fix(fslib): handle symlinks to zip files (#6603)

This is the same as #5474 but
allows edits by maintainer

**What's the problem this PR addresses?**
<!-- Describe the rationale of your PR. -->
Yarn shouldn't care if zips in the cache are symlinks or not. The only
reason it doesn't work is that finding the mount point skips zips if
they're not regular files. This used to be supported until it was
removed for "performance" reasons in
#1474. The bulk of the logic in the
linked PR involves resolving the real path of the symlink but I don't
think that's needed for this?

<!-- Link all issues that it closes. (Closes/Resolves #xxxx.) -->
Resolves #3514
Closes #5474 (supersedes it)

**How did you fix it?**
I switched the check to use `stat` from `lstat`.

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---------

Co-authored-by: merceyz <merceyz@users.noreply.github.com>

Author: thatsmydoing

.pnp.cjs

@@ -0,0 +1,39 @@
+releases:
+  "@yarnpkg/cli": patch
+  "@yarnpkg/core": patch
+  "@yarnpkg/fslib": patch
+  "@yarnpkg/pnp": patch
+
+declined:
+  - "@yarnpkg/plugin-compat"
+  - "@yarnpkg/plugin-constraints"
+  - "@yarnpkg/plugin-dlx"
+  - "@yarnpkg/plugin-essentials"
+  - "@yarnpkg/plugin-exec"
+  - "@yarnpkg/plugin-file"
+  - "@yarnpkg/plugin-git"
+  - "@yarnpkg/plugin-github"
+  - "@yarnpkg/plugin-http"
+  - "@yarnpkg/plugin-init"
+  - "@yarnpkg/plugin-interactive-tools"
+  - "@yarnpkg/plugin-link"
+  - "@yarnpkg/plugin-nm"
+  - "@yarnpkg/plugin-npm"
+  - "@yarnpkg/plugin-npm-cli"
+  - "@yarnpkg/plugin-pack"
+  - "@yarnpkg/plugin-patch"
+  - "@yarnpkg/plugin-pnp"
+  - "@yarnpkg/plugin-pnpm"
+  - "@yarnpkg/plugin-stage"
+  - "@yarnpkg/plugin-typescript"
+  - "@yarnpkg/plugin-version"
+  - "@yarnpkg/plugin-workspace-tools"
+  - vscode-zipfs
+  - "@yarnpkg/builder"
+  - "@yarnpkg/doctor"
+  - "@yarnpkg/extensions"
+  - "@yarnpkg/libzip"
+  - "@yarnpkg/nm"
+  - "@yarnpkg/pnpify"
+  - "@yarnpkg/sdks"
+  - "@yarnpkg/shell"

.yarn/versions/757578fa.yml

@@ -109,6 +109,33 @@ describe(`Commands`, () => {
       }),
     );
 
+    tests.testIf(
+      () => process.platform !== `win32`,
+      `it should install from zips that are symlinks`,
+      makeTemporaryEnv({
+        dependencies: {
+          [`no-deps`]: `1.0.0`,
+        },
+      }, async ({path, run, source}) => {
+        await run(`install`);
+
+        const allFiles = await xfs.readdirPromise(ppath.join(path, `.yarn/cache`));
+        const zipFiles = allFiles.filter(file => file.endsWith(`.zip`));
+
+        await xfs.mkdirPromise(ppath.join(path, `store`));
+        for (const filename of zipFiles) {
+          const zipFile = ppath.join(path, `.yarn/cache`, filename);
+          const storePath = ppath.join(path, `store`, filename);
+          await xfs.movePromise(zipFile, storePath);
+          await xfs.symlinkPromise(storePath, zipFile);
+        }
+
+        await xfs.removePromise(ppath.join(path, Filename.pnpCjs));
+
+        await run(`install`, `--immutable`);
+      }),
+    );
+
     test(
       `it should refuse to create a lockfile when using --immutable`,
       makeTemporaryEnv({

packages/acceptance-tests/pkg-tests-specs/sources/commands/install.test.ts

@@ -2253,4 +2253,31 @@ describe(`Plug'n'Play`, () => {
       });
     }),
   );
+
+  testIf(
+    () => process.platform !== `win32`,
+    `it can resolve files from zips that are symlinks`,
+    makeTemporaryEnv({
+      dependencies: {
+        [`no-deps`]: `1.0.0`,
+      },
+    }, async ({path, run, source}) => {
+      await run(`install`);
+
+      const allFiles = await xfs.readdirPromise(ppath.join(path, `.yarn/cache`));
+      const zipFiles = allFiles.filter(file => file.endsWith(`.zip`));
+
+      await xfs.mkdirPromise(ppath.join(path, `store`));
+      for (const filename of zipFiles) {
+        const zipFile = ppath.join(path, `.yarn/cache`, filename);
+        const storePath = ppath.join(path, `store`, filename);
+        await xfs.movePromise(zipFile, storePath);
+        await xfs.symlinkPromise(storePath, zipFile);
+      }
+
+      await expect(
+        source(`require('no-deps')`),
+      ).resolves.toEqual({name: `no-deps`, version: `1.0.0`});
+    }),
+  );
 });

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

@@ -1013,7 +1013,7 @@ export class MountFS<MountedFS extends MountableFS> extends BasePortableFakeFS {
           continue;
 
         try {
-          if (this.typeCheck !== null && (this.baseFs.lstatSync(filePath).mode & constants.S_IFMT) !== this.typeCheck) {
+          if (this.typeCheck !== null && (this.baseFs.statSync(filePath).mode & constants.S_IFMT) !== this.typeCheck) {
             this.notMount.add(filePath);
             continue;
           }

packages/yarnpkg-core/sources/worker-zip/index.js

@@ -13,10 +13,15 @@ export const ZIP_DIR3 = ppath.join(
   npath.toPortablePath(__dirname),
   `fixtures/foo.hiddenzip` as Filename,
 );
+export const ZIP_DIR4 = ppath.join(
+  npath.toPortablePath(__dirname),
+  `fixtures/symlink.zip` as Filename,
+);
 
 export const ZIP_FILE1 = ppath.join(ZIP_DIR1, `foo.txt`);
 export const ZIP_FILE2 = ppath.join(ZIP_DIR2, `foo.txt`);
 export const ZIP_FILE3 = ppath.join(ZIP_DIR3, `foo.txt`);
+export const ZIP_FILE4 = ppath.join(ZIP_DIR4, `foo.txt`);
 
 afterEach(() => {
   jest.useRealTimers();
@@ -81,6 +86,14 @@ describe(`ZipOpenFS`, () => {
     fs.discardAndClose();
   });
 
+  it(`can read from a zip file that's a symlink`, () => {
+    const fs = new ZipOpenFS();
+
+    expect(fs.readFileSync(ZIP_FILE4, `utf8`)).toEqual(`foo\n`);
+
+    fs.discardAndClose();
+  });
+
   it(`doesn't close a ZipFS instance with open handles`, () => {
     const fs = new ZipOpenFS({maxOpenFiles: 1});
 

packages/yarnpkg-fslib/sources/MountFS.ts

@@ -0,0 +1 @@
+symlink-source.zip