fix(migrate): limit automatic formatting to changed files

Author: fengmk2

docs/guide/migrate-rules.md

@@ -220,6 +220,8 @@ Unrelated `bunx` commands and other package-executor forms remain unchanged.
 After updating the manifests and package-manager configuration, migration
 reinstalls dependencies once to refresh the lockfile. If installation fails,
 migration reports the error and exits with a nonzero status. After a successful
-migration, it runs `vp fmt` unless the project still uses Prettier. A formatter
-failure is reported as a warning so the migration result and manual formatting
-command remain available.
+migration, it runs `vp fmt` on supported files changed in the Git worktree,
+leaving unrelated project files untouched. Non-Git projects retain full-project
+formatting. Formatting is skipped while the project still uses Prettier. A
+formatter failure is reported as a warning so the migration result and manual
+formatting command remain available.

packages/cli/snap-tests-global/migration-eslint-npx-wrapper/snap.txt

@@ -1,18 +1,18 @@
-> vp migrate --no-interactive # migration should rewrite bare eslint but leave npx wrappers unchanged
+> vp migrate --no-interactive # migration should rewrite bare and bunx eslint but leave other wrappers unchanged
 ◇ Migrated . to Vite+
 • Node <semver>  pnpm <semver>
 • 4 config updates applied
 • ESLint rules migrated to Oxlint
 
-> cat package.json # check eslint removed, bare eslint rewritten, npx/pnpm exec/bunx wrappers unchanged
+> cat package.json # check eslint removed, bare and bunx eslint rewritten, npx/pnpm exec unchanged
 {
   "name": "migration-eslint-npx-wrapper",
   "scripts": {
     "dev": "vp dev",
     "build": "vp build",
     "lint": "npx eslint .",
     "lint:fix": "pnpm exec eslint --fix .",
-    "lint:bunx": "bunx eslint .",
+    "lint:bunx": "bunx vp lint .",
     "lint:bare": "vp lint --fix .",
     "prepare": "vp config"
   },

packages/cli/snap-tests-global/migration-eslint-npx-wrapper/steps.json

@@ -1,7 +1,7 @@
 {
   "commands": [
-    "vp migrate --no-interactive # migration should rewrite bare eslint but leave npx wrappers unchanged",
-    "cat package.json # check eslint removed, bare eslint rewritten, npx/pnpm exec/bunx wrappers unchanged",
+    "vp migrate --no-interactive # migration should rewrite bare and bunx eslint but leave other wrappers unchanged",
+    "cat package.json # check eslint removed, bare and bunx eslint rewritten, npx/pnpm exec unchanged",
     "cat pnpm-workspace.yaml # check pnpm-workspace.yaml has overrides and catalog",
     "test ! -f eslint.config.mjs # check eslint config is removed"
   ]

packages/cli/snap-tests-global/new-vite-monorepo-bun/snap.txt

@@ -3,7 +3,6 @@
 AGENTS.md
 README.md
 apps
-bunfig.toml
 package.json
 packages
 tsconfig.json

packages/cli/src/migration/__tests__/format.spec.ts

@@ -1,6 +1,11 @@
+import { execFileSync } from 'node:child_process';
+import fs from 'node:fs';
+import os from 'node:os';
+import path from 'node:path';
+
 import { describe, expect, it, vi } from 'vitest';
 
-import { canFormatWithOxfmt, formatMigratedProject } from '../format.ts';
+import { canFormatWithOxfmt, collectChangedFormatPaths, formatMigratedProject } from '../format.ts';
 import { createMigrationReport } from '../report.ts';
 
 describe('formatMigratedProject', () => {
@@ -11,16 +16,31 @@ describe('formatMigratedProject', () => {
       status: 'formatted',
     });
     const report = createMigrationReport();
+    const collectPaths = vi.fn().mockResolvedValue(['package.json', 'vite.config.ts']);
 
-    await expect(formatMigratedProject('/project', false, report, format)).resolves.toBe(true);
-    expect(format).toHaveBeenCalledWith('/project', false, undefined, {
+    await expect(
+      formatMigratedProject('/project', false, report, format, collectPaths),
+    ).resolves.toBe(true);
+    expect(format).toHaveBeenCalledWith('/project', false, ['package.json', 'vite.config.ts'], {
       silent: false,
       command: process.execPath,
       commandArgs: [...process.execArgv, process.argv[1]],
     });
     expect(report.warnings).toEqual([]);
   });
 
+  it('skips formatting when migration changed no supported files', async () => {
+    const format = vi.fn();
+    const report = createMigrationReport();
+    const collectPaths = vi.fn().mockResolvedValue([]);
+
+    await expect(
+      formatMigratedProject('/project', false, report, format, collectPaths),
+    ).resolves.toBe(true);
+    expect(format).not.toHaveBeenCalled();
+    expect(report.warnings).toEqual([]);
+  });
+
   it('reports a formatter nonzero exit without throwing', async () => {
     const format = vi.fn().mockResolvedValue({
       durationMs: 1,
@@ -46,6 +66,37 @@ describe('formatMigratedProject', () => {
   });
 });
 
+describe('collectChangedFormatPaths', () => {
+  it('collects supported changed Git paths without formatting unrelated files', async () => {
+    const projectRoot = fs.mkdtempSync(path.join(os.tmpdir(), 'vp-migrate-format-'));
+    try {
+      execFileSync('git', ['init'], { cwd: projectRoot, stdio: 'ignore' });
+      fs.writeFileSync(path.join(projectRoot, 'package.json'), '{}\n');
+      fs.writeFileSync(path.join(projectRoot, 'vite.config.ts'), 'export default {}\n');
+      fs.writeFileSync(path.join(projectRoot, 'template.mdx'), '# untouched\n');
+      fs.writeFileSync(path.join(projectRoot, 'bun.lock'), 'lockfileVersion = 1\n');
+      execFileSync('git', ['add', 'package.json'], { cwd: projectRoot });
+      fs.appendFileSync(path.join(projectRoot, 'package.json'), '\n');
+
+      await expect(collectChangedFormatPaths(projectRoot)).resolves.toEqual([
+        'package.json',
+        'vite.config.ts',
+      ]);
+    } finally {
+      fs.rmSync(projectRoot, { recursive: true, force: true });
+    }
+  });
+
+  it('falls back to full-project formatting outside Git', async () => {
+    const projectRoot = fs.mkdtempSync(path.join(os.tmpdir(), 'vp-migrate-format-no-git-'));
+    try {
+      await expect(collectChangedFormatPaths(projectRoot)).resolves.toBeUndefined();
+    } finally {
+      fs.rmSync(projectRoot, { recursive: true, force: true });
+    }
+  });
+});
+
 describe('canFormatWithOxfmt', () => {
   it('formats projects that do not use Prettier', () => {
     expect(canFormatWithOxfmt(false, false)).toBe(true);

packages/cli/src/migration/format.ts

@@ -1,3 +1,7 @@
+import fs from 'node:fs';
+import path from 'node:path';
+
+import { runCommandSilently } from '../utils/command.ts';
 import { type CommandRunSummary, runViteFmt } from '../utils/prompts.ts';
 import { addMigrationWarning, type MigrationReport } from './report.ts';
 
@@ -8,9 +12,94 @@ type FormatRunner = (
   options?: { silent?: boolean; command?: string; commandArgs?: string[] },
 ) => Promise<CommandRunSummary>;
 
+type FormatPathCollector = (cwd: string) => Promise<string[] | undefined>;
+
 const FORMAT_FAILURE_MESSAGE =
   'Automatic formatting failed. Run `vp fmt` manually after migration.';
 
+const FORMAT_EXTENSIONS = new Set([
+  '.astro',
+  '.cjs',
+  '.css',
+  '.cts',
+  '.html',
+  '.js',
+  '.json',
+  '.jsonc',
+  '.jsx',
+  '.less',
+  '.md',
+  '.mjs',
+  '.mts',
+  '.scss',
+  '.svelte',
+  '.toml',
+  '.ts',
+  '.tsx',
+  '.vue',
+  '.yaml',
+  '.yml',
+]);
+
+function parseNullDelimitedPaths(output: Buffer): string[] {
+  return output.toString().split('\0').filter(Boolean);
+}
+
+function isFormatCandidate(projectRoot: string, relativePath: string): boolean {
+  const absolutePath = path.join(projectRoot, relativePath);
+  return (
+    fs.existsSync(absolutePath) &&
+    fs.statSync(absolutePath).isFile() &&
+    FORMAT_EXTENSIONS.has(path.extname(relativePath).toLowerCase())
+  );
+}
+
+/**
+ * Limit automatic formatting to files changed in the current Git worktree.
+ * This prevents migration from reformatting unrelated source trees while still
+ * covering manifests, generated config, and rewritten imports.
+ *
+ * Return `undefined` outside a Git worktree so non-Git projects retain the
+ * existing full-project formatting behavior.
+ */
+export async function collectChangedFormatPaths(
+  projectRoot: string,
+): Promise<string[] | undefined> {
+  try {
+    const git = (args: string[]) =>
+      runCommandSilently({ command: 'git', args, cwd: projectRoot, envs: process.env });
+    const [unstaged, staged, untracked] = await Promise.all([
+      git(['diff', '--name-only', '--relative', '-z', '--diff-filter=ACMRTUXB', '--', '.']),
+      git([
+        'diff',
+        '--cached',
+        '--name-only',
+        '--relative',
+        '-z',
+        '--diff-filter=ACMRTUXB',
+        '--',
+        '.',
+      ]),
+      git(['ls-files', '--others', '--exclude-standard', '-z', '--', '.']),
+    ]);
+    if (unstaged.exitCode !== 0 || staged.exitCode !== 0 || untracked.exitCode !== 0) {
+      return undefined;
+    }
+
+    return [
+      ...new Set([
+        ...parseNullDelimitedPaths(unstaged.stdout),
+        ...parseNullDelimitedPaths(staged.stdout),
+        ...parseNullDelimitedPaths(untracked.stdout),
+      ]),
+    ]
+      .filter((file) => isFormatCandidate(projectRoot, file))
+      .toSorted();
+  } catch {
+    return undefined;
+  }
+}
+
 /**
  * Do not apply Oxfmt to a project that still uses Prettier. Their formatting
  * rules can conflict, especially when Prettier is enforced through ESLint.
@@ -33,10 +122,15 @@ export async function formatMigratedProject(
   interactive: boolean,
   report: MigrationReport,
   format: FormatRunner = runViteFmt,
+  collectPaths: FormatPathCollector = collectChangedFormatPaths,
 ): Promise<boolean> {
   try {
+    const paths = await collectPaths(projectRoot);
+    if (paths?.length === 0) {
+      return true;
+    }
     const cliEntry = process.argv[1];
-    const result = await format(projectRoot, interactive, undefined, {
+    const result = await format(projectRoot, interactive, paths, {
       silent: false,
       ...(cliEntry
         ? { command: process.execPath, commandArgs: [...process.execArgv, cliEntry] }

rfcs/migration-command.md

@@ -581,6 +581,14 @@ migrations run. Nested launcher forms such as
 `portless --tailscale run bunx --bun vite` are also handled. Other package
 executors remain unchanged and can be addressed separately.
 
+## Post-Migration Formatting
+
+After a successful install, migration runs the formatter only on supported
+files changed in the Git worktree. This formats manifests, generated config,
+and rewritten source without reformatting unrelated files in a large project.
+Non-Git projects retain full-project formatting. Projects that still use
+Prettier are not formatted automatically.
+
 ## ESLint Migration
 
 When an ESLint flat config (`eslint.config.{js,mjs,cjs,ts,mts,cts}`) and `eslint` dependency are detected, `vp migrate` offers to convert the ESLint configuration to oxlint using [`@oxlint/migrate`](https://www.npmjs.com/package/@oxlint/migrate).