Add emacs support, as per user requests. :) (#1633)

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>
Co-authored-by: N. Taylor Mullen <[email protected]>
Co-authored-by: Jacob Richman <[email protected]>
Co-authored-by: matt korwel <[email protected]>
Co-authored-by: matt korwel <[email protected]>

2 files changed, 36 insertions, 2 deletions

diff --git a/packages/core/src/utils/editor.test.ts b/packages/core/src/utils/editor.test.ts
index a86d6f59..203223ae 100644
--- a/packages/core/src/utils/editor.test.ts
+++ b/packages/core/src/utils/editor.test.ts
@@ -70,6 +70,7 @@ describe('editor utils', () => {
       { editor: 'vim', commands: ['vim'], win32Commands: ['vim'] },
       { editor: 'neovim', commands: ['nvim'], win32Commands: ['nvim'] },
       { editor: 'zed', commands: ['zed', 'zeditor'], win32Commands: ['zed'] },
+      { editor: 'emacs', commands: ['emacs'], win32Commands: ['emacs.exe'] },
     ];
 
     for (const { editor, commands, win32Commands } of testCases) {
@@ -297,6 +298,14 @@ describe('editor utils', () => {
       });
     }
 
+    it('should return the correct command for emacs', () => {
+      const command = getDiffCommand('old.txt', 'new.txt', 'emacs');
+      expect(command).toEqual({
+        command: 'emacs',
+        args: ['--eval', '(ediff "old.txt" "new.txt")'],
+      });
+    });
+
     it('should return null for an unsupported editor', () => {
       // @ts-expect-error Testing unsupported editor
       const command = getDiffCommand('old.txt', 'new.txt', 'foobar');
@@ -372,7 +381,7 @@ describe('editor utils', () => {
       });
     }
 
-    const execSyncEditors: EditorType[] = ['vim', 'neovim'];
+    const execSyncEditors: EditorType[] = ['vim', 'neovim', 'emacs'];
     for (const editor of execSyncEditors) {
       it(`should call execSync for ${editor} on non-windows`, async () => {
         Object.defineProperty(process, 'platform', { value: 'linux' });
@@ -425,6 +434,15 @@ describe('editor utils', () => {
       expect(allowEditorTypeInSandbox('vim')).toBe(true);
     });
 
+    it('should allow emacs in sandbox mode', () => {
+      process.env.SANDBOX = 'sandbox';
+      expect(allowEditorTypeInSandbox('emacs')).toBe(true);
+    });
+
+    it('should allow emacs when not in sandbox mode', () => {
+      expect(allowEditorTypeInSandbox('emacs')).toBe(true);
+    });
+
     it('should allow neovim in sandbox mode', () => {
       process.env.SANDBOX = 'sandbox';
       expect(allowEditorTypeInSandbox('neovim')).toBe(true);
@@ -490,6 +508,12 @@ describe('editor utils', () => {
       expect(isEditorAvailable('vim')).toBe(true);
     });
 
+    it('should return true for emacs when installed and in sandbox mode', () => {
+      (execSync as Mock).mockReturnValue(Buffer.from('/usr/bin/emacs'));
+      process.env.SANDBOX = 'sandbox';
+      expect(isEditorAvailable('emacs')).toBe(true);
+    });
+
     it('should return true for neovim when installed and in sandbox mode', () => {
       (execSync as Mock).mockReturnValue(Buffer.from('/usr/bin/nvim'));
       process.env.SANDBOX = 'sandbox';
diff --git a/packages/core/src/utils/editor.ts b/packages/core/src/utils/editor.ts
index 2d65d525..704d1cbb 100644
--- a/packages/core/src/utils/editor.ts
+++ b/packages/core/src/utils/editor.ts
@@ -13,7 +13,8 @@ export type EditorType =
   | 'cursor'
   | 'vim'
   | 'neovim'
-  | 'zed';
+  | 'zed'
+  | 'emacs';
 
 function isValidEditorType(editor: string): editor is EditorType {
   return [
@@ -24,6 +25,7 @@ function isValidEditorType(editor: string): editor is EditorType {
     'vim',
     'neovim',
     'zed',
+    'emacs',
   ].includes(editor);
 }
 
@@ -59,6 +61,7 @@ const editorCommands: Record<
   vim: { win32: ['vim'], default: ['vim'] },
   neovim: { win32: ['nvim'], default: ['nvim'] },
   zed: { win32: ['zed'], default: ['zed', 'zeditor'] },
+  emacs: { win32: ['emacs.exe'], default: ['emacs'] },
 };
 
 export function checkHasEditorType(editor: EditorType): boolean {
@@ -73,6 +76,7 @@ export function allowEditorTypeInSandbox(editor: EditorType): boolean {
   if (['vscode', 'vscodium', 'windsurf', 'cursor', 'zed'].includes(editor)) {
     return notUsingSandbox;
   }
+  // For terminal-based editors like vim and emacs, allow in sandbox.
   return true;
 }
 
@@ -141,6 +145,11 @@ export function getDiffCommand(
           newPath,
         ],
       };
+    case 'emacs':
+      return {
+        command: 'emacs',
+        args: ['--eval', `(ediff "${oldPath}" "${newPath}")`],
+      };
     default:
       return null;
   }
@@ -190,6 +199,7 @@ export async function openDiff(
         });
 
       case 'vim':
+      case 'emacs':
       case 'neovim': {
         // Use execSync for terminal-based editors
         const command =