yarn-plugin-prune-prod

Remove devDependencies from .pnp.cjs and the cache folder in Yarn 3.

Intended to assist with building smaller, more stable docker images that are consistent between environments by leveraging Yarn's Zero Install feature.

Installation

yarn plugin import https://raw.githubusercontent.com/troncali/yarn-prune-prod/main/bundles/%40yarnpkg/plugin-prune-prod.js

Command

yarn prune-prod

How it works

This plugin is a tweaked implementation of the focus command from@yarnpkg/workspace-tools, which does not have an option to prune the cache.

This plugin is equivalent to the command yarn workspaces focus --all --production (omits devDependencies but installs all other dependencies for all workspaces).

The context of how this plugin is used will dictate what happens:

• If the plugin is used with an existing cache of all project dependencies, the "install" will use cached files (without fetching each dependency) and update .pnp.cjs to omit devDependencies, then prune the cache of devDependencies.

• If the plugin is used without a cache, it will freshly fetch all dependencies other than devDependenciesand populate .pnp.cjs to match.

• If the plugin is used where some dependencies exist in the cache and some do not, both of the above will apply accordingly.

The result is equivalent to yarn install --production in Yarn 1.

Dockerfile example

A full example is available here, with relevant parts pasted below.

# Reduce image bloat with a prebuild to gather production files and dependencies
FROM node:16.5-alpine AS prebuild
    WORKDIR /tmp
    COPY ./build ./build
    COPY [".pnp.cjs", ".yarnrc.yml", "package.json", "yarn.lock", "./"]
    COPY ./.yarn ./.yarn
    # ./.yarn/cache includes devDependencies, so use plugin to prune
    RUN yarn prune-prod

# Build the production image
FROM node:16.5-alpine AS production
	RUN mkdir -p /home/node/app/builds && chown -R node:node /home/node/app
	WORKDIR /home/node/app
	USER node
	# Leverage Yarn's Zero-Install feature for production files and dependencies
	COPY --chown=node:node --from=prebuild /tmp .
	EXPOSE ${BACKEND_PORT}
	# Require .pnp.cjs for Yarn PnP's dependency resolution
	CMD ["node", "-r", "./.pnp.cjs", "builds/backend/main.js"]

Credits

This plugin implements the PR proposed by yinzara.