Add @types packages support (#360)

CHANGELOG.md

@@ -17,7 +17,15 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 <!-- ### Fixed -->
 <!-- ### Removed -->
 
-<!-- ## Unreleased -->
+## Unreleased
+
+### Added
+
+- Fetch all `@types` packages listed in the project's `package.json` file and
+  include them for TypeScript compilation. This allows type-checking packages
+  that do not ship their own types but do have a DefinitelyTyped package
+  available. Note: This does not automatically download the `@types` package for
+  a package. It must be manually listed in `package.json`.
 
 ## [0.17.0] - 2022-11-11
 

README.md

@@ -361,6 +361,10 @@ statement should use the `.js` extension (the same as you would do when running
 import './my-other-module.js';
 ```
 
+You may also include any Definitely Typed (`@types`) packages for type checking
+during compilation by listing it as a dependency in the project's
+[`package.json` file](#packagejson).
+
 ## Hiding & folding
 
 If a region of code in a Playground project file is surrounded by

src/test/types-fetcher_test.ts

@@ -630,6 +630,52 @@ suite('types fetcher', () => {
     });
   });
 
+  test('@types package', async () => {
+    const sourceTexts: string[] = [];
+    const packageJson: PackageJson = {
+      dependencies: {
+        '@types/a': '1.0.0',
+      },
+    };
+    const cdnData: CdnData = {
+      '@types/a': {
+        versions: {
+          '1.0.0': {
+            files: {
+              'index.d.ts': {
+                content: 'declare module a { export const a: 1; }',
+              },
+            },
+          },
+        },
+      },
+    };
+    const expectedDependencyGraph: ExpectedDependencyGraph = {
+      root: {
+        '@types/a': '1.0.0',
+      },
+      deps: {},
+    };
+    const expectedLayout: NodeModulesDirectory = {
+      '@types/a': {
+        version: '1.0.0',
+        nodeModules: {},
+      },
+    };
+    const expectedFiles = new Map([
+      ['@types/a/index.d.ts', 'declare module a { export const a: 1; }'],
+      ['@types/a/package.json', '{}'],
+    ]);
+    await checkTypesFetcher({
+      sourceTexts,
+      packageJson,
+      cdnData,
+      expectedFiles,
+      expectedDependencyGraph,
+      expectedLayout,
+    });
+  });
+
   test('declare module', async () => {
     // Declaring a module should not count as an import, but anything imported
     // from within the declare module block should.

src/typescript-worker/types-fetcher.ts

@@ -94,6 +94,7 @@ export class TypesFetcher {
         fetcher._handleBareAndRelativeSpecifiers(source, root)
       ),
       ...tsLibs.map((lib) => fetcher._addTypeScriptStandardLib(lib)),
+      fetcher._fetchTypesPackages(),
     ]);
     const layout = new NodeModulesLayoutMaker().layout(
       fetcher._rootDependencies,
@@ -123,6 +124,27 @@ export class TypesFetcher {
     this._rootPackageJson = rootPackageJson;
   }
 
+  private async _fetchTypesPackages(): Promise<void> {
+    if (
+      this._rootPackageJson === undefined ||
+      this._rootPackageJson.dependencies === undefined
+    ) {
+      return;
+    }
+
+    const typesPackages = Object.keys(
+      this._rootPackageJson.dependencies
+    ).filter((k) => k.startsWith('@types/'));
+
+    if (typesPackages.length === 0) {
+      return;
+    }
+
+    await Promise.allSettled(
+      typesPackages.map((k) => this._handleBareSpecifier(k, root))
+    );
+  }
+
   private async _addTypeScriptStandardLib(lib: string): Promise<void> {
     return this._handleBareSpecifier(
       `typescript/lib/lib.${lib.toLowerCase()}.js`,

web-test-runner.config.js

@@ -45,8 +45,9 @@ export default {
     // only one or the other can be installed at once (see our "postinstall" NPM
     // script). See
     // https://modern-web.dev/docs/test-runner/browser-launchers/puppeteer/.
-    puppeteerLauncher({launchOptions: {product: 'firefox'}}),
+    puppeteerLauncher({launchOptions: {product: 'firefox'}, concurrency: 1}),
   ],
+  concurrentBrowsers: Number(process.env.CONCURRENT_BROWSERS) || 2, // default 2
   browserStartTimeout: 30000, // default 30000
   testsStartTimeout: 20000, // default 10000
   testsFinishTimeout: 90000, // default 20000