Fixes importing the PnP API from ESM modules

Author: arcanis

.pnp.loader.mjs

@@ -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"

.yarn/versions/fb5469c7.yml

@@ -46,6 +46,28 @@ describe(`Plug'n'Play - ESM`, () => {
     ),
   );
 
+  test(
+    `it should be able to import the PnP API`,
+    makeTemporaryEnv(
+      {
+        type: `module`,
+      },
+      async ({path, run, source}) => {
+        await expect(run(`install`)).resolves.toMatchObject({code: 0});
+
+        await xfs.writeFilePromise(
+          ppath.join(path, `index.js` as Filename),
+          `import pnp from 'pnpapi';\nconsole.log(typeof pnp.resolveRequest)`,
+        );
+
+        await expect(run(`node`, `./index.js`)).resolves.toMatchObject({
+          code: 0,
+          stdout: `function\n`,
+        });
+      },
+    ),
+  );
+
   test(
     `it should be able to import a dependency`,
     makeTemporaryEnv(

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

@@ -88,7 +88,7 @@ export async function resolve(
 
     // If the package.json doesn't list an `exports` field, Node will tolerate omitting the extension
     // https://github.com/nodejs/node/blob/0996eb71edbd47d9f9ec6153331255993fd6f0d1/lib/internal/modules/esm/resolve.js#L686-L691
-    if (subPath === ``) {
+    if (subPath === `` && dependencyName !== `pnpapi`) {
       const resolved = pnpapi.resolveToUnqualified(`${dependencyName}/package.json`, issuer);
       if (resolved) {
         const content = await loaderUtils.tryReadFile(resolved);