Zoltan KochanandClaude Opus 5.5 2b964efd97 fix(peers): keep a rejected optional peer unbound through dedupePeerDependents (#17787)
When every candidate for a missing optional peer is rejected, the project
leaves the peer unbound. dedupePeerDependents then collapsed the project's
variant of the declaring package into another project's variant that
resolves the peer, handing the rejected peer (and its required peers)
back to the project.

The optional-peer hoist now records, per importer, the names it rejected.
Before the dedupe passes, every variant in that importer's closure that
leaves one of those optional peers unbound is listed, and the
compatibility check refuses to collapse a listed variant into one that
resolves the peer. A variant that absorbs a listed one inherits its
entry, and injected-dependency dedupe uses the same check. Implemented
in both the TypeScript resolver and pacquet.

Closes https://github.com/pnpm/pnpm/issues/17781

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
2026-11-06 17:19:30 +01:00
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pnpm

Fast, disk space efficient package manager:

  • Fast. Up to 2x faster than the alternatives (see benchmark).
  • Efficient. Files inside node_modules are linked from a single content-addressable storage.
  • Great for monorepos.
  • Strict. A package can access only dependencies that are specified in its package.json.
  • Deterministic. Has a lockfile called pnpm-lock.yaml.
  • Works as a Node.js version manager. See pnpm runtime.
  • Works everywhere. Supports Windows, Linux, and macOS.
  • Battle-tested. Used in production by teams of all sizes since 2016.
  • Experimental Rust port. Includes pacquet, an experimental port of the CLI written in Rust.
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Background

pnpm uses a content-addressable filesystem to store all files from all module directories on a disk. When using npm, if you have 100 projects using lodash, you will have 100 copies of lodash on disk. With pnpm, lodash will be stored in a content-addressable storage, so:

  1. If you depend on different versions of lodash, only the files that differ are added to the store. If lodash has 100 files, and a new version has a change only in one of those files, pnpm update will only add 1 new file to the storage.
  2. All the files are saved in a single place on the disk. When packages are installed, their files are linked from that single place consuming no additional disk space. Linking is performed using either hard-links or reflinks (copy-on-write).

As a result, you save gigabytes of space on your disk and you have a lot faster installations. If you'd like more details about the unique node_modules structure that pnpm creates and why it works fine with the Node.js ecosystem, read this small article: Flat node_modules is not the only way.

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Getting Started

Benchmark

pnpm is up to 2x faster than npm and Yarn classic. See all benchmarks.

Benchmarks on an app with lots of dependencies:

License

MIT, except the pnpr/ directory, which is source-available under the PolyForm Shield License 1.0.0.

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