From 6656baaea32be196dd97b93a283a0e6d02b170ab Mon Sep 17 00:00:00 2001
From: Victor Sumner <308886+vsumner@users.noreply.github.com>
Date: Tue, 24 Mar 2026 21:12:00 -0400
Subject: [PATCH] fix(cafs): update locker cache when file exists with correct
 integrity (#11085)

* fix(cafs): update locker cache when file exists with correct integrity

The CAS locker cache was not updated when a file already existed on disk
with correct integrity. This caused repeated verifyFileIntegrity calls
on subsequent lookups within the same process, adding unnecessary I/O.

* fix(test): assert locker cache value not just key existence

Strengthen the test to verify locker.get() returns the correct
checkedAt timestamp, not just that the key exists.
---
 .changeset/fix-cafs-locker-cache.md       |  6 ++++++
 store/cafs/src/writeBufferToCafs.ts       |  4 +++-
 store/cafs/test/writeBufferToCafs.test.ts | 23 +++++++++++++++++++++++
 3 files changed, 32 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/fix-cafs-locker-cache.md

diff --git a/.changeset/fix-cafs-locker-cache.md b/.changeset/fix-cafs-locker-cache.md
new file mode 100644
index 0000000000..247f7caf97
--- /dev/null
+++ b/.changeset/fix-cafs-locker-cache.md
@@ -0,0 +1,6 @@
+---
+"@pnpm/store.cafs": patch
+"pnpm": patch
+---
+
+Fix a bug where the CAS locker cache was not updated when a file already existed with correct integrity, causing repeated integrity re-verification on subsequent lookups within the same process.
diff --git a/store/cafs/src/writeBufferToCafs.ts b/store/cafs/src/writeBufferToCafs.ts
index 1d9e557aeb..183731723f 100644
--- a/store/cafs/src/writeBufferToCafs.ts
+++ b/store/cafs/src/writeBufferToCafs.ts
@@ -29,8 +29,10 @@ export function writeBufferToCafs (
   // However, there is no way to find which package index file references
   // the given file. So we should revalidate the content of the file again.
   if (existsSame(fileDest, integrity)) {
+    const checkedAt = Date.now()
+    locker.set(fileDest, checkedAt)
     return {
-      checkedAt: Date.now(),
+      checkedAt,
       filePath: fileDest,
     }
   }
diff --git a/store/cafs/test/writeBufferToCafs.test.ts b/store/cafs/test/writeBufferToCafs.test.ts
index a85c8f3dee..af24a9fad3 100644
--- a/store/cafs/test/writeBufferToCafs.test.ts
+++ b/store/cafs/test/writeBufferToCafs.test.ts
@@ -17,4 +17,27 @@ describe('writeBufferToCafs', () => {
     writeBufferToCafs(new Map(), storeDir, buffer, fileDest, 420, { digest, algorithm: 'sha512' })
     expect(fs.readFileSync(fullFileDest, 'utf8')).toBe('abc')
   })
+
+  it('should populate the locker cache when a file already exists with correct integrity', () => {
+    const storeDir = temporaryDirectory()
+    const fileDest = 'abc'
+    const buffer = Buffer.from('abc')
+    const digest = crypto.hash('sha512', buffer, 'hex')
+    const integrity = { digest, algorithm: 'sha512' }
+    const locker = new Map<string, number>()
+
+    // First write creates the file
+    writeBufferToCafs(locker, storeDir, buffer, fileDest, 420, integrity)
+    // Clear the locker to simulate a fresh lookup
+    locker.clear()
+
+    // Second call should find the file on disk and cache it
+    const result = writeBufferToCafs(locker, storeDir, buffer, fileDest, 420, integrity)
+    const fullFileDest = path.join(storeDir, fileDest)
+    expect(locker.get(fullFileDest)).toBe(result.checkedAt)
+
+    // Third call should return from locker cache without hitting disk
+    const cached = writeBufferToCafs(locker, storeDir, buffer, fileDest, 420, integrity)
+    expect(cached.checkedAt).toBe(result.checkedAt)
+  })
 })