fix(vscode-ide-companion): use existing editor group for diff instead of forcing a new one

packages/vscode-ide-companion/src/diff-manager.ts

@@ -14,7 +14,7 @@ import * as vscode from 'vscode';
 import { DIFF_SCHEME } from './extension.js';
 import {
   findLeftGroupOfChatWebview,
-  ensureLeftGroupOfChatWebview,
+  findRightGroupOfChatWebview,
 } from './utils/editorGroupUtils.js';
 
 export class DiffContentProvider implements vscode.TextDocumentContentProvider {
@@ -222,28 +222,22 @@ export class DiffManager {
       true,
     );
 
-    // Prefer opening the diff adjacent to the chat webview (so we don't
-    // replace content inside the locked webview group). We try the group to
-    // the left of the chat webview first; if none exists we fall back to
-    // ViewColumn.Beside. With the chat locked in the leftmost group, this
-    // fallback opens diffs to the right of the chat.
-    let targetViewColumn = findLeftGroupOfChatWebview();
-    if (targetViewColumn === undefined) {
-      // If there is no left neighbor, create one to satisfy the requirement of
-      // opening diffs to the left of the chat webview.
-      targetViewColumn = await ensureLeftGroupOfChatWebview();
-    }
+    // Prefer opening the diff in the group to the left of the chat webview.
+    // When that isn't available (e.g. chat is in the leftmost group), try the
+    // group to the right so we reuse existing layout. Only fall back to
+    // ViewColumn.Beside when neither neighbor exists or the webview is missing.
+    const targetViewColumn =
+      findLeftGroupOfChatWebview() ??
+      findRightGroupOfChatWebview() ??
+      vscode.ViewColumn.Beside;
 
     await vscode.commands.executeCommand(
       'vscode.diff',
       leftDocUri,
       rightDocUri,
       diffTitle,
       {
-        // If a left-of-webview group was found, target it explicitly so the
-        // diff opens there while keeping focus on the webview. Otherwise, use
-        // the default "open to side" behavior.
-        viewColumn: targetViewColumn ?? vscode.ViewColumn.Beside,
+        viewColumn: targetViewColumn,
         preview: false,
         preserveFocus: true,
       },

packages/vscode-ide-companion/src/utils/editorGroupUtils.test.ts

@@ -0,0 +1,175 @@
+/**
+ * @license
+ * Copyright 2025 Qwen Team
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+
+const chatViewType = 'mainThreadWebview-qwenCode.chat';
+
+const vscodeMock = vi.hoisted(() => ({
+  ViewColumn: { One: 1, Two: 2, Three: 3, Four: 4 },
+  window: {
+    tabGroups: {
+      all: [] as Array<{ tabs: Array<{ input: unknown }>; viewColumn: number }>,
+    },
+  },
+}));
+
+vi.mock('vscode', () => vscodeMock);
+
+import {
+  findLeftGroupOfChatWebview,
+  findRightGroupOfChatWebview,
+} from './editorGroupUtils.js';
+
+function chatTab() {
+  return { input: { viewType: chatViewType } };
+}
+
+function regularTab() {
+  return { input: { viewType: 'default' } };
+}
+
+describe('findLeftGroupOfChatWebview', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    vscodeMock.window.tabGroups.all = [];
+  });
+
+  it('returns the nearest left neighbor when chat webview has a group to its left', () => {
+    vscodeMock.window.tabGroups.all = [
+      { tabs: [regularTab()], viewColumn: 1 },
+      { tabs: [chatTab()], viewColumn: 2 },
+      { tabs: [regularTab()], viewColumn: 3 },
+    ];
+
+    expect(findLeftGroupOfChatWebview()).toBe(1);
+  });
+
+  it('returns the closest left neighbor when multiple left groups exist', () => {
+    vscodeMock.window.tabGroups.all = [
+      { tabs: [regularTab()], viewColumn: 1 },
+      { tabs: [regularTab()], viewColumn: 2 },
+      { tabs: [chatTab()], viewColumn: 4 },
+      { tabs: [regularTab()], viewColumn: 5 },
+    ];
+
+    // closest left is group 2, not group 1
+    expect(findLeftGroupOfChatWebview()).toBe(2);
+  });
+
+  it('returns undefined when chat webview is in the leftmost group', () => {
+    vscodeMock.window.tabGroups.all = [
+      { tabs: [chatTab()], viewColumn: 1 },
+      { tabs: [regularTab()], viewColumn: 2 },
+    ];
+
+    expect(findLeftGroupOfChatWebview()).toBeUndefined();
+  });
+
+  it('returns undefined when no chat webview is found', () => {
+    vscodeMock.window.tabGroups.all = [
+      { tabs: [regularTab()], viewColumn: 1 },
+      { tabs: [regularTab()], viewColumn: 2 },
+    ];
+
+    expect(findLeftGroupOfChatWebview()).toBeUndefined();
+  });
+
+  it('returns undefined when there are no tab groups', () => {
+    vscodeMock.window.tabGroups.all = [];
+
+    expect(findLeftGroupOfChatWebview()).toBeUndefined();
+  });
+
+  it('returns undefined when tabGroups access throws', () => {
+    // make .all throw on access
+    Object.defineProperty(vscodeMock.window.tabGroups, 'all', {
+      get: () => {
+        throw new Error('unexpected error');
+      },
+      configurable: true,
+    });
+
+    expect(findLeftGroupOfChatWebview()).toBeUndefined();
+
+    // restore
+    Object.defineProperty(vscodeMock.window.tabGroups, 'all', {
+      value: [],
+      configurable: true,
+      writable: true,
+    });
+  });
+});
+
+describe('findRightGroupOfChatWebview', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    vscodeMock.window.tabGroups.all = [];
+  });
+
+  it('returns the nearest right neighbor when chat webview has a group to its right', () => {
+    vscodeMock.window.tabGroups.all = [
+      { tabs: [regularTab()], viewColumn: 1 },
+      { tabs: [chatTab()], viewColumn: 2 },
+      { tabs: [regularTab()], viewColumn: 3 },
+    ];
+
+    expect(findRightGroupOfChatWebview()).toBe(3);
+  });
+
+  it('returns the closest right neighbor when multiple right groups exist', () => {
+    vscodeMock.window.tabGroups.all = [
+      { tabs: [regularTab()], viewColumn: 1 },
+      { tabs: [chatTab()], viewColumn: 2 },
+      { tabs: [regularTab()], viewColumn: 3 },
+      { tabs: [regularTab()], viewColumn: 5 },
+    ];
+
+    // closest right is group 3, not group 5
+    expect(findRightGroupOfChatWebview()).toBe(3);
+  });
+
+  it('returns undefined when chat webview is in the rightmost group', () => {
+    vscodeMock.window.tabGroups.all = [
+      { tabs: [regularTab()], viewColumn: 1 },
+      { tabs: [chatTab()], viewColumn: 3 },
+    ];
+
+    expect(findRightGroupOfChatWebview()).toBeUndefined();
+  });
+
+  it('returns undefined when no chat webview is found', () => {
+    vscodeMock.window.tabGroups.all = [
+      { tabs: [regularTab()], viewColumn: 1 },
+      { tabs: [regularTab()], viewColumn: 2 },
+    ];
+
+    expect(findRightGroupOfChatWebview()).toBeUndefined();
+  });
+
+  it('returns undefined when there are no tab groups', () => {
+    vscodeMock.window.tabGroups.all = [];
+
+    expect(findRightGroupOfChatWebview()).toBeUndefined();
+  });
+
+  it('returns undefined when tabGroups access throws', () => {
+    Object.defineProperty(vscodeMock.window.tabGroups, 'all', {
+      get: () => {
+        throw new Error('unexpected error');
+      },
+      configurable: true,
+    });
+
+    expect(findRightGroupOfChatWebview()).toBeUndefined();
+
+    Object.defineProperty(vscodeMock.window.tabGroups, 'all', {
+      value: [],
+      configurable: true,
+      writable: true,
+    });
+  });
+});