fix(#1027): Improve yarn v4+ corepack support with better error handling

This change improves the action's handling of yarn v4+ which requires corepack.

Changes:
- Add enableCorepackIfSupported() helper function to automatically enable corepack
- Update yarn getCacheFolderPath to call corepack enable before checking yarn version
- Detect corepack-related errors and provide clear, actionable error messages
- Users can either enable corepack before the action or disable caching

The error message now clearly explains:
- The requirement for corepack with yarn v4+
- How to enable corepack: 'corepack enable'
- Alternative: disable caching with 'package-manager-cache: false'
- Link to GitHub issue for more context

Fixes #1027
Related: https://github.com/actions/setup-node/issues/1027

src/cache-utils.ts

@@ -40,11 +40,32 @@ export const supportedPackageManagers: SupportedPackageManagers = {
     name: 'yarn',
     lockFilePatterns: ['yarn.lock'],
     getCacheFolderPath: async projectDir => {
-      const yarnVersion = await getCommandOutputNotEmpty(
-        `yarn --version`,
-        'Could not retrieve version of yarn',
-        projectDir
-      );
+      // Try to enable corepack first if available
+      // This helps with yarn v2+ which requires corepack
+      await enableCorepackIfSupported();
+
+      let yarnVersion: string;
+      try {
+        yarnVersion = await getCommandOutputNotEmpty(
+          `yarn --version`,
+          'Could not retrieve version of yarn',
+          projectDir
+        );
+      } catch (err) {
+        // Check if this is a corepack error message
+        const errorMsg = (err as Error).message;
+        if (
+          errorMsg.includes('packageManager') &&
+          errorMsg.includes('Corepack')
+        ) {
+          throw new Error(
+            `Yarn v4+ requires corepack to be enabled. Please run 'corepack enable' before using ` +
+              `actions/setup-node with yarn, or disable caching with 'package-manager-cache: false'. ` +
+              `See: https://github.com/actions/setup-node/issues/1027 for more information.`
+          );
+        }
+        throw err;
+      }
 
       core.debug(
         `Consumed yarn version is ${yarnVersion} (working dir: "${
@@ -66,6 +87,24 @@ export const supportedPackageManagers: SupportedPackageManagers = {
   }
 };
 
+/**
+ * Tries to enable corepack for Node.js versions that support it (16.9+)
+ * This helps with yarn v2+ which requires corepack
+ * See: https://github.com/actions/setup-node/issues/1027
+ */
+const enableCorepackIfSupported = async (): Promise<void> => {
+  try {
+    await exec.exec('corepack', ['enable'], {
+      ignoreReturnCode: true,
+      silent: true
+    });
+    core.debug('Corepack enabled successfully');
+  } catch {
+    // Corepack not available or failed silently
+    core.debug('Corepack not available on this system');
+  }
+};
+
 export const getCommandOutput = async (
   toolCommand: string,
   cwd?: string