semantic-release-monorepo

semantic-release-monorepo

Apply semantic-release's automatic publishing to a monorepo.

Why

The default configuration of semantic-release assumes a one-to-one relationship between a GitHub repository and an npm package.

This library allows using semantic-release with a single GitHub repository containing many npm packages.

How

Instead of attributing all commits to a single package, commits are assigned to packages based on the files that a commit touched.

If a commit touched a file in or below a package's root, it will be considered for that package's next release. A single commit can belong to multiple packages and may trigger the release of multiple packages.

In order to avoid version collisions, generated git tags are namespaced using the given package's name: <package-name>-<version>.

Install

Both semantic-release and semantic-release-monorepo must be accessible in each monorepo package.

npm install -D semantic-release semantic-release-monorepo

Usage

Run semantic-release in the root of a monorepo package and apply semantic-release-monorepo via the extends option.

On the command line:

$ npm run semantic-release -e semantic-release-monorepo

Or in the release config:

{
  "extends": "semantic-release-monorepo"
}

NOTE: This library CAN'T be applied via the plugins option.

{
  "plugins": [
    "semantic-release-monorepo" // This WON'T work
  ]
}

With Lerna

The monorepo management tool lerna can be used to run semantic-release-monorepo across all packages in a monorepo with a single command:

lerna exec --concurrency 1 -- npx --no-install semantic-release -e semantic-release-monorepo

Thanks to how npx's package resolution works, if the repository root is in $PATH (typically true on CI), semantic-release and semantic-release-monorepo can be installed once in the repo root instead of in each individual package, likely saving both time and disk space.

Advanced

This library modifies the context object passed to semantic-release plugins in the following way to make them compatible with a monorepo.

Step	Description
analyzeCommits	Filters context.commits to only include the given monorepo package's commits.
generateNotes	Filters context.commits to only include the given monorepo package's commits. Modifies context.nextRelease.version to use the monorepo git tag format. The wrapped (default) generateNotes implementation uses this variable as the header for the release notes. Since all release notes end up in the same Github repository, using just the version as a header introduces ambiguity.

tagFormat

Pre-configures the tagFormat option to use the monorepo git tag format.

If you are using Lerna, you can customize the format using the following command:

"semantic-release": "lerna exec --concurrency 1 -- semantic-release -e semantic-release-monorepo --tag-format='${LERNA_PACKAGE_NAME}-v\\${version}'"

Where '${LERNA_PACKAGE_NAME}-v\\${version}' is the string you want to customize. By default it will be <PACKAGE_NAME>-v<VERSION> (e.g. foobar-v1.2.3).