feat: Adds guard to avoid stepping on Yarn's feet (#714)

* feat: Adds guard to avoid stepping on Yarn's feet

* Makes the path more specific

* Apply feedback

* Fixes test

Author: arcanis

sources/commands/Disable.ts

@@ -3,6 +3,7 @@ import fs                                                                from 'f
 import path                                                              from 'path';
 import which                                                             from 'which';
 
+import * as corepackUtils                                                from '../corepackUtils';
 import {Context}                                                         from '../main';
 import type {NodeError}                                                  from '../nodeUtils';
 import {isSupportedPackageManager, SupportedPackageManagerSetWithoutNpm} from '../types';
@@ -70,6 +71,11 @@ export class DisableCommand extends Command<Context> {
   async removePosixLink(installDirectory: string, binName: string) {
     const file = path.join(installDirectory, binName);
     try {
+      if (binName.includes(`yarn`) && corepackUtils.isYarnSwitchPath(await fs.promises.realpath(file))) {
+        console.warn(`${binName} is already installed in ${file} and points to a Yarn Switch install - skipping`);
+        return;
+      }
+
       await fs.promises.unlink(file);
     } catch (err) {
       if ((err as NodeError).code !== `ENOENT`) {

sources/commands/Enable.ts

@@ -4,6 +4,7 @@ import fs                                                                from 'f
 import path                                                              from 'path';
 import which                                                             from 'which';
 
+import * as corepackUtils                                                from '../corepackUtils';
 import {Context}                                                         from '../main';
 import {isSupportedPackageManager, SupportedPackageManagerSetWithoutNpm} from '../types';
 
@@ -83,6 +84,12 @@ export class EnableCommand extends Command<Context> {
 
     if (fs.existsSync(file)) {
       const currentSymlink = await fs.promises.readlink(file);
+
+      if (binName.includes(`yarn`) && corepackUtils.isYarnSwitchPath(await fs.promises.realpath(file))) {
+        console.warn(`${binName} is already installed in ${file} and points to a Yarn Switch install - skipping`);
+        return;
+      }
+
       if (currentSymlink !== symlink) {
         await fs.promises.unlink(file);
       } else {

sources/corepackUtils.ts

@@ -19,6 +19,12 @@ import * as npmRegistryUtils                                   from './npmRegist
 import {RegistrySpec, Descriptor, Locator, PackageManagerSpec} from './types';
 import {BinList, BinSpec, InstallSpec, DownloadSpec}           from './types';
 
+const YARN_SWITCH_REGEX = /[/\\]switch[/\\]bin[/\\]/;
+
+export function isYarnSwitchPath(p: string) {
+  return YARN_SWITCH_REGEX.test(p);
+}
+
 export function getRegistryFromPackageManagerSpec(spec: PackageManagerSpec) {
   return process.env.COREPACK_NPM_REGISTRY
     ? spec.npmRegistry ?? spec.registry

tests/Disable.test.ts

@@ -97,4 +97,23 @@ describe(`DisableCommand`, () => {
       await expect(sortedEntries).resolves.toEqual([...binNames].sort());
     });
   });
+
+  it(`shouldn't remove Yarn binaries if they are in a /switch/ folder`, async () => {
+    await xfs.mktempPromise(async cwd => {
+      await xfs.mkdirPromise(ppath.join(cwd, `switch/bin`), {recursive: true});
+      await xfs.writeFilePromise(ppath.join(cwd, `switch/bin/yarn`), `hello`);
+
+      await xfs.linkPromise(
+        ppath.join(cwd, `switch/bin/yarn`),
+        ppath.join(cwd, `yarn`),
+      );
+
+      await expect(runCli(cwd, [`disable`])).resolves.toMatchObject({
+        exitCode: 0,
+      });
+
+      const file = await xfs.readFilePromise(ppath.join(cwd, `yarn`), `utf8`);
+      expect(file).toBe(`hello`);
+    });
+  });
 });

tests/Enable.test.ts

@@ -1,7 +1,7 @@
 import {Filename, ppath, xfs, npath}                                    from '@yarnpkg/fslib';
 import {delimiter}                                                      from 'node:path';
 import process                                                          from 'node:process';
-import {describe, beforeEach, it, expect}                               from 'vitest';
+import {describe, beforeEach, it, expect, test}                         from 'vitest';
 
 import {Engine}                                                         from '../sources/Engine';
 import {SupportedPackageManagers, SupportedPackageManagerSetWithoutNpm} from '../sources/types';
@@ -87,4 +87,42 @@ describe(`EnableCommand`, () => {
       await expect(sortedEntries).resolves.toEqual(expectedEntries.sort());
     });
   });
+
+  test.skipIf(process.platform === `win32`)(`should overwrite existing files`, async () => {
+    await xfs.mktempPromise(async cwd => {
+      await xfs.writeFilePromise(ppath.join(cwd, `yarn`), `hello`);
+
+      process.env.PATH = `${npath.fromPortablePath(cwd)}${delimiter}${process.env.PATH}`;
+      await expect(runCli(cwd, [`enable`])).resolves.toMatchObject({
+        stdout: ``,
+        stderr: ``,
+        exitCode: 0,
+      });
+
+      const file = await xfs.readFilePromise(ppath.join(cwd, `yarn`), `utf8`);
+      expect(file).toBe(`hello`);
+    });
+  });
+
+  test.skipIf(process.platform === `win32`)(`shouldn't overwrite Yarn files if they are in a /switch/ folder`, async () => {
+    await xfs.mktempPromise(async cwd => {
+      await xfs.mkdirPromise(ppath.join(cwd, `switch/bin`), {recursive: true});
+      await xfs.writeFilePromise(ppath.join(cwd, `switch/bin/yarn`), `hello`);
+
+      await xfs.linkPromise(
+        ppath.join(cwd, `switch/bin/yarn`),
+        ppath.join(cwd, `yarn`),
+      );
+
+      process.env.PATH = `${npath.fromPortablePath(cwd)}${delimiter}${process.env.PATH}`;
+      await expect(runCli(cwd, [`enable`])).resolves.toMatchObject({
+        stdout: ``,
+        stderr: ``,
+        exitCode: 0,
+      });
+
+      const file = await xfs.readFilePromise(ppath.join(cwd, `yarn`), `utf8`);
+      expect(file).toBe(`hello`);
+    });
+  });
 });