fix(pnp): esm - return undefined source for commonjs

.yarn/versions/d70173f5.yml

@@ -0,0 +1,27 @@
+releases:
+  "@yarnpkg/cli": patch
+  "@yarnpkg/plugin-pnp": patch
+  "@yarnpkg/pnp": patch
+
+declined:
+  - "@yarnpkg/plugin-compat"
+  - "@yarnpkg/plugin-constraints"
+  - "@yarnpkg/plugin-dlx"
+  - "@yarnpkg/plugin-essentials"
+  - "@yarnpkg/plugin-init"
+  - "@yarnpkg/plugin-interactive-tools"
+  - "@yarnpkg/plugin-nm"
+  - "@yarnpkg/plugin-npm-cli"
+  - "@yarnpkg/plugin-pack"
+  - "@yarnpkg/plugin-patch"
+  - "@yarnpkg/plugin-pnpm"
+  - "@yarnpkg/plugin-stage"
+  - "@yarnpkg/plugin-typescript"
+  - "@yarnpkg/plugin-version"
+  - "@yarnpkg/plugin-workspace-tools"
+  - "@yarnpkg/builder"
+  - "@yarnpkg/core"
+  - "@yarnpkg/doctor"
+  - "@yarnpkg/nm"
+  - "@yarnpkg/pnpify"
+  - "@yarnpkg/sdks"

packages/acceptance-tests/pkg-tests-specs/sources/pnp-esm.test.ts

@@ -1004,4 +1004,32 @@ describe(`Plug'n'Play - ESM`, () => {
       ),
     );
   });
+
+  it(
+    `should use the commonjs resolver in commonjs files imported from ESM`,
+    makeTemporaryEnv(
+      {
+        type: `module`,
+      },
+      async ({path, run, source}) => {
+        await xfs.writeFilePromise(ppath.join(path, `foo.js`), `import './bar.cjs';`);
+        await xfs.writeFilePromise(
+          ppath.join(path, `bar.cjs`),
+          `
+          require('module')._extensions['.custom'] = require('module')._extensions['.js'];
+          require('./baz');
+          `,
+        );
+        await xfs.writeFilePromise(ppath.join(path, `baz.custom`), `console.log(42);`);
+
+        await expect(run(`install`)).resolves.toMatchObject({code: 0});
+
+        await expect(run(`node`, `./foo.js`)).resolves.toMatchObject({
+          code: 0,
+          stdout: `42\n`,
+          stderr: ``,
+        });
+      },
+    ),
+  );
 });

packages/yarnpkg-pnp/sources/esm-loader/hooks/load.ts

@@ -15,7 +15,7 @@ export async function load(
     };
   },
   nextLoad: typeof load,
-): Promise<{ format: string, source: string, shortCircuit: boolean }> {
+): Promise<{ format: string, source?: string, shortCircuit: boolean }> {
   const url = loaderUtils.tryParseURL(urlString);
   if (url?.protocol !== `file:`)
     return nextLoad(urlString, context, nextLoad);
@@ -49,7 +49,7 @@ export async function load(
 
   return {
     format,
-    source: await fs.promises.readFile(filePath, `utf8`),
+    source: format === `commonjs` ? undefined : await fs.promises.readFile(filePath, `utf8`),
     shortCircuit: true,
   };
 }