test(repo): test all packages against their earliest supported rollup versions

.config/vitest.config.mts

@@ -1,9 +1,37 @@
 import { defineConfig } from 'vitest/config';
 import path from 'node:path';
+import { existsSync } from 'node:fs';
+import { fileURLToPath } from 'node:url';
+
+import { getEarliestDependencies } from './vitest.earliest.mts';
 
 const isAutoInstallPackage = path.basename(process.cwd()) === 'auto-install';
+const escapeRegExp = (value: string) => value.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
+
+const getEarliestAliases = (mode: string) =>
+  mode === 'earliest'
+    ? getEarliestDependencies().map(({ name, path: dependencyPath }) => ({
+        find: new RegExp(`^${escapeRegExp(name)}$`),
+        replacement: dependencyPath
+      }))
+    : [];
+
+const getSnapshotPath = (testPath: string, snapExt: string, mode: string) => {
+  const defaultPath = path.join(
+    path.dirname(testPath),
+    'snapshots',
+    path.basename(testPath) + snapExt
+  );
+  // Packages opt in to version-specific snapshots by adding the file to this directory.
+  const earliestPath = path.join(
+    path.dirname(testPath),
+    'snapshots-earliest',
+    path.basename(testPath) + snapExt
+  );
+  return mode === 'earliest' && existsSync(earliestPath) ? earliestPath : defaultPath;
+};
 
-export default defineConfig({
+export default defineConfig(({ mode }) => ({
   test: {
     // Enable global APIs for CommonJS test files.
     globals: true,
@@ -20,16 +48,26 @@ export default defineConfig({
       '**/test/recipes/**',
       '**/test/output/**',
       '**/test/snapshots/**',
+      '**/test/snapshots-earliest/**',
       '**/test/types.ts'
     ],
     // These tests switch process cwd and invoke package managers; run files serially there.
     fileParallelism: !isAutoInstallPackage,
+    // Some tests, e.g. TypeScript-based ones, can take several seconds on slow CI runners.
+    testTimeout: 20000,
     // Keep snapshots in the same location used by Ava.
-    resolveSnapshotPath: (testPath, snapExt) =>
-      path.join(path.dirname(testPath), 'snapshots', path.basename(testPath) + snapExt)
+    resolveSnapshotPath: (testPath, snapExt) => getSnapshotPath(testPath, snapExt, mode),
+    setupFiles:
+      mode === 'earliest'
+        ? [fileURLToPath(new URL('./vitest.setup.earliest.mts', import.meta.url))]
+        : []
   },
   resolve: {
     // Allow importing the current package under test via `~package`
-    alias: [{ find: /^~package$/, replacement: path.resolve(process.cwd()) }]
+    alias: [
+      { find: /^~package$/, replacement: path.resolve(process.cwd()) },
+      // In earliest mode, resolve imports of aliased dependencies to the earliest supported versions.
+      ...getEarliestAliases(mode)
+    ]
   }
-});
+}));

.config/vitest.earliest.mts

@@ -0,0 +1,26 @@
+import { existsSync, readFileSync } from 'node:fs';
+import { join } from 'node:path';
+
+const EARLIEST_SUFFIX = '-earliest';
+
+export function getEarliestDependencies() {
+  const packageJsonPath = join(process.cwd(), 'package.json');
+  const { devDependencies = {} } = JSON.parse(readFileSync(packageJsonPath, 'utf8'));
+  const dependencies = Object.keys(devDependencies)
+    .filter((name) => name.endsWith(EARLIEST_SUFFIX))
+    .map((name) => ({
+      name: name.slice(0, -EARLIEST_SUFFIX.length),
+      path: join(process.cwd(), 'node_modules', name)
+    }));
+  if (!dependencies.some(({ name }) => name === 'rollup')) {
+    throw new Error(`Missing "rollup-earliest" devDependency in ${packageJsonPath}.`);
+  }
+  for (const { path } of dependencies) {
+    if (!existsSync(path)) {
+      throw new Error(
+        `Missing "${path}". Run "pnpm install" to test against the earliest supported versions.`
+      );
+    }
+  }
+  return dependencies;
+}

.config/vitest.setup.earliest.mts

@@ -0,0 +1,35 @@
+// The vite aliases in vitest.config.mts redirect ESM imports of the aliased dependencies to
+// their earliest supported versions, but they do not affect require(...). Patch the Node
+// module resolution so CommonJS tests resolve the same versions.
+import Module from 'node:module';
+
+import { getEarliestDependencies } from './vitest.earliest.mts';
+
+type ResolveFilename = (
+  request: string,
+  parent?: unknown,
+  isMain?: boolean,
+  options?: unknown
+) => string;
+
+const earliestPaths = new Map(
+  getEarliestDependencies().map(({ name, path }) => [name, path] as const)
+);
+
+const originalResolveFilename = (Module as { _resolveFilename?: ResolveFilename })._resolveFilename;
+
+if (
+  originalResolveFilename &&
+  !originalResolveFilename.name.includes('redirectEarliestDependencies')
+) {
+  (Module as { _resolveFilename: ResolveFilename })._resolveFilename =
+    function redirectEarliestDependencies(this: unknown, request, parent, isMain, options) {
+      return originalResolveFilename.call(
+        this,
+        earliestPaths.get(request) ?? request,
+        parent,
+        isMain,
+        options
+      );
+    };
+}

.github/CONTRIBUTING.md

@@ -31,7 +31,7 @@ Any code change should be submitted as a pull request. Our guidelines for Pull R
 Some packages use Vitest for tests. When converting or running tests locally inside a package directory (e.g. `packages/alias`):
 
 - Tests import the package under test via `~package`. A shared config at `.config/vitest.config.mts` provides a runtime alias that resolves `~package` to the current working directory.
-- Snapshots are written alongside each test under a local `.snapshots` directory.
+- Snapshots are written to a `snapshots` directory alongside the tests.
 
 Example (from a package directory):
 
@@ -40,6 +40,8 @@ pnpm build
 pnpm test
 ```
 
+To also run the tests against the earliest version of rollup the package supports, use `pnpm test:earliest`. In this mode, snapshots for a test file are taken from `test/snapshots-earliest` when a file with the same name exists there, falling back to the regular snapshots otherwise. When regenerating snapshots with `-u` in this mode, test files without a counterpart in `test/snapshots-earliest` get their regular snapshots overwritten with the output generated for the earliest rollup version, so when version-specific snapshots are intended, first copy the snapshot file into `test/snapshots-earliest` and then regenerate.
+
 ## Code review process
 
 The bigger the pull request, the longer it will take to review and merge. Try to break down large pull requests in smaller chunks that are easier to review and merge.

.github/workflows/node-windows.yml

@@ -50,3 +50,6 @@ jobs:
 
       - name: run tests
         run: pnpm --workspace-concurrency 1 --filter "...[origin/master]" ci:test
+
+      - name: run tests against earliest supported rollup
+        run: pnpm --workspace-concurrency 1 --filter "...[origin/master]" test:earliest

.github/workflows/validate.yml

@@ -76,3 +76,6 @@ jobs:
 
       - name: Run Tests
         run: pnpm --filter "...[origin/master]" ci:coverage
+
+      - name: Run Tests Against Earliest Supported Rollup
+        run: pnpm --filter "...[origin/master]" test:earliest

.prettierignore

@@ -6,4 +6,5 @@ packages/yaml/test/fixtures/**/*
 **/dist/
 **/fixtures/
 **/snapshots/
+**/snapshots-earliest/
 pnpm-lock.yaml

README.md

@@ -124,6 +124,14 @@ To run tests on a specific package:
 $ pnpm --filter ./packages/<name> test
 ```
 
+To also run the tests of a package against the earliest version of rollup it supports:
+
+```console
+$ pnpm --filter ./packages/<name> test:earliest
+```
+
+In this mode, snapshots are read from the `test/snapshots-earliest` directory of a package when a file with the same name exists there, falling back to the regular snapshots otherwise. Be careful when regenerating snapshots with `-u` in this mode: for test files without a counterpart in `test/snapshots-earliest`, this overwrites the regular snapshots with the output generated for the earliest rollup version. To add version-specific snapshots for a test file, first copy its snapshot file from `test/snapshots` to `test/snapshots-earliest`, then regenerate in this mode.
+
 Linting:
 
 To lint all packages which have changes:

packages/alias/package.json

@@ -32,7 +32,8 @@
     "prerelease": "pnpm build",
     "pretest": "pnpm build",
     "release": "pnpm --workspace-root package:release $(pwd)",
-    "test": "vitest --config ../../.config/vitest.config.mts run"
+    "test": "vitest --config ../../.config/vitest.config.mts run",
+    "test:earliest": "pnpm test -- --mode earliest"
   },
   "files": [
     "dist",
@@ -58,7 +59,8 @@
   "devDependencies": {
     "@rollup/plugin-node-resolve": "^15.0.0",
     "del-cli": "^5.0.0",
-    "rollup": "^4.0.0",
+    "rollup": "catalog:",
+    "rollup-earliest": "npm:rollup@4.0.0",
     "typescript": "catalog:"
   },
   "types": "./dist/index.d.ts",

packages/alias/test/alias.test.ts

@@ -3,14 +3,19 @@ import { fileURLToPath } from 'node:url';
 import os from 'node:os';
 
 import { describe, it, expect } from 'vitest';
-import { rollup } from 'rollup';
+import { rollup, VERSION } from 'rollup';
 import nodeResolvePlugin from '@rollup/plugin-node-resolve';
 
 import alias from '~package';
 
 const DIRNAME = fileURLToPath(new URL('.', import.meta.url));
 const isWindows = os.platform() === 'win32';
 
+// rollup 4.13.0 added a prefix to plugin warning messages
+const [rollupMajor, rollupMinor] = VERSION.split('.').map(Number);
+const warningPrefix =
+  rollupMajor > 4 || (rollupMajor === 4 && rollupMinor >= 13) ? '[plugin alias] ' : '';
+
 /**
  * Helper function to test configuration with Rollup
  * @param plugins is an array of plugins for Rollup, they should include "alias"
@@ -506,9 +511,9 @@ describe('plugin-alias', () => {
     expect(warnList).toMatchObject([
       {
         message:
-          '[plugin alias] rewrote @/warn-importee.js to test/fixtures/folder/warn-importee.js but was not an absolute path and was not handled by other plugins. ' +
-          'This will lead to duplicated modules for the same path. ' +
-          'To avoid duplicating modules, you should resolve to an absolute path.',
+          `${warningPrefix}rewrote @/warn-importee.js to test/fixtures/folder/warn-importee.js but was not an absolute path and was not handled by other plugins. ` +
+          `This will lead to duplicated modules for the same path. ` +
+          `To avoid duplicating modules, you should resolve to an absolute path.`,
         code: 'PLUGIN_WARNING',
         plugin: 'alias'
       }

packages/auto-install/package.json

@@ -35,6 +35,7 @@
     "pretest": "pnpm build",
     "release": "pnpm --workspace-root package:release $(pwd)",
     "test": "vitest --config ../../.config/vitest.config.mts run",
+    "test:earliest": "pnpm test -- --mode earliest",
     "test:ts": "tsc --noEmit"
   },
   "files": [
@@ -63,10 +64,12 @@
   },
   "devDependencies": {
     "@rollup/plugin-node-resolve": "^15.0.0",
+    "@rollup/plugin-node-resolve-earliest": "npm:@rollup/plugin-node-resolve@11.2.1",
     "@rollup/plugin-typescript": "^9.0.1",
     "del": "^6.1.1",
     "node-noop": "^1.0.0",
-    "rollup": "^4.0.0-24",
+    "rollup": "catalog:",
+    "rollup-earliest": "npm:rollup@1.20.0",
     "typescript": "^4.8.3"
   },
   "types": "./types/index.d.ts"

packages/auto-install/test/fixtures/pnpm-bare/.npmrc

@@ -0,0 +1,3 @@
+# pnpm refuses to add dependencies at a workspace root without an explicit opt-in;
+# this also means the root .npmrc no longer applies here, which is fine for this fixture
+ignore-workspace-root-check=true

packages/auto-install/test/fixtures/pnpm-bare/pnpm-workspace.yaml

@@ -0,0 +1,2 @@
+# Anchor pnpm workspace detection to this fixture so that package installs spawned here do not
+# operate on the monorepo workspace root and regenerate its lockfile.

packages/auto-install/test/fixtures/pnpm/.npmrc

@@ -0,0 +1,3 @@
+# pnpm refuses to add dependencies at a workspace root without an explicit opt-in;
+# this also means the root .npmrc no longer applies here, which is fine for this fixture
+ignore-workspace-root-check=true

packages/auto-install/test/fixtures/pnpm/pnpm-workspace.yaml

@@ -0,0 +1,2 @@
+# Anchor pnpm workspace detection to this fixture so that package installs spawned here do not
+# operate on the monorepo workspace root and regenerate its lockfile.

packages/auto-install/test/pnpm-bare.js

@@ -13,6 +13,12 @@ const input = join(cwd, '../input.js');
 
 process.chdir(cwd);
 
+// pnpm would otherwise discover the monorepo workspace root above the fixture and regenerate
+// its lockfile. The fixture pnpm-workspace.yaml anchors workspace detection to the fixture
+// directory; ensure the fixture installs leave the workspace root lockfile untouched.
+const rootLockfile = join(__dirname, '../../../pnpm-lock.yaml');
+const originalLockfileContent = readFileSync(rootLockfile);
+
 test('pnpm, bare', async () => {
   await rollup({
     input,
@@ -28,5 +34,12 @@ test('pnpm, bare', async () => {
 }, 50000);
 
 afterAll(async () => {
-  await del(['node_modules', 'package.json', 'pnpm-lock.yaml']);
+  try {
+    expect(
+      readFileSync(rootLockfile).equals(originalLockfileContent),
+      'the workspace root lockfile was modified by a fixture install'
+    ).toBe(true);
+  } finally {
+    await del(['node_modules', 'package.json', 'pnpm-lock.yaml']);
+  }
 });

packages/auto-install/test/pnpm.js

@@ -13,6 +13,12 @@ const input = join(cwd, '../input.js');
 
 process.chdir(cwd);
 
+// pnpm would otherwise discover the monorepo workspace root above the fixture and regenerate
+// its lockfile. The fixture pnpm-workspace.yaml anchors workspace detection to the fixture
+// directory; ensure the fixture installs leave the workspace root lockfile untouched.
+const rootLockfile = join(__dirname, '../../../pnpm-lock.yaml');
+const originalLockfileContent = readFileSync(rootLockfile);
+
 test('pnpm', async () => {
   await rollup({
     input,
@@ -29,6 +35,13 @@ test('pnpm', async () => {
 }, 50000);
 
 afterAll(async () => {
-  await del(['node_modules', 'package.json']);
-  writeFileSync('pnpm-lock.yaml', '');
+  try {
+    expect(
+      readFileSync(rootLockfile).equals(originalLockfileContent),
+      'the workspace root lockfile was modified by a fixture install'
+    ).toBe(true);
+  } finally {
+    await del(['node_modules', 'package.json']);
+    writeFileSync('pnpm-lock.yaml', '');
+  }
 });

packages/babel/package.json

@@ -35,6 +35,7 @@
     "pretest": "pnpm build",
     "release": "pnpm --workspace-root package:release $(pwd)",
     "test": "vitest --config ../../.config/vitest.config.mts run",
+    "test:earliest": "pnpm test -- --mode earliest",
     "test:ts": "tsc types/index.d.ts test/types.ts --noEmit"
   },
   "files": [
@@ -80,7 +81,8 @@
     "@rollup/plugin-json": "^5.0.0",
     "@rollup/plugin-node-resolve": "^15.0.0",
     "@types/babel__core": "^7.1.9",
-    "rollup": "^4.0.0-24",
+    "rollup": "catalog:",
+    "rollup-earliest": "npm:rollup@2.78.0",
     "source-map": "^0.7.4"
   },
   "types": "./types/index.d.ts",