fix: Use cmdshim instead of symlink on win32 in base-fetcher

CHANGELOG.md

@@ -16,6 +16,10 @@ Please add one entry in this file for each change in Yarn's behavior. Use the sa
 
   [#6611](https://github.com/yarnpkg/yarn/pull/6611) - [**Jack Zhao**](https://github.com/bugzpodder)
 
+- Fixes an issue with how symlinks are setup into the cache on Windows
+
+  [#6621](https://github.com/yarnpkg/yarn/pull/6621) - [**Yoad Snapir**](https://github.com/yoadsn)
+
 ## 1.12.1
 
 - Ensures the engine check is ran before showing the UI for `upgrade-interactive`

src/constants.js

@@ -28,7 +28,7 @@ export const YARN_INSTALLER_MSI = 'https://yarnpkg.com/latest.msi';
 export const SELF_UPDATE_VERSION_URL = 'https://yarnpkg.com/latest-version';
 
 // cache version, bump whenever we make backwards incompatible changes
-export const CACHE_VERSION = 3;
+export const CACHE_VERSION = 4;
 
 // lockfile version, bump whenever we make backwards incompatible changes
 export const LOCKFILE_VERSION = 1;

src/fetchers/base-fetcher.js

@@ -9,7 +9,9 @@ import normalizeManifest from '../util/normalize-manifest/index.js';
 import {makePortableProxyScript} from '../util/portable-script.js';
 import * as constants from '../constants.js';
 import * as fs from '../util/fs.js';
+import lockMutex from '../util/mutex.js';
 
+const cmdShim = require('@zkochan/cmd-shim');
 const path = require('path');
 
 export default class BaseFetcher {
@@ -77,7 +79,16 @@ export default class BaseFetcher {
           }
 
           await fs.mkdirp(binDest);
-          await fs.symlink(src, `${binDest}/${binName}`);
+          if (process.platform === 'win32') {
+            const unlockMutex = await lockMutex(src);
+            try {
+              await cmdShim.ifExists(src, `${binDest}/${binName}`);
+            } finally {
+              unlockMutex();
+            }
+          } else {
+            await fs.symlink(src, `${binDest}/${binName}`);
+          }
         }
       }