feat: Add flow to allow modifying edits during edit tool call (#808)

1 files changed, 128 insertions, 0 deletions

diff --git a/packages/core/src/utils/editor.ts b/packages/core/src/utils/editor.ts
new file mode 100644
index 00000000..6f65d8da
--- /dev/null
+++ b/packages/core/src/utils/editor.ts
@@ -0,0 +1,128 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { execSync, spawn } from 'child_process';
+
+type EditorType = 'vscode' | 'vim';
+
+interface DiffCommand {
+  command: string;
+  args: string[];
+}
+
+export function checkHasEditor(editor: EditorType): boolean {
+  const commandExists = (cmd: string): boolean => {
+    try {
+      execSync(`which ${cmd}`, { stdio: 'ignore' });
+      return true;
+    } catch {
+      return false;
+    }
+  };
+
+  if (editor === 'vscode') {
+    return commandExists('code');
+  } else if (editor === 'vim') {
+    return commandExists('vim');
+  }
+  return false;
+}
+
+/**
+ * Get the diff command for a specific editor.
+ */
+export function getDiffCommand(
+  oldPath: string,
+  newPath: string,
+  editor: EditorType,
+): DiffCommand | null {
+  switch (editor) {
+    case 'vscode':
+      return {
+        command: 'code',
+        args: ['--wait', '--diff', oldPath, newPath],
+      };
+    case 'vim':
+      return {
+        command: 'vim',
+        args: [
+          '-d',
+          // skip viminfo file to avoid E138 errors
+          '-i',
+          'NONE',
+          // make the left window read-only and the right window editable
+          '-c',
+          'wincmd h | set readonly | wincmd l',
+          // set up colors for diffs
+          '-c',
+          'highlight DiffAdd cterm=bold ctermbg=22 guibg=#005f00 | highlight DiffChange cterm=bold ctermbg=24 guibg=#005f87 | highlight DiffText ctermbg=21 guibg=#0000af | highlight DiffDelete ctermbg=52 guibg=#5f0000',
+          // Show helpful messages
+          '-c',
+          'set showtabline=2 | set tabline=[Instructions]\\ :wqa(save\\ &\\ quit)\\ \\|\\ i/esc(toggle\\ edit\\ mode)',
+          '-c',
+          'wincmd h | setlocal statusline=OLD\\ FILE',
+          '-c',
+          'wincmd l | setlocal statusline=%#StatusBold#NEW\\ FILE\\ :wqa(save\\ &\\ quit)\\ \\|\\ i/esc(toggle\\ edit\\ mode)',
+          // Auto close all windows when one is closed
+          '-c',
+          'autocmd WinClosed * wqa',
+          oldPath,
+          newPath,
+        ],
+      };
+    default:
+      return null;
+  }
+}
+
+/**
+ * Opens a diff tool to compare two files.
+ * Terminal-based editors by default blocks parent process until the editor exits.
+ * GUI-based editors requires args such as "--wait" to block parent process.
+ */
+export async function openDiff(
+  oldPath: string,
+  newPath: string,
+  editor: EditorType,
+): Promise<void> {
+  const diffCommand = getDiffCommand(oldPath, newPath, editor);
+  if (!diffCommand) {
+    console.error('No diff tool available. Install vim or vscode.');
+    return;
+  }
+
+  try {
+    if (editor === 'vscode') {
+      // Use spawn to avoid blocking the entire process, resolve this function when editor is closed.
+      return new Promise((resolve, reject) => {
+        const process = spawn(diffCommand.command, diffCommand.args, {
+          stdio: 'inherit',
+        });
+
+        process.on('close', (code) => {
+          if (code === 0) {
+            resolve();
+          } else {
+            reject(new Error(`VS Code exited with code ${code}`));
+          }
+        });
+
+        process.on('error', (error) => {
+          reject(error);
+        });
+      });
+    } else {
+      // Use execSync for terminal-based editors like vim
+      const command = `${diffCommand.command} ${diffCommand.args.map((arg) => `"${arg}"`).join(' ')}`;
+      execSync(command, {
+        stdio: 'inherit',
+        encoding: 'utf8',
+      });
+    }
+  } catch (error) {
+    console.error(error);
+  }
+}