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A monorepo will often need to install NPM packages that provide tools such as shell commands. In most cases, these tooling dependencies can be declared as the devDependencies of some Rush project, and then they will be installed by rush install using its centralized shrinkwrap file (package manager lock file). However, sometimes such dependencies are needed in situations where rush install has not been invoked, or where rush install might fail if a person's unfinished work includes some package.json modifications. For these situations, Rush's autoinstallers feature provides an isolated mechanism for installing tooling dependencies.

An autoinstaller is defined as folder under common/autoinstallers/ with a package.json file and its own private shrinkwrap file. This folder is added to Git, but it is not a normal Rush project: It is not installed by rush install, nor does it contain any buildable source code for rush build. An autoinstaller is purely a container for installing NPM dependencies. Autoinstallers can be associated with Rush features such as custom commands or Rush plugins; when the associated feature is invoked, Rush will automatically install the dependencies.

When to use autoinstallers

If you're enabling a Rush plugin, you must configure an autoinstaller.

If you are creating a Rush custom command whose script needs NPM dependences, there are several possible approaches to consider:

  • rush install: Typically most dependencies in a Rush monorepo will get installed all together by rush install using the centralized shrinkwrap file. For most needs, this is the simplest approach and easiest to maintain. If some dependencies are irrelevant to a particular task, you can skip installing them by using project selection parameters such as rush install --to example-project.

  • install-run.js: The install-run.js script enables you to install NPM packages outside of rush install. This is useful for commands that run in contexts where rush install is not invoked at all, or where rush install may be broken. For example, a Git commit hook script gets run on branches where rush install might fail: developers often commit work in progress, or a Git rebase may introduce broken commits that get fixed up by a later commit.

  • autoinstallers: A limitation of install-run.js is that it only installs one NPM package. For example, if your custom command needs multiple packages (for example the pretty-quick driver, the prettier engine, and some Prettier plugins), you could add them to the package.json file of an autoinstaller. Autoinstallers typically have a small dependency tree and thus install much faster than rush install.

    Some potential downsides of autoinstallers: In situations that require multiple autoinstallers and/or rush install, the package manager will be invoked multiple times and may need to install the same dependency from different shrinkwrap files. This can be significantly slower than if rush install could install everything together using the centralized shrinkwrap file. Also, autoinstallers are not validated or updated by rush update, so they require extra maintenance for upgrades.

Creating an autoinstaller

  1. Use the rush init-autoinstaller command to create the folder:

    # This creates the common/autoinstallers/my-autoinstaller/package.json file
    rush init-autoinstaller --name my-autoinstaller
  2. Edit the my-autoinstaller/package.json file to add your dependencies.

  3. Run rush update-autoinstaller to update the shrinkwrap file. You should redo this step whenever you modify the package.json file.

    # Create or update common/autoinstallers/my-autoinstaller/pnpm-lock.yaml
    # This file should be committed and tracked by Git.
    rush update-autoinstaller --name my-autoinstaller
  4. Commit the updated files to git

    git add common/autoinstallers/my-autoinstaller/

    git commit -m "Updated autoinstaller"

To associate an autoinstaller with a custom command, specify its name in the autoinstallerName field in command-line.json.

To associate an autoinstaller with a Rush plugin, see the Creating Rush plugins documentation.

Maintaining an autoinstaller

  • To modify an autoinstaller, edit its package.json file.

    # This will also upgrade any indirect dependencies.
    rush update-autoinstaller --name my-autoinstaller

    # Commit the updated pnpm-lock.yaml
    git commit -m "Updated autoinstaller"
  • To delete the autoinstaller, simply delete its folder:

    rm -Rf common/autoinstallers/my-autoinstaller

    # Commit the changes to Git
    git add common/autoinstallers

    git commit -m "Deleted autoinstaller"

See also