When includePatchedDependencies is enabled, copy relevant patch files from the workspace root to the isolated directory and update the isolated package.json with patch references.

Patches are filtered based on the target package's dependencies:

• Production dependency patches are always included
• Dev dependency patches are included only when includeDevDependencies is true
• Patches for packages not in the target's dependencies are excluded

The lockfile generator also filters patchedDependencies to match only relevant packages.

Based on #142 but adapted for the updated tooling (tsdown instead of tsup).

Subsequent improvements

After the initial implementation, several refinements were made to improve code quality, fix bugs, and ensure correctness:

Code organization

• Extracted shared utilities - The getPackageName function (which parses package specs like @firebase/[email protected] into package names) was duplicated between copy-patches.ts and filter-patched-dependencies.ts. Extracted to src/lib/utils/get-package-name.ts.

• Extracted filtering logic - The patch filtering logic was also duplicated. Extracted to src/lib/utils/filter-patched-dependencies.ts as a generic utility that works with any value type via TypeScript generics.

• Preserved folder structure - Patch files are copied preserving their original directory structure rather than flattening to a single patches/ directory.

Bug fixes

• Manifest consistency - The filtering was using the original targetPackageManifest instead of the adapted outputManifest. This could cause issues since the output manifest may have different dependency references. Fixed to use outputManifest for filtering.

• Lockfile patch paths - The lockfile was being generated before patches were copied, causing a mismatch between the paths in the lockfile and the actual copied files. Fixed by:

  1. Reordering operations so copyPatches runs before processLockfile
  2. Having copyPatches return the full PatchFile format (with path and hash)
  3. Reading hashes from the original lockfile so they're preserved after copying
  4. Passing pre-computed patched dependencies to the lockfile generator

Test coverage

Added comprehensive unit tests for the new utilities:

• get-package-name.test.ts - 14 tests covering scoped packages, edge cases, and malformed input
• filter-patched-dependencies.test.ts - 11 tests for filtering logic with various dependency configurations
• copy-patches.test.ts - 10 tests for the patch copying functionality

Type safety

• Defined a local PatchFile interface ({ path: string; hash: string }) matching the pnpm lockfile format, since the installed @pnpm/types version doesn't export this type
• Used TypeScript generics in filterPatchedDependencies<T> to preserve the value type through filtering operations