Fixes settings interpolation with dotenv variables (#5544)

**What's the problem this PR addresses?**

I forgot in #4718 to add a test making sure that the yarnrc settings
could use the variable set in the dotenv files (the existing tests were
mainly around the values set during script execution), and of course I
forgot a change 🥲

**How did you fix it?**

We now pass the updated environment when interpolating values.

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.yarn/versions/a1769d6c.yml

@@ -0,0 +1,2 @@
+declined:
+  - "@yarnpkg/core"

.yarnrc.yml

@@ -13,8 +13,6 @@ enableGlobalCache: false
 immutablePatterns:
   - .pnp.*
 
-initScope: yarnpkg
-
 npmPublishAccess: public
 
 packageExtensions:

packages/acceptance-tests/pkg-tests-specs/sources/features/dotEnvFiles.test.ts

@@ -110,4 +110,20 @@ describe(`DotEnv files`, () => {
 
     await run(`install`);
   }));
+
+  it(`should allow values from environment files to be reused in other configuration settings`, makeTemporaryEnv({}, async ({path, run, source}) => {
+    await run(`install`);
+
+    await xfs.writeFilePromise(ppath.join(path, `.env`), [
+      `INJECTED_FROM_ENV_FILE=hello\n`,
+    ].join(``));
+
+    await xfs.writeJsonPromise(ppath.join(path, Filename.rc), {
+      initScope: `\${INJECTED_FROM_ENV_FILE}`,
+    });
+
+    await expect(run(`config`, `get`, `initScope`)).resolves.toMatchObject({
+      stdout: `hello\n`,
+    });
+  }));
 });

packages/yarnpkg-core/sources/Configuration.ts

@@ -749,7 +749,7 @@ function parseSingleValue(configuration: Configuration, path: string, valueBase:
       throw new Error(`Expected configuration setting "${path}" to be a string, got ${typeof value}`);
 
     const valueWithReplacedVariables = miscUtils.replaceEnvVariables(value, {
-      env: process.env,
+      env: configuration.env,
     });
 
     switch (definition.type) {