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yarnpkg

How to install packages based on the lock-file with Yarn?


We use Yarn to install dependencies. The yarn-lock file is in the repo. If Compared to composer for php, I would expect that when I run yarn install, that the dependencies are installed based on the lock-file, and the lock file does not change.

With composer install for php, you install always the same version for each package on any environment. I don't see why yarn does not work in a similar way.

I think that with yarn install the lock gets updated too often and the file loses its point since it actually does not lock versions. Or am I using the wrong commands?


Solution

  • Yarn 1

    I think your best bet is using the --frozen-lockfile flag with yarn install.

    Docs:

    If you need reproducible dependencies, which is usually the case with the continuous integration systems, you should pass --frozen-lockfile flag.

    Also

    Don’t generate a yarn.lock lockfile and fail if an update is needed.


    Yarn2

    If using yarn2 (aka yarn berry) this flag is renamed to --immutable as of v2.0.0.

    From the docs...

    If the --immutable option is set (defaults to true on CI since v3.0.0), Yarn will abort with an error exit code if the lockfile was to be modified. For backward compatibility we offer an alias under the name of --frozen-lockfile, but it will be removed in a later release.


    This way if someone tries to push changes to package.json, say upgrade react from ^16.8.0 to ^16.10.0, without updating the yarn.lock file. Then it will error out in the CI like below.

    > yarn install --frozen-lockfile
    error Your lockfile needs to be updated, but yarn was run with `--frozen-lockfile`.
    

    To address your comment:

    I think that with yarn install the lock gets updated too often and the file loses its point since it actually does not lock versions. Or am I using the wrong commands?

    Yarn/npm is just doing what you tell it to. If you set the version in your package.json to "react": "16.8.0" it will never update the yarn.lock but when using any of the npm ranges like the Caret (i.e. "react": "^16.8.0"), yarn/npm will resolve to the highest/newest version that satisfies the range you specified. You have all the power!


    Update

    I found a small edge case. If you are running yarn add in your ci, such as for a ci only dependency, it will update the lock file and do an install for all dependencies. For example....

    # Add ci dep
    yarn add codecov
    
    # Install all deps from yarn.lock
    yarn install --frozen-lockfile
    

    This will not error like you might expect. Instead, add the --frozen-lockfile to yarn add command like this...

    # Add ci dep
    yarn add codecov --frozen-lockfile
    
    # Install all deps from yarn.lock
    yarn install --frozen-lockfile