Injects a "process.versions.pnp" variable (#6464)

* Injects a "process.versions.pnp" variable

* Adds a test

CHANGELOG.md

@@ -16,6 +16,10 @@ Please add one entry in this file for each change in Yarn's behavior. Use the sa
 
   [#6449](https://github.com/yarnpkg/yarn/pull/6449) - [**Maël Nison**](https://twitter.com/arcanis)
 
+- Makes the PnP hook inject a `process.versions.pnp` variable when setup (equals to `VERSIONS.std`)
+
+  [#6464](https://github.com/yarnpkg/yarn/pull/6464) - [**Maël Nison**](https://twitter.com/arcanis)
+
 - Fixes the display name of the faulty package when the NPM registry returns corrupted data
 
   [#6455](https://github.com/yarnpkg/yarn/pull/6455) - [**Grey Baker**](https://github.com/greysteil)

packages/pkg-tests/pkg-tests-specs/sources/pnp.js

@@ -523,7 +523,7 @@ module.exports = makeTemporaryEnv => {
     test(
       `it should export the PnP API through the 'pnpapi' name`,
       makeTemporaryEnv(
-        {dependencies: {[`no-deps`]: `1.0.0`}},
+        {},
         {
           plugNPlay: true,
         },
@@ -535,6 +535,19 @@ module.exports = makeTemporaryEnv => {
       ),
     );
 
+    test(
+      `it should expose the PnP version through 'process.versions.pnp'`,
+      makeTemporaryEnv({}, {plugNPlay: true}, async ({path, run, source}) => {
+        await run(`install`);
+
+        const pnpapiVersionsStd = await source(`require('pnpapi').VERSIONS.std`);
+        const processVersionsPnp = await source(`process.versions.pnp`);
+
+        await expect(typeof processVersionsPnp).toEqual(`string`);
+        await expect(processVersionsPnp).toEqual(String(pnpapiVersionsStd));
+      }),
+    );
+
     test(
       `it should not update the installConfig.pnp field of the package.json when installing with an environment override`,
       makeTemporaryEnv(

src/util/generate-pnp-map-api.tpl.js

@@ -677,6 +677,8 @@ exports.setup = function setup() {
 
     return false;
   };
+
+  process.versions.pnp = String(exports.VERSIONS.std);
 };
 
 exports.setupCompatibilityLayer = () => {