feat(migrate): add warnings if certain packages and config files are found

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

@@ -0,0 +1,80 @@
+import fs from 'node:fs';
+import os from 'node:os';
+import path from 'node:path';
+
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+
+import { detectMigrationWarnings } from '../detector.ts';
+
+function writeProject(projectPath: string, packageJson: object, configFiles: string[] = []): void {
+  fs.mkdirSync(projectPath, { recursive: true });
+  fs.writeFileSync(path.join(projectPath, 'package.json'), JSON.stringify(packageJson));
+  for (const configFile of configFiles) {
+    fs.writeFileSync(path.join(projectPath, configFile), '');
+  }
+}
+
+describe('detectMigrationWarnings', () => {
+  let tmpDir: string;
+
+  beforeEach(() => {
+    tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'vp-migration-detector-'));
+  });
+
+  afterEach(() => {
+    fs.rmSync(tmpDir, { recursive: true, force: true });
+  });
+
+  it('detects matching packages and config file variants', () => {
+    writeProject(
+      tmpDir,
+      {
+        devDependencies: { rollup: '^4.0.0', jest: '^30.0.0' },
+        dependencies: { rolldown: '^1.0.0' },
+      },
+      ['rollup.config.mjs', 'rolldown.config.cjs', 'jest.config.json'],
+    );
+
+    expect(detectMigrationWarnings(tmpDir)).toEqual([
+      'Rollup configuration detected. Rollup is API-compatible with Rolldown and can be migrated first before migrating further to tsdown or Vite. Once migrated to tsdown or Vite, re-run vp migrate.',
+      'Rolldown configuration detected. Rolldown can be migrated to tsdown or Vite, and it is recommended to do so. Once migrated, re-run vp migrate.',
+      'Jest configuration detected. Vitest is highly compatible with Jest, and so we recommend migrating. See the Vitest Jest migration guide: https://vitest.dev/guide/migration/jest, then re-run vp migrate.',
+    ]);
+  });
+
+  it('does not warn when the package and config are not both present', () => {
+    writeProject(tmpDir, { devDependencies: { rollup: '^4.0.0' } }, ['jest.config.ts']);
+
+    expect(detectMigrationWarnings(tmpDir)).toEqual([]);
+  });
+
+  it('detects Jest configuration in package.json', () => {
+    writeProject(tmpDir, {
+      devDependencies: { jest: '^30.0.0' },
+      jest: { testEnvironment: 'node' },
+    });
+
+    expect(detectMigrationWarnings(tmpDir)).toEqual([
+      'Jest configuration detected. Vitest is highly compatible with Jest, and so we recommend migrating. See the Vitest Jest migration guide: https://vitest.dev/guide/migration/jest, then re-run vp migrate.',
+    ]);
+  });
+
+  it('detects matching packages and configs in workspace packages', () => {
+    writeProject(path.join(tmpDir, 'packages/app'), { dependencies: { jest: '^30.0.0' } }, [
+      'jest.config.ts',
+    ]);
+
+    expect(detectMigrationWarnings(tmpDir, [{ name: 'app', path: 'packages/app' }])).toEqual([
+      'Jest configuration detected. Vitest is highly compatible with Jest, and so we recommend migrating. See the Vitest Jest migration guide: https://vitest.dev/guide/migration/jest, then re-run vp migrate.',
+    ]);
+  });
+
+  it('detects workspace configs with dependencies declared at the root', () => {
+    writeProject(tmpDir, { devDependencies: { jest: '^30.0.0' } });
+    writeProject(path.join(tmpDir, 'packages/app'), {}, ['jest.config.js']);
+
+    expect(detectMigrationWarnings(tmpDir, [{ name: 'app', path: 'packages/app' }])).toEqual([
+      'Jest configuration detected. Vitest is highly compatible with Jest, and so we recommend migrating. See the Vitest Jest migration guide: https://vitest.dev/guide/migration/jest, then re-run vp migrate.',
+    ]);
+  });
+});

packages/cli/src/migration/bin.ts

@@ -39,6 +39,7 @@ import {
 import type { PackageDependencies } from '../utils/types.ts';
 import { detectWorkspace } from '../utils/workspace.ts';
 import { checkRolldownCompatibility } from './compat/runner.ts';
+import { detectMigrationWarnings } from './detector.ts';
 import { canFormatWithOxfmt, collectChangedFormatPaths, formatMigratedProject } from './format.ts';
 import { handleInstallResult } from './install-result.ts';
 import {
@@ -614,12 +615,7 @@ function showMigrationSummary(options: {
   if (suggestFullMigration) {
     log(FULL_MIGRATION_HINT);
   }
-  if (report.warnings.length > 0) {
-    log(`${styleText('yellow', '!')} Warnings:`);
-    for (const warning of report.warnings) {
-      log(`  - ${warning}`);
-    }
-  }
+  showMigrationWarnings(report.warnings);
   if (report.manualSteps.length > 0) {
     log(`${styleText('blue', '→')} Manual follow-up:`);
     for (const step of report.manualSteps) {
@@ -628,6 +624,16 @@ function showMigrationSummary(options: {
   }
 }
 
+function showMigrationWarnings(warnings: readonly string[]): void {
+  if (warnings.length === 0) {
+    return;
+  }
+  log(`${styleText('yellow', '!')} Warnings:`);
+  for (const warning of warnings) {
+    log(`  - ${warning}`);
+  }
+}
+
 async function downloadSupportedPackageManager(options: {
   rootDir: string;
   packageManager: PackageManager;
@@ -718,6 +724,9 @@ async function executeMigrationPlan(
   report: MigrationReport;
 }> {
   const report = createMigrationReport();
+  report.warnings.push(
+    ...detectMigrationWarnings(workspaceInfoOptional.rootDir, workspaceInfoOptional.packages),
+  );
   const migrationProgress = interactive ? prompts.spinner({ indicator: 'timer' }) : undefined;
   let migrationProgressStarted = false;
   const updateMigrationProgress = (message: string) => {
@@ -1062,6 +1071,10 @@ async function main() {
     let finalInstallOk = true;
     let canFormatMigratedProject = !process.env.VP_SKIP_INSTALL;
     const report = createMigrationReport();
+    // Only --full opts existing projects into tool migration advice.
+    const migrationWarnings = options.full
+      ? detectMigrationWarnings(workspaceInfoOptional.rootDir, workspaceInfoOptional.packages)
+      : [];
     // Report reviews at the end with updated locations. Keep them out of the
     // report until then so review-only items do not force an up-to-date project
     // through dependency reconciliation on every run.
@@ -1227,6 +1240,7 @@ async function main() {
         ? hasExistingVitePlusMigrationCandidates(workspaceInfoOptional, options)
         : hasExplicitExistingVitePlusSetupRequest(options))
     ) {
+      showMigrationWarnings(migrationWarnings);
       if (vitestV5Preflight) {
         prompts.log.warn(vitestV5Preflight);
       }
@@ -1239,6 +1253,7 @@ async function main() {
       prompts.outro(`This project is already using Vite+! ${accent('Happy coding!')}`);
       return;
     }
+    report.warnings.push(...migrationWarnings);
     for (const warning of coreMigrationResult.taskCacheWarnings) {
       addMigrationWarning(report, warning);
     }

packages/cli/src/migration/detector.ts

@@ -1,6 +1,7 @@
 import fs from 'node:fs';
 import path from 'node:path';
 
+import type { WorkspacePackage } from '../types/index.ts';
 import { VITE_CONFIG_FILES } from '../utils/constants.ts';
 
 export interface ConfigFiles {
@@ -59,6 +60,93 @@ export const PRETTIER_CONFIG_FILES = [
   'prettier.config.mts',
 ] as const;
 
+const CONFIG_SCRIPT_EXTENSIONS = ['js', 'mjs', 'cjs', 'ts', 'mts', 'cts'] as const;
+
+const MIGRATION_WARNING_DETECTIONS = [
+  {
+    packageName: 'rollup',
+    configFiles: CONFIG_SCRIPT_EXTENSIONS.map((extension) => `rollup.config.${extension}`),
+    warning:
+      'Rollup configuration detected. Rollup is API-compatible with Rolldown and can be migrated first before migrating further to tsdown or Vite. Once migrated to tsdown or Vite, re-run vp migrate.',
+  },
+  {
+    packageName: 'rolldown',
+    configFiles: CONFIG_SCRIPT_EXTENSIONS.map((extension) => `rolldown.config.${extension}`),
+    warning:
+      'Rolldown configuration detected. Rolldown can be migrated to tsdown or Vite, and it is recommended to do so. Once migrated, re-run vp migrate.',
+  },
+  {
+    packageName: 'jest',
+    configFiles: [
+      ...CONFIG_SCRIPT_EXTENSIONS.map((extension) => `jest.config.${extension}`),
+      'jest.config.json',
+    ],
+    packageJsonField: 'jest',
+    warning:
+      'Jest configuration detected. Vitest is highly compatible with Jest, and so we recommend migrating. See the Vitest Jest migration guide: https://vitest.dev/guide/migration/jest, then re-run vp migrate.',
+  },
+] as const;
+
+function hasDependency(packageJson: Record<string, unknown>, packageName: string): boolean {
+  return ['dependencies', 'devDependencies', 'optionalDependencies'].some((field) => {
+    const dependencies = packageJson[field];
+    return typeof dependencies === 'object' && dependencies !== null && packageName in dependencies;
+  });
+}
+
+/**
+ * Detect tools that have a direct migration path worth showing before the
+ * regular Vite+ migration steps run.
+ */
+export function detectMigrationWarnings(
+  projectPath: string,
+  packages: readonly WorkspacePackage[] = [],
+): string[] {
+  const projectPaths = [
+    projectPath,
+    ...packages.map((workspacePackage) => path.join(projectPath, workspacePackage.path)),
+  ];
+  const detected = new Set<string>();
+  let rootPackageJson: Record<string, unknown> | undefined;
+
+  for (const currentPath of projectPaths) {
+    const packageJsonPath = path.join(currentPath, 'package.json');
+    if (!fs.existsSync(packageJsonPath)) {
+      continue;
+    }
+
+    let packageJson: Record<string, unknown>;
+    try {
+      packageJson = JSON.parse(fs.readFileSync(packageJsonPath, 'utf8')) as Record<string, unknown>;
+    } catch {
+      continue;
+    }
+    if (currentPath === projectPath) {
+      rootPackageJson = packageJson;
+    }
+
+    for (const detection of MIGRATION_WARNING_DETECTIONS) {
+      if (
+        (hasDependency(packageJson, detection.packageName) ||
+          (currentPath !== projectPath &&
+            rootPackageJson !== undefined &&
+            hasDependency(rootPackageJson, detection.packageName))) &&
+        (detection.configFiles.some((configFile) =>
+          fs.existsSync(path.join(currentPath, configFile)),
+        ) ||
+          ('packageJsonField' in detection &&
+            Object.hasOwn(packageJson, detection.packageJsonField)))
+      ) {
+        detected.add(detection.warning);
+      }
+    }
+  }
+
+  return MIGRATION_WARNING_DETECTIONS.map(({ warning }) => warning).filter((warning) =>
+    detected.has(warning),
+  );
+}
+
 export function detectConfigs(projectPath: string): ConfigFiles {
   const configs: ConfigFiles = {};