pnpm Patches

pnpm's patching feature lets you modify third-party packages directly. Useful for applying fixes before upstream releases or customizing package behavior.

Creating a Patch

Step 1: Initialize Patch

pnpm patch <pkg>@<version>

# Example
pnpm patch [email protected]

This creates a temporary directory with the package source and outputs the path:

You can now edit the following folder: /tmp/abc123...

Step 2: Edit Files

Navigate to the temporary directory and make your changes:

cd /tmp/abc123...
# Edit files as needed

Step 3: Commit Patch

pnpm patch-commit <path-from-step-1>

# Example
pnpm patch-commit /tmp/abc123...

This creates a .patch file in patches/ and updates package.json:

patches/
└── [email protected]

{
  "pnpm": {
    "patchedDependencies": {
      "[email protected]": "patches/[email protected]"
    }
  }
}

Patch File Format

Patches use standard unified diff format:

diff --git a/lib/router/index.js b/lib/router/index.js
index abc123..def456 100644
--- a/lib/router/index.js
+++ b/lib/router/index.js
@@ -100,6 +100,7 @@ function createRouter() {
   // Original code
-  const timeout = 30000;
+  const timeout = 60000; // Extended timeout
   return router;
 }

Managing Patches

List Patched Packages

pnpm list --depth=0
# Shows (patched) marker for patched packages

Update a Patch

# Edit existing patch
pnpm patch [email protected]

# After editing
pnpm patch-commit <path>

Remove a Patch

pnpm patch-remove <pkg>@<version>

# Example  
pnpm patch-remove [email protected]

Or manually:

1. Delete the patch file from patches/
2. Remove entry from patchedDependencies in package.json
3. Run pnpm install

Patch Configuration

Custom Patches Directory

{
  "pnpm": {
    "patchedDependencies": {
      "[email protected]": "custom-patches/my-express-fix.patch"
    }
  }
}

Multiple Packages

{
  "pnpm": {
    "patchedDependencies": {
      "[email protected]": "patches/[email protected]",
      "[email protected]": "patches/[email protected]",
      "@types/[email protected]": "patches/@[email protected]"
    }
  }
}

Workspaces

Patches are shared across the workspace. Define in the root package.json:

// Root package.json
{
  "pnpm": {
    "patchedDependencies": {
      "[email protected]": "patches/[email protected]"
    }
  }
}

All workspace packages using [email protected] will have the patch applied.

Best Practices

1. Version specificity: Patches are tied to exact versions. Update patches when upgrading dependencies.

1. Document patches: Add comments explaining why the patch exists:

   # In patches/README.md
   ## [email protected]
   Fixes timeout issue. PR pending: https://github.com/expressjs/express/pull/1234

1. Minimize patches: Keep patches small and focused. Large patches are hard to maintain.

1. Track upstream: Note upstream issues/PRs so you can remove patches when fixed.

1. Test patches: Ensure patched code works correctly in your use case.

Troubleshooting

Patch fails to apply

ERR_PNPM_PATCH_FAILED  Cannot apply patch

The package version changed. Recreate the patch:

pnpm patch-remove [email protected]
pnpm patch [email protected]
# Reapply changes
pnpm patch-commit <path>

Patch not applied

Ensure:

1. Version in patchedDependencies matches installed version exactly
2. Run pnpm install after adding patch configuration

<!-- Source references:

• https://pnpm.io/cli/patch
• https://pnpm.io/cli/patch-commit
• https://pnpm.io/package_json#pnpmpatcheddependencies

-->