Add pnpm support

[dr460nf1r3]

Thanks for contributing to the buildpack. To speed up the process of reviewing your pull request please provide us with:

• A short explanation of the proposed change: add the long overdue pnpm support

• An explanation of the use cases your change solves: adds support for a package manager which speeds up the build times by being much more efficient than npm or yarn 1. Since this is a massive improvement for time spend in CI (e.g. for lifecycle tests), it may decrease expenses for the same purpose. When switching a particular MTA app to use pnpm, it effectively cut build times in half for this one use case tested. This was requested here as well, and closed without reason: pnpm support #398

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• I have made this pull request to the master branch

• I have added an integration test

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• ✅ login: dr460nf1r3 / name: Nιƈσ 🐉🔥 (1e6d9db, 1f53aaa, 20e8e18, 3a39839)

[Copilot]

Pull request overview

Adds pnpm as a supported package manager in the Node.js buildpack, including dependency installation, caching behavior, and integration coverage.

Changes:

• Detect pnpm usage via pnpm-lock.yaml / pnpm-workspace.yaml and support engines.pnpm in package.json.
• Install pnpm (via npm) and run dependency builds using a new pnpm build path and cache directory (.pnpm-store).
• Add unit + integration tests and pnpm fixtures (simple app + workspace app) to validate behavior.

Reviewed changes

Copilot reviewed 26 out of 35 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/nodejs/supply/supply_test.go	Extends supplier unit tests for pnpm detection, engines parsing, pnpm install, caching, and build flow.
src/nodejs/supply/supply.go	Adds pnpm wiring to supplier (detection, install, build selection, dependency listing, cache handling).
src/nodejs/supply/mocks_test.go	Adds a PNPM mock to support new supplier tests.
src/nodejs/supply/cli/main.go	Wires the new pnpm implementation into the supply CLI.
src/nodejs/pnpm/pnpm.go	Introduces pnpm build implementation (pnpm config set store-dir, pnpm install).
src/nodejs/pnpm/pnpm_test.go	Adds unit tests for pnpm build behavior (store-dir, prod mode, offline vendored store).
src/nodejs/pnpm/pnpm_suite_test.go	Adds ginkgo suite for pnpm package tests.
src/nodejs/pnpm/mocks_test.go	Adds gomock for pnpm Command interface used by tests.
src/nodejs/package_json/package_json.go	Adds engines.pnpm parsing + logging.
src/nodejs/integration/init_test.go	Registers PNPM integration suite.
src/nodejs/integration/pnpm_test.go	Adds integration tests for pnpm “simple” and “workspaces” fixture deployments.
fixtures/pnpm/simple/package.json	Adds a pnpm-based fixture app (simple).
fixtures/pnpm/simple/pnpm-lock.yaml	Adds lockfile for simple pnpm fixture.
fixtures/pnpm/simple/server.js	Adds server for simple pnpm fixture.
fixtures/pnpm/workspaces/package.json	Adds a pnpm workspace fixture root package.json.
fixtures/pnpm/workspaces/pnpm-lock.yaml	Adds lockfile for pnpm workspace fixture.
fixtures/pnpm/workspaces/pnpm-workspace.yaml	Adds pnpm workspace definition.
fixtures/pnpm/workspaces/packages/sample-lib/package.json	Adds sample workspace library package metadata.
fixtures/pnpm/workspaces/packages/sample-lib/index.js	Adds sample workspace library code.
fixtures/pnpm/workspaces/packages/sample-app/package.json	Adds sample workspace app package metadata.
fixtures/pnpm/workspaces/packages/sample-app/index.js	Adds sample workspace app server code.
fixtures/pnpm/workspaces/packages/pkg-a/package.json	Adds workspace package A metadata.
fixtures/pnpm/workspaces/packages/pkg-a/server.js	Adds workspace package A server.
fixtures/pnpm/workspaces/packages/pkg-b/package.json	Adds workspace package B metadata.
fixtures/pnpm/workspaces/packages/pkg-b/index.js	Adds workspace package B code.
fixtures/pnpm/unmet/package.json	Adds pnpm unmet-deps fixture package.json.
fixtures/pnpm/unmet/pnpm-lock.yaml	Adds pnpm unmet-deps fixture lockfile.
fixtures/pnpm/dev_deps/package.json	Adds pnpm dev-deps fixture package.json.
fixtures/pnpm/dev_deps/pnpm-lock.yaml	Adds pnpm dev-deps fixture lockfile.
.gitignore	Ignores node_modules in the repo.

Files not reviewed (4)

• fixtures/pnpm/dev_deps/pnpm-lock.yaml: Language not supported
• fixtures/pnpm/simple/pnpm-lock.yaml: Language not supported
• fixtures/pnpm/unmet/pnpm-lock.yaml: Language not supported
• fixtures/pnpm/workspaces/pnpm-lock.yaml: Language not supported

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