ describe("DiffViewProvider", () => {
 				"Failed to execute diff command for /mock/cwd/test.md: Cannot open file",
 			)
 		})
+
+		it("should resolve immediately if diff editor is already visible after command", async () => {
+			// Setup
+			const mockEditor = {
+				document: {
+					uri: { fsPath: `${mockCwd}/test.md` },
+					getText: vi.fn().mockReturnValue(""),
+					lineCount: 0,
+				},
+				selection: {
+					active: { line: 0, character: 0 },
+					anchor: { line: 0, character: 0 },
+				},
+				edit: vi.fn().mockResolvedValue(true),
+				revealRange: vi.fn(),
+			}
+
+			// Mock showTextDocument
+			vi.mocked(vscode.window.showTextDocument).mockResolvedValue(mockEditor as any)
+
+			// Mock executeCommand to succeed
+			vi.mocked(vscode.commands.executeCommand).mockResolvedValue(undefined)
+
+			// Mock workspace.onDidOpenTextDocument - don't trigger callback
+			vi.mocked(vscode.workspace.onDidOpenTextDocument).mockReturnValue({ dispose: vi.fn() })
+
+			// Mock window.onDidChangeVisibleTextEditors - don't trigger callback
+			vi.mocked(vscode.window.onDidChangeVisibleTextEditors).mockReturnValue({ dispose: vi.fn() })
+
+			// Mock window.visibleTextEditors to return our editor immediately after command
+			vi.mocked(vscode.window).visibleTextEditors = [mockEditor as any]
+
+			// Set up for file
+			;(diffViewProvider as any).editType = "modify"
+
+			// Execute open - should complete successfully
+			await diffViewProvider.open("test.md")
+
+			// Verify that showTextDocument was called
+			expect(vscode.window.showTextDocument).toHaveBeenCalledWith(
+				expect.objectContaining({ fsPath: `${mockCwd}/test.md` }),
+				{ preview: false, viewColumn: vscode.ViewColumn.Active, preserveFocus: true },
+			)
+
+			// Verify that the diff command was executed
+			expect(vscode.commands.executeCommand).toHaveBeenCalledWith(
+				"vscode.diff",
+				expect.any(Object),
+				expect.any(Object),
+				`test.md: ${DIFF_VIEW_LABEL_CHANGES} (Editable)`,
+				{ preserveFocus: true },
+			)
+
+			// Verify that the activeDiffEditor was set
+			expect((diffViewProvider as any).activeDiffEditor).toBe(mockEditor)
+		})
 	})
 
 	describe("closeAllDiffViews method", () => {