From a848cd5ce4625b73fcbb26f2924a675ef26727e9 Mon Sep 17 00:00:00 2001
From: Phil Pluckthun <phil@kitten.sh>
Date: Sat, 11 Apr 2026 01:30:09 +0100
Subject: [PATCH 1/6] Prenormalize symlink target to normal and remove weakmap
 cache

The WeakMap is likely more expensive and this can leave unnormalized
absolute paths in the file map cache.

NOTE: This bumps the `CACHE_BREAKER` value!
---
 .../src/crawlers/watchman/index.js            |  6 ++++
 packages/metro-file-map/src/index.js          |  7 +++--
 .../metro-file-map/src/lib/RootPathUtils.js   | 24 +++++++++++++++
 packages/metro-file-map/src/lib/TreeFS.js     | 29 ++++---------------
 4 files changed, 40 insertions(+), 26 deletions(-)

diff --git a/packages/metro-file-map/src/crawlers/watchman/index.js b/packages/metro-file-map/src/crawlers/watchman/index.js
index 2e45eba592..41c7f05841 100644
--- a/packages/metro-file-map/src/crawlers/watchman/index.js
+++ b/packages/metro-file-map/src/crawlers/watchman/index.js
@@ -327,6 +327,12 @@ export default async function watchmanCrawl({
         if (fileData.type === 'l') {
           symlinkInfo = fileData['symlink_target'] ?? 1;
         }
+        if (typeof symlinkInfo === 'string') {
+          symlinkInfo = pathUtils.resolveSymlinkToNormal(
+            relativeFilePath,
+            symlinkInfo,
+          );
+        }
 
         const nextData: FileMetadata = [
           mtime,
diff --git a/packages/metro-file-map/src/index.js b/packages/metro-file-map/src/index.js
index 113f85be1d..53d5febbf2 100644
--- a/packages/metro-file-map/src/index.js
+++ b/packages/metro-file-map/src/index.js
@@ -155,7 +155,7 @@ export type {
 // This should be bumped whenever a code change to `metro-file-map` itself
 // would cause a change to the cache data structure and/or content (for a given
 // filesystem state and build parameters).
-const CACHE_BREAKER = '11';
+const CACHE_BREAKER = '12';
 
 const CHANGE_INTERVAL = 30;
 
@@ -565,7 +565,10 @@ export default class FileMap extends EventEmitter {
         .readlink(this.#pathUtils.normalToAbsolute(normalPath))
         .then(symlinkTarget => {
           fileMetadata[H.VISITED] = 1;
-          fileMetadata[H.SYMLINK] = symlinkTarget;
+          fileMetadata[H.SYMLINK] = this.#pathUtils.resolveSymlinkToNormal(
+            normalPath,
+            symlinkTarget,
+          );
         });
     }
     return null;
diff --git a/packages/metro-file-map/src/lib/RootPathUtils.js b/packages/metro-file-map/src/lib/RootPathUtils.js
index 5720d60ee9..53a321111a 100644
--- a/packages/metro-file-map/src/lib/RootPathUtils.js
+++ b/packages/metro-file-map/src/lib/RootPathUtils.js
@@ -8,6 +8,7 @@
  * @format
  */
 
+import normalizePathSeparatorsToSystem from './normalizePathSeparatorsToSystem';
 import invariant from 'invariant';
 import * as path from 'path';
 
@@ -166,6 +167,29 @@ export class RootPathUtils {
     );
   }
 
+  resolveSymlinkToNormal(
+    symlinkNormalPath: string,
+    readlinkResult: string,
+  ): string {
+    let target = normalizePathSeparatorsToSystem(readlinkResult);
+    // WARN: This only applies to Windows + Node 20 case, where the value is completely
+    // unnormalized and a trailing slash may be returned
+    if (target[target.length - 1] === path.sep) {
+      target = target.slice(0, -1);
+    }
+    if (path.isAbsolute(target)) {
+      return this.absoluteToNormal(target);
+    }
+    // Resolve relative to the symlink's containing directory, expressed as
+    // a root-relative (possibly non-normal) path, then normalize
+    const sepIdx = symlinkNormalPath.lastIndexOf(path.sep);
+    const rootRelativeTarget =
+      sepIdx === -1
+        ? target
+        : symlinkNormalPath.slice(0, sepIdx) + path.sep + target;
+    return this.relativeToNormal(rootRelativeTarget);
+  }
+
   // If a path is a direct ancestor of the project root (or the root itself),
   // return a number with the degrees of separation, e.g. root=0, parent=1,..
   // or null otherwise.
diff --git a/packages/metro-file-map/src/lib/TreeFS.js b/packages/metro-file-map/src/lib/TreeFS.js
index 7b1691ae2c..05f06f36c4 100644
--- a/packages/metro-file-map/src/lib/TreeFS.js
+++ b/packages/metro-file-map/src/lib/TreeFS.js
@@ -124,8 +124,6 @@ type MetadataIteratorOptions = Readonly<{
  *   a trailing slash
  */
 export default class TreeFS implements MutableFileSystem {
-  +#cachedNormalSymlinkTargets: WeakMap<FileNode, NormalizedSymlinkTarget> =
-    new WeakMap();
   +#pathUtils: RootPathUtils;
   +#processFile: ProcessFileFunction;
   +#rootDir: Path;
@@ -1214,33 +1212,16 @@ export default class TreeFS implements MutableFileSystem {
     symlinkNode: FileMetadata,
     canonicalPathOfSymlink: Path,
   ): NormalizedSymlinkTarget {
-    const cachedResult = this.#cachedNormalSymlinkTargets.get(symlinkNode);
-    if (cachedResult != null) {
-      return cachedResult;
-    }
-
-    const literalSymlinkTarget = symlinkNode[H.SYMLINK];
+    const symlinkTarget = symlinkNode[H.SYMLINK];
     invariant(
-      typeof literalSymlinkTarget === 'string',
+      typeof symlinkTarget === 'string',
       'Expected symlink target to be populated.',
     );
-    const absoluteSymlinkTarget = path.resolve(
-      this.#rootDir,
-      canonicalPathOfSymlink,
-      '..', // Symlink target is relative to its containing directory.
-      literalSymlinkTarget, // May be absolute, in which case the above are ignored
-    );
-    const normalSymlinkTarget = path.relative(
-      this.#rootDir,
-      absoluteSymlinkTarget,
-    );
     const result = {
-      ancestorOfRootIdx:
-        this.#pathUtils.getAncestorOfRootIdx(normalSymlinkTarget),
-      normalPath: normalSymlinkTarget,
-      startOfBasenameIdx: normalSymlinkTarget.lastIndexOf(path.sep) + 1,
+      ancestorOfRootIdx: this.#pathUtils.getAncestorOfRootIdx(symlinkTarget),
+      normalPath: symlinkTarget,
+      startOfBasenameIdx: symlinkTarget.lastIndexOf(path.sep) + 1,
     };
-    this.#cachedNormalSymlinkTargets.set(symlinkNode, result);
     return result;
   }
 

From d3fd493016add66694e88803b581ceba0f7a072b Mon Sep 17 00:00:00 2001
From: Phil Pluckthun <phil@kitten.sh>
Date: Sat, 11 Apr 2026 01:34:36 +0100
Subject: [PATCH 2/6] Normalize stored value to posix

This keeps the metro-file-map value system-stable. Before they could
store absolute paths, and system paths, however, this is now normalized
to posix normal paths.
---
 packages/metro-file-map/src/crawlers/watchman/index.js | 5 ++---
 packages/metro-file-map/src/index.js                   | 5 ++---
 packages/metro-file-map/src/lib/TreeFS.js              | 4 +++-
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/packages/metro-file-map/src/crawlers/watchman/index.js b/packages/metro-file-map/src/crawlers/watchman/index.js
index 41c7f05841..dbfbab37ca 100644
--- a/packages/metro-file-map/src/crawlers/watchman/index.js
+++ b/packages/metro-file-map/src/crawlers/watchman/index.js
@@ -328,9 +328,8 @@ export default async function watchmanCrawl({
           symlinkInfo = fileData['symlink_target'] ?? 1;
         }
         if (typeof symlinkInfo === 'string') {
-          symlinkInfo = pathUtils.resolveSymlinkToNormal(
-            relativeFilePath,
-            symlinkInfo,
+          symlinkInfo = normalizePathSeparatorsToPosix(
+            pathUtils.resolveSymlinkToNormal(relativeFilePath, symlinkInfo),
           );
         }
 
diff --git a/packages/metro-file-map/src/index.js b/packages/metro-file-map/src/index.js
index 53d5febbf2..5eda1e0e0a 100644
--- a/packages/metro-file-map/src/index.js
+++ b/packages/metro-file-map/src/index.js
@@ -565,9 +565,8 @@ export default class FileMap extends EventEmitter {
         .readlink(this.#pathUtils.normalToAbsolute(normalPath))
         .then(symlinkTarget => {
           fileMetadata[H.VISITED] = 1;
-          fileMetadata[H.SYMLINK] = this.#pathUtils.resolveSymlinkToNormal(
-            normalPath,
-            symlinkTarget,
+          fileMetadata[H.SYMLINK] = normalizePathSeparatorsToPosix(
+            this.#pathUtils.resolveSymlinkToNormal(normalPath, symlinkTarget),
           );
         });
     }
diff --git a/packages/metro-file-map/src/lib/TreeFS.js b/packages/metro-file-map/src/lib/TreeFS.js
index 05f06f36c4..9cabab0d41 100644
--- a/packages/metro-file-map/src/lib/TreeFS.js
+++ b/packages/metro-file-map/src/lib/TreeFS.js
@@ -21,6 +21,7 @@ import type {
 } from '../flow-types';
 
 import H from '../constants';
+import normalizePathSeparatorsToSystem from './normalizePathSeparatorsToSystem';
 import {RootPathUtils} from './RootPathUtils';
 import invariant from 'invariant';
 import path from 'path';
@@ -1212,11 +1213,12 @@ export default class TreeFS implements MutableFileSystem {
     symlinkNode: FileMetadata,
     canonicalPathOfSymlink: Path,
   ): NormalizedSymlinkTarget {
-    const symlinkTarget = symlinkNode[H.SYMLINK];
+    let symlinkTarget = symlinkNode[H.SYMLINK];
     invariant(
       typeof symlinkTarget === 'string',
       'Expected symlink target to be populated.',
     );
+    symlinkTarget = normalizePathSeparatorsToSystem(symlinkTarget);
     const result = {
       ancestorOfRootIdx: this.#pathUtils.getAncestorOfRootIdx(symlinkTarget),
       normalPath: symlinkTarget,

From e8a016c1e2f94b3105215f0d28fdb500ebc74eb4 Mon Sep 17 00:00:00 2001
From: Phil Pluckthun <phil@kitten.sh>
Date: Sat, 11 Apr 2026 01:43:01 +0100
Subject: [PATCH 3/6] Add/update unit tests

---
 .../src/lib/__tests__/RootPathUtils-test.js   | 41 ++++++++++++
 .../src/lib/__tests__/TreeFS-test.js          | 66 ++++++++-----------
 2 files changed, 69 insertions(+), 38 deletions(-)

diff --git a/packages/metro-file-map/src/lib/__tests__/RootPathUtils-test.js b/packages/metro-file-map/src/lib/__tests__/RootPathUtils-test.js
index 8fb693c498..d71f3abd36 100644
--- a/packages/metro-file-map/src/lib/__tests__/RootPathUtils-test.js
+++ b/packages/metro-file-map/src/lib/__tests__/RootPathUtils-test.js
@@ -153,4 +153,45 @@ describe.each([['win32'], ['posix']])('RootPathUtils on %s', platform => {
   ])('getAncestorOfRootIdx (%s => %s)', (input, expected) => {
     expect(pathUtils.getAncestorOfRootIdx(input)).toEqual(expected);
   });
+
+  describe('resolveSymlinkToNormal', () => {
+    beforeEach(() => {
+      pathUtils = new RootPathUtils(p('/project/root'));
+    });
+
+    test.each([
+      ['foo/link', './target.js', p('foo/target.js')],
+      ['foo/link', '../bar.js', 'bar.js'],
+      ['link', 'target.js', 'target.js'],
+      [p('a/b/link'), p('../../c.js'), 'c.js'],
+      [p('a/b/link'), p('../../../outside/f.js'), p('../outside/f.js')],
+    ])(
+      'resolves relative target (%s -> %s) to %s',
+      (symlinkPath, readlinkResult, expected) => {
+        expect(
+          pathUtils.resolveSymlinkToNormal(p(symlinkPath), readlinkResult),
+        ).toEqual(expected);
+      },
+    );
+
+    test.each([
+      ['link', p('/project/root/target.js'), 'target.js'],
+      ['link', p('/project/root/a/b.js'), p('a/b.js')],
+      ['link', p('/outside/foo.js'), p('../../outside/foo.js')],
+      [p('a/link'), p('/project/root'), ''],
+    ])(
+      'resolves absolute target (%s -> %s) to %s',
+      (symlinkPath, readlinkResult, expected) => {
+        expect(
+          pathUtils.resolveSymlinkToNormal(p(symlinkPath), readlinkResult),
+        ).toEqual(expected);
+      },
+    );
+
+    test('strips trailing separator from target', () => {
+      expect(
+        pathUtils.resolveSymlinkToNormal('link', p('/project/root/dir/')),
+      ).toEqual('dir');
+    });
+  });
 });
diff --git a/packages/metro-file-map/src/lib/__tests__/TreeFS-test.js b/packages/metro-file-map/src/lib/__tests__/TreeFS-test.js
index a65eab4293..5bdc3a0869 100644
--- a/packages/metro-file-map/src/lib/__tests__/TreeFS-test.js
+++ b/packages/metro-file-map/src/lib/__tests__/TreeFS-test.js
@@ -41,18 +41,18 @@ describe.each([['win32'], ['posix']])('TreeFS on %s', platform => {
       rootDir: p('/project'),
       files: new Map<CanonicalPath, FileMetadata>([
         [p('foo/another.js'), [123, 2, 0, null, 0, 'another']],
-        [p('foo/owndir'), [0, 0, 0, null, '.', null]],
-        [p('foo/link-to-bar.js'), [0, 0, 0, null, p('../bar.js'), null]],
-        [p('foo/link-to-another.js'), [0, 0, 0, null, p('another.js'), null]],
+        [p('foo/owndir'), [0, 0, 0, null, 'foo', null]],
+        [p('foo/link-to-bar.js'), [0, 0, 0, null, 'bar.js', null]],
+        [p('foo/link-to-another.js'), [0, 0, 0, null, 'foo/another.js', null]],
         [p('../outside/external.js'), [0, 0, 0, null, 0, null]],
         [p('bar.js'), [234, 3, 0, null, 0, 'bar']],
-        [p('link-to-foo'), [456, 0, 0, null, p('./../project/foo'), null]],
-        [p('abs-link-out'), [456, 0, 0, null, p('/outside/./baz/..'), null]],
+        [p('link-to-foo'), [456, 0, 0, null, 'foo', null]],
+        [p('abs-link-out'), [456, 0, 0, null, '../outside', null]],
         [p('root'), [0, 0, 0, null, '..', null]],
-        [p('link-to-nowhere'), [123, 0, 0, null, p('./nowhere'), null]],
-        [p('link-to-self'), [123, 0, 0, null, p('./link-to-self'), null]],
-        [p('link-cycle-1'), [123, 0, 0, null, p('./link-cycle-2'), null]],
-        [p('link-cycle-2'), [123, 0, 0, null, p('./link-cycle-1'), null]],
+        [p('link-to-nowhere'), [123, 0, 0, null, 'nowhere', null]],
+        [p('link-to-self'), [123, 0, 0, null, 'link-to-self', null]],
+        [p('link-cycle-1'), [123, 0, 0, null, 'link-cycle-2', null]],
+        [p('link-cycle-2'), [123, 0, 0, null, 'link-cycle-1', null]],
         [p('node_modules/pkg/a.js'), [123, 0, 0, null, 0, 'a']],
         [p('node_modules/pkg/package.json'), [123, 0, 0, null, 0, 'pkg']],
       ]),
@@ -194,7 +194,7 @@ describe.each([['win32'], ['posix']])('TreeFS on %s', platform => {
         rootDir: p('/deep/project/root'),
         files: new Map<CanonicalPath, FileMetadata>([
           [p('foo/index.js'), [123, 0, 0, null, 0, null]],
-          [p('link-up'), [123, 0, 0, null, p('..'), null]],
+          [p('link-up'), [123, 0, 0, null, '..', null]],
         ]),
         processFile: () => {
           throw new Error('Not implemented');
@@ -221,7 +221,7 @@ describe.each([['win32'], ['posix']])('TreeFS on %s', platform => {
 
   describe('symlinks to an ancestor of the project root', () => {
     beforeEach(() => {
-      tfs.addOrModify(p('foo/link-up-2'), [0, 0, 0, null, p('../..'), null]);
+      tfs.addOrModify(p('foo/link-up-2'), [0, 0, 0, null, '..', null]);
     });
 
     test.each([
@@ -277,14 +277,14 @@ describe.each([['win32'], ['posix']])('TreeFS on %s', platform => {
     test('returns changed (inc. new) and removed files in given FileData', () => {
       const newFiles: FileData = new Map<CanonicalPath, FileMetadata>([
         [p('new-file'), [789, 0, 0, null, 0, null]],
-        [p('link-to-foo'), [456, 0, 0, null, p('./foo'), null]],
+        [p('link-to-foo'), [456, 0, 0, null, 'foo', null]],
         // Different modified time, expect new mtime in changedFiles
         [p('foo/another.js'), [124, 0, 0, null, 0, null]],
-        [p('link-cycle-1'), [123, 0, 0, null, p('./link-cycle-2'), null]],
-        [p('link-cycle-2'), [123, 0, 0, null, p('./link-cycle-1'), null]],
+        [p('link-cycle-1'), [123, 0, 0, null, 'link-cycle-2', null]],
+        [p('link-cycle-2'), [123, 0, 0, null, 'link-cycle-1', null]],
         // Was a symlink, now a regular file
         [p('link-to-self'), [123, 0, 0, null, 0, null]],
-        [p('link-to-nowhere'), [123, 0, 0, null, p('./nowhere'), null]],
+        [p('link-to-nowhere'), [123, 0, 0, null, 'nowhere', null]],
         [p('node_modules/pkg/a.js'), [123, 0, 0, null, 0, 'a']],
         [p('node_modules/pkg/package.json'), [123, 0, 0, null, 0, 'pkg']],
       ]);
@@ -393,24 +393,18 @@ describe.each([['win32'], ['posix']])('TreeFS on %s', platform => {
             [
               [
                 p('a/1/package.json'),
-                [0, 0, 0, null, './real-package.json', null],
+                [0, 0, 0, null, 'a/1/real-package.json', null],
               ],
               [
                 p('a/2/package.json'),
-                [0, 0, 0, null, './notexist-package.json', null],
-              ],
-              [p('a/b/c/d/link-to-C'), [0, 0, 0, null, p('../../../..'), null]],
-              [
-                p('a/b/c/d/link-to-B'),
-                [0, 0, 0, null, p('../../../../..'), null],
-              ],
-              [
-                p('a/b/c/d/link-to-A'),
-                [0, 0, 0, null, p('../../../../../..'), null],
+                [0, 0, 0, null, 'a/2/notexist-package.json', null],
               ],
+              [p('a/b/c/d/link-to-C'), [0, 0, 0, null, '', null]],
+              [p('a/b/c/d/link-to-B'), [0, 0, 0, null, '..', null]],
+              [p('a/b/c/d/link-to-A'), [0, 0, 0, null, '../..', null]],
               [
                 p('n_m/workspace/link-to-pkg'),
-                [0, 0, 0, null, p('../../../workspace-pkg'), null],
+                [0, 0, 0, null, '../workspace-pkg', null],
               ],
             ] as Array<[CanonicalPath, FileMetadata]>
           ).concat(
@@ -817,7 +811,7 @@ describe.each([['win32'], ['posix']])('TreeFS on %s', platform => {
           new Map<CanonicalPath, FileMetadata>([
             [
               p('newdir/link-to-link-to-bar.js'),
-              [0, 0, 0, null, p('../foo/link-to-bar.js'), null],
+              [0, 0, 0, null, 'foo/link-to-bar.js', null],
             ],
             [p('foo/baz.js'), [0, 0, 0, null, 0, null]],
             [p('bar.js'), [999, 1, 0, null, 0, null]],
@@ -967,7 +961,7 @@ describe.each([['win32'], ['posix']])('TreeFS on %s', platform => {
           {
             baseName: 'link-to-bar.js',
             canonicalPath: p('foo/link-to-bar.js'),
-            metadata: [0, 0, 0, null, p('../bar.js'), null],
+            metadata: [0, 0, 0, null, 'bar.js', null],
           },
         ]),
       );
@@ -983,7 +977,7 @@ describe.each([['win32'], ['posix']])('TreeFS on %s', platform => {
         files: new Map<CanonicalPath, FileMetadata>([
           [p('foo.js'), [123, 0, 0, 'def456', 0, null]],
           [p('bar.js'), [123, 0, 0, null, 0, null]],
-          [p('link-to-bar'), [456, 0, 0, null, p('./bar.js'), null]],
+          [p('link-to-bar'), [456, 0, 0, null, 'bar.js', null]],
         ]),
         processFile: mockProcessFile,
       });
@@ -1084,7 +1078,7 @@ describe.each([['win32'], ['posix']])('TreeFS on %s', platform => {
         files: new Map<CanonicalPath, FileMetadata>([
           [p('existing.js'), [123, 0, 0, '', 0]],
           [p('dir/nested.js'), [456, 0, 0, '', 0]],
-          [p('mylink'), [0, 0, 0, '', p('./dir')]],
+          [p('mylink'), [0, 0, 0, '', 'dir']],
         ]),
         processFile: () => {
           throw new Error('Not implemented');
@@ -1214,23 +1208,19 @@ describe.each([['win32'], ['posix']])('TreeFS on %s', platform => {
       test('tracks added files when adding a symlink', () => {
         simpleTfs.addOrModify(
           p('link-to-existing'),
-          [0, 0, 0, '', p('./existing.js')],
+          [0, 0, 0, '', 'existing.js'],
           listener,
         );
 
         expect(logChange.mock.calls).toEqual([
-          [
-            'fileAdded',
-            p('link-to-existing'),
-            [0, 0, 0, '', p('./existing.js')],
-          ],
+          ['fileAdded', p('link-to-existing'), [0, 0, 0, '', 'existing.js']],
         ]);
       });
 
       test('tracks removed symlinks with their metadata', () => {
         simpleTfs.remove(p('mylink'), listener);
         expect(logChange.mock.calls).toEqual([
-          ['fileRemoved', p('mylink'), [0, 0, 0, '', p('./dir')]],
+          ['fileRemoved', p('mylink'), [0, 0, 0, '', 'dir']],
         ]);
       });
     });

From e14f40a7ef8e197aa366ce7185bde078086576a7 Mon Sep 17 00:00:00 2001
From: Phil Pluckthun <phil@kitten.sh>
Date: Sat, 11 Apr 2026 01:44:24 +0100
Subject: [PATCH 4/6] Rebuild ts-defs

---
 packages/metro-file-map/types/lib/RootPathUtils.d.ts | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/packages/metro-file-map/types/lib/RootPathUtils.d.ts b/packages/metro-file-map/types/lib/RootPathUtils.d.ts
index 79d65e0262..ff91c9b41d 100644
--- a/packages/metro-file-map/types/lib/RootPathUtils.d.ts
+++ b/packages/metro-file-map/types/lib/RootPathUtils.d.ts
@@ -5,7 +5,7 @@
  * LICENSE file in the root directory of this source tree.
  *
  * @noformat
- * @generated SignedSource<<5ecdb559fce5f5c6ed50df6e4eaebf20>>
+ * @generated SignedSource<<de7026bc6d3d1406108afc1b07d26f32>>
  *
  * This file was translated from Flow by scripts/generateTypeScriptDefinitions.js
  * Original file: packages/metro-file-map/src/lib/RootPathUtils.js
@@ -21,6 +21,10 @@ export declare class RootPathUtils {
   absoluteToNormal(absolutePath: string): string;
   normalToAbsolute(normalPath: string): string;
   relativeToNormal(relativePath: string): string;
+  resolveSymlinkToNormal(
+    symlinkNormalPath: string,
+    readlinkResult: string,
+  ): string;
   getAncestorOfRootIdx(normalPath: string): null | undefined | number;
   joinNormalToRelative(
     normalPath: string,

From 0a6435120887217ecc560ff35f7a5272cee6a9b8 Mon Sep 17 00:00:00 2001
From: Phil Pluckthun <phil@kitten.sh>
Date: Wed, 22 Apr 2026 09:01:54 +0100
Subject: [PATCH 5/6] Drop intermediate data structure in
 resolveSymlinkTargetToNormalPath

---
 packages/metro-file-map/src/lib/TreeFS.js | 29 +++++++----------------
 1 file changed, 9 insertions(+), 20 deletions(-)

diff --git a/packages/metro-file-map/src/lib/TreeFS.js b/packages/metro-file-map/src/lib/TreeFS.js
index 9cabab0d41..d8bd57f8ca 100644
--- a/packages/metro-file-map/src/lib/TreeFS.js
+++ b/packages/metro-file-map/src/lib/TreeFS.js
@@ -38,12 +38,6 @@ function isRegularFile(node: FileNode): boolean {
   return node[H.SYMLINK] === 0;
 }
 
-type NormalizedSymlinkTarget = {
-  ancestorOfRootIdx: ?number,
-  normalPath: string,
-  startOfBasenameIdx: number,
-};
-
 type DeserializedSnapshotInput = {
   rootDir: string,
   fileSystemData: DirectoryNode,
@@ -728,7 +722,7 @@ export default class TreeFS implements MutableFileSystem {
         // Append any subsequent path segments to the symlink target, and reset
         // with our new target.
         const joinedResult = this.#pathUtils.joinNormalToRelative(
-          normalSymlinkTarget.normalPath,
+          normalSymlinkTarget,
           remainingTargetPath,
         );
 
@@ -744,12 +738,13 @@ export default class TreeFS implements MutableFileSystem {
         // with the remaining path results in collapsing segments, e.g:
         // '../..' + 'parentofroot/root/foo.js' = 'foo.js', then we must add
         // parentofroot and root as ancestors.
+        ancestorOfRootIdx =
+          this.#pathUtils.getAncestorOfRootIdx(normalSymlinkTarget);
         if (
           collectAncestors &&
           !isLastSegment &&
           // No-op optimisation to bail out the common case of nothing to do.
-          (normalSymlinkTarget.ancestorOfRootIdx === 0 ||
-            joinedResult.collapsedSegments > 0)
+          (ancestorOfRootIdx === 0 || joinedResult.collapsedSegments > 0)
         ) {
           let node: MixedNode = this.#rootNode;
           let collapsedPath = '';
@@ -764,7 +759,7 @@ export default class TreeFS implements MutableFileSystem {
               // Add the root only if the target is the root or we have
               // collapsed segments.
               i > 0 ||
-              normalSymlinkTarget.ancestorOfRootIdx === 0 ||
+              ancestorOfRootIdx === 0 ||
               joinedResult.collapsedSegments > 0
             ) {
               reverseAncestors.push({
@@ -787,7 +782,7 @@ export default class TreeFS implements MutableFileSystem {
         // the symlink target, and start collecting ancestors only
         // from the target itself (ie, the basename of the normal target path)
         // onwards.
-        unseenPathFromIdx = normalSymlinkTarget.startOfBasenameIdx;
+        unseenPathFromIdx = normalSymlinkTarget.lastIndexOf(path.sep) + 1;
 
         if (seen == null) {
           // Optimisation: set this lazily only when we've encountered a symlink
@@ -1212,19 +1207,13 @@ export default class TreeFS implements MutableFileSystem {
   #resolveSymlinkTargetToNormalPath(
     symlinkNode: FileMetadata,
     canonicalPathOfSymlink: Path,
-  ): NormalizedSymlinkTarget {
-    let symlinkTarget = symlinkNode[H.SYMLINK];
+  ): Path {
+    const symlinkTarget = symlinkNode[H.SYMLINK];
     invariant(
       typeof symlinkTarget === 'string',
       'Expected symlink target to be populated.',
     );
-    symlinkTarget = normalizePathSeparatorsToSystem(symlinkTarget);
-    const result = {
-      ancestorOfRootIdx: this.#pathUtils.getAncestorOfRootIdx(symlinkTarget),
-      normalPath: symlinkTarget,
-      startOfBasenameIdx: symlinkTarget.lastIndexOf(path.sep) + 1,
-    };
-    return result;
+    return normalizePathSeparatorsToSystem(symlinkTarget);
   }
 
   #getFileData(

From 32f7bd45da59535cfdf70c653654ecfad25d9882 Mon Sep 17 00:00:00 2001
From: Phil Pluckthun <phil@kitten.sh>
Date: Wed, 22 Apr 2026 09:07:11 +0100
Subject: [PATCH 6/6] Lazily compute ancestor of root idx

---
 packages/metro-file-map/src/lib/TreeFS.js | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/packages/metro-file-map/src/lib/TreeFS.js b/packages/metro-file-map/src/lib/TreeFS.js
index d8bd57f8ca..84523295ab 100644
--- a/packages/metro-file-map/src/lib/TreeFS.js
+++ b/packages/metro-file-map/src/lib/TreeFS.js
@@ -738,13 +738,13 @@ export default class TreeFS implements MutableFileSystem {
         // with the remaining path results in collapsing segments, e.g:
         // '../..' + 'parentofroot/root/foo.js' = 'foo.js', then we must add
         // parentofroot and root as ancestors.
-        ancestorOfRootIdx =
-          this.#pathUtils.getAncestorOfRootIdx(normalSymlinkTarget);
         if (
           collectAncestors &&
           !isLastSegment &&
           // No-op optimisation to bail out the common case of nothing to do.
-          (ancestorOfRootIdx === 0 || joinedResult.collapsedSegments > 0)
+          ((ancestorOfRootIdx =
+            this.#pathUtils.getAncestorOfRootIdx(normalSymlinkTarget)) === 0 ||
+            joinedResult.collapsedSegments > 0)
         ) {
           let node: MixedNode = this.#rootNode;
           let collapsedPath = '';