pnpm/AGENTS.md

Agent Guide to pnpm Repository

This document provides context and instructions for AI agents working on the pnpm codebase.

The repository contains two stacks:

• The TypeScript pnpm CLI — everything outside pacquet/.
• The Rust pacquet port — pacquet/. See pacquet/AGENTS.md for pacquet-specific rules; it adds to (and never contradicts) the conventions below.

Sections below marked "(TypeScript only)" do not apply to pacquet. Everything else applies to both stacks.

Keep pnpm and pacquet in sync

The two stacks are parallel implementations of the same CLI — pacquet is a Rust port of pnpm whose behavior, flags, defaults, error codes, file formats, and lockfile shape are meant to match pnpm exactly. Any user-visible change has to land in both.

When you change one side, do the equivalent change on the other in the same PR if you can. If you can't (different expertise, scope too large, or pacquet hasn't ported the surrounding feature yet), open the PR with just your side — call out in the description what still needs porting, and someone else will push the matching commits to the same PR before it lands.

"User-visible" means anything that affects the CLI surface or the on-disk contract: command-line flags and defaults, environment-variable handling, lockfile/manifest/state-file format, error codes and messages, log emissions parsed by @pnpm/cli.default-reporter, store layout, hook semantics. Pure internal refactors, perf wins, and TS-only test cleanups don't need mirroring.

Scope caveat: pacquet currently only implements install. Resolution and every other command (update, add, remove, publish, exec, run, dlx, audit, etc.) live only in the TypeScript code, so changes there don't need a pacquet-side port yet — they're outside pacquet's current surface area. The parity rule will widen as pacquet ports more commands; check what pacquet exposes before deciding whether your change is in scope.

The pacquet-side obligation — pnpm is the source of truth, pacquet ports from it, never the other way around — is spelled out at pacquet/AGENTS.md.

Repository Structure

The pnpm codebase is a monorepo managed by pnpm itself. The root contains functional directories organized by domain:

Core Directories

• pnpm/: The CLI entry point and main package.
• pkg-manager/: Core package management logic (installation, linking, etc.).
• resolving/: Dependency resolution logic (resolvers for npm, tarballs, git, etc.).
• fetching/: Package fetching logic.
• store/: Store management logic (content-addressable storage).
• lockfile/: Lockfile handling, parsing, and utilities.

CLI & Configuration

• cli/: CLI command implementations and infrastructure.
• config/: Configuration management and parsing.
• hooks/: pnpm hooks (readPackage, etc.).
• completion/: Shell completion support.

Other Functional Directories

• network/: Network-related utilities (proxy, fetch, auth).
• workspace/: Workspace-related utilities.
• exec/: Execution-related commands (run, exec, dlx).
• env/: Node.js environment management.
• cache/: Cache-related commands and utilities.
• patching/: Package patching functionality.
• reviewing/: License and dependency review tools.
• releasing/: Release and publishing utilities.

Shared Utilities

• packages/: Shared utility packages (constants, error handling, logger, types, etc.).
• fs/: Filesystem utilities.
• crypto/: Cryptographic utilities.
• text/: Text processing utilities.

Rust Port

• pacquet/: The pnpm CLI ported to Rust. Self-contained sub-project with its own crates, tests, and tooling — see pacquet/AGENTS.md.

Setup & Build (TypeScript only)

To set up the environment and build the project:

pnpm install
pnpm run compile

To compile a specific package:

pnpm --filter <package_name> run compile

Important: The pnpm CLI e2e tests (in pnpm/test/) use the bundled pnpm/dist/pnpm.mjs, not the individual package lib/ outputs. After changing any package, you must rebuild the bundle before running e2e tests:

pnpm --filter pnpm run compile

This runs tsgo --build, linting, and pnpm run bundle (which bundles all packages into pnpm/dist/pnpm.mjs). Without this step, e2e tests will use a stale bundle and your changes won't be tested.

Testing (TypeScript only)

Never run all tests in the repository as it takes a lot of time.

Run tests for a specific project instead:

# From the project directory
pnpm test

# From the root, filtering by package name
pnpm --filter <package_name> test

Or better yet, run tests for a specific file:

pnpm --filter <package_name> test <file_path>

Or a specific test case in a specific file:

pnpm --filter <package_name> test <file_path> -t <test_name_pattern>

Linting (TypeScript only)

To run all linting checks:

pnpm run lint

Never ignore test failures

Do not dismiss a failing test as a "pre-existing" failure that is unrelated to your changes. Every test failure must be investigated and fixed. If a test was already broken before your changes, fix it as part of your work — do not silently skip it or treat it as acceptable.

Code Reuse and Avoiding Duplication

Before writing new code, always analyze the existing codebase for similar functionality. This is a large monorepo with many shared utilities — duplication is a real risk.

• Search before you write. Before implementing any non-trivial logic, search the codebase for existing functions, utilities, or patterns that do the same or similar thing. Check packages/, fs/, crypto/, text/, and other shared directories first.
• Extract shared code. If you find that the logic you need already exists in another package but is not exported or reusable, refactor it into a shared package rather than duplicating it. If you are adding new code that is similar to code that already exists elsewhere in the repo, move the common parts into a shared package that both locations can use.
• Prefer open source packages over custom implementations. Do not reimplement functionality that is already available as a well-maintained open source package. Use established libraries for common tasks (e.g., path manipulation, string utilities, data structures, schema validation). Only write custom code when no suitable package exists or when the existing packages are too heavy or unmaintained.
• Keep the dependency on the right level. When adding a new open source dependency, add it to the most specific package that needs it, not to the root or to a shared package unless multiple packages depend on it.

Commit Messages

Follow the Conventional Commits specification.

• feat: a new feature
• fix: a bug fix
• docs: documentation only changes
• style: formatting, missing semi-colons, etc.
• refactor: code change that neither fixes a bug nor adds a feature
• perf: a code change that improves performance
• test: adding missing tests
• chore: changes to build process or auxiliary tools

Changesets (TypeScript only)

If your changes affect published packages, you MUST create a changeset file in the .changeset directory. The changeset file should describe the change and specify the packages that are affected with the pending version bump types: patch, minor, or major.

IMPORTANT: Always explicitly include "pnpm" in the changeset with the appropriate version bump (patch, minor, or major). The pnpm CLI will only receive automatic patch bumps from its dependencies, so if your change warrants a minor or major version bump for the CLI, you must specify it explicitly. The changeset description will appear on the release notes page.

Example:

---
"@pnpm/installing.deps-installer": minor
"pnpm": minor
---

Added a new setting `blockExoticSubdeps` that prevents the resolution of exotic protocols in transitive dependencies [#10352](https://github.com/pnpm/pnpm/issues/10352).

Versioning Guidelines for pnpm CLI:

• patch: Bug fixes, internal refactors, and changes that don't require documentation updates
• minor: New features, settings, or commands that should be documented (anything users should know about)
• major: Breaking changes

Code Style (TypeScript only)

This repository uses Standard Style with a few modifications:

• Trailing commas are used.
• Functions are preferred over classes.
• Functions are declared after they are used (hoisting is relied upon).
• Functions should have no more than two or three arguments. If a function needs more parameters, use a single options object instead.
• Import Order:
  1. Standard libraries (e.g., fs, path).
  2. External dependencies (sorted alphabetically).
  3. Relative imports.

To ensure your code adheres to the style guide, run:

pnpm run lint

Common Gotchas

Error Type Checking in Jest (TypeScript only)

When checking if a caught error is an Error object, do not use instanceof Error. Jest runs tests in a VM context where instanceof checks can fail across realms.

Instead, use util.types.isNativeError():

import util from 'util'

try {
  // ... some operation
} catch (err: unknown) {
  // ❌ Wrong - may fail in Jest
  if (err instanceof Error && 'code' in err && err.code === 'ENOENT') {
    return null
  }
  
  // ✅ Correct - works across realms
  if (util.types.isNativeError(err) && 'code' in err && err.code === 'ENOENT') {
    return null
  }
  throw err
}

Working with GitHub PRs, Issues, and Comments

• Keep PR titles and descriptions current. When pushing new changes to a PR, review the title and description and update them if they no longer accurately reflect what the PR does.

• Reply to and resolve review conversations. Once a review comment has been addressed, reply to the thread with a description of the resolution including the commit hash that fixed it, then mark the conversation as resolved.

• Sign all agent-authored content. When posting a comment, creating an issue, or opening a PR, append a footer to the message indicating that it was written by an agent. The footer must include the name of the agent and the name of the model used. Example:

  ---
  Written by an agent (Claude Code, claude-opus-4-7).
  

Resolving Conflicts in GitHub PRs

Use shell/resolve-pr-conflicts.sh to resolve PR conflicts:

./shell/resolve-pr-conflicts.sh <PR_NUMBER>

The script force-fetches the base branch (avoiding stale refs), rebases, auto-resolves pnpm-lock.yaml conflicts via pnpm install, force-pushes, and verifies GitHub sees the PR as mergeable. For non-lockfile conflicts it will pause and list the files that need manual resolution.

Key Configuration Files

• pnpm-workspace.yaml: Defines the workspace structure.
• package.json (root): Root scripts and devDependencies.
• CONTRIBUTING.md: Detailed contribution guidelines.