Why will yarn install dev dependencies when I just need the builds?

Question

If I invoke yarn add <my-package>, Yarn will install both dependencies and devDependencies of <my-package>. Is it normal behavior ?

I checked the documentation but I couldn't find a way to prevent it from installing the development dependencies (which I don't need). I believe devDependencies are the dependencies that were used to compile the sources into the build scripts. And building my app I just need the builds.

Solution 1

Use --production=true (or simply --production or --prod for short). It is indeed normal behaviour; Yarn assumes you are in a 'development' context unless your NODE_ENV environment variable is set to 'production'.

Have a look at Yarn's documentation.

Solution 2

As said in the comment by @ddotsenko

Not "broken" but "badly designed" --prod still downloads and "installs" dev packages IF yarn needs to resolve "full tree". Just use yarn install --production --frozen-lockfile and matching yarn.lock and --production will work as expected.

That worked to remove a 210 MB node_modules to 70 MB, similar to npm and pnpm.

Solution 3

NODE_ENV=production also prevent install devDependencies

Solution 4

Yarn has a --production option, which will cause it to install only production dependencies. This is shown here

View more solutions

Comments

[brodybits]

This functionality seems to be broken due to github.com/yarnpkg/yarn/issues/6323

[ddotsenko]

Not "broken" but "badly designed" --prod still downloads and "installs" dev packages IF yarn needs to resolve "full tree". Just use yarn install --production --frozen-lockfile and matching yarn.lock and --production will work as expected.

[serv-inc]

@ddotsenko : that is so helpful, it is now an answer . Please write your own for your well-deserved credit and @ notify me for mine to be deleted.

[akshat]

--production flag has been deprecated for yarn 2.0. How to prevent yarn 2.0 from installing dev dependencies?

[zyfyy]

use NODE_ENV=production as environments before excute yarn or yarn install

[tomdaly]

Late to the party but the new way to do this in Yarn 2+ is by using yarn workspaces focus --production --all: yarnpkg.com/cli/workspaces/focus

[Resisty]

Unfortunately I don't have an answer, but I'd like to note that none of the above is correct as of January 2022. Yarn will always install devDependencies regardless of options and NODE_ENV envvar.