Is there a Yarn equivalent for "npm dedupe"?

Question

Just tried out Yarn and indeed it's mega-fast. After running yarn in the console with a loaded package.json, it installed everything. I then ran npm dedupe expecting nothing much to happen since Yarn is so optimized, but it removed a ton of stuff. Is there some Yarn equivalent to npm dedupe?

Addition:

As noted in my comment below, I thought perhaps yarn install --flat might be an npm dedupe equivalent as the Yarn documentation describes it as "installing one and only one version of a package". So I played around with --flat and there's a couple things to note:

1. It will prompt you to choose what version of a package to install when the tree results in requests for more than one version. I could imagine this being one hell of a task for larger projects. I just picked the latest version for each package I was prompted for and as you can imagine, trying to run the app resulted in cannot find module errors.
2. I ran npm dedupe after doing a yarn install --flat and it still resulted in a ton of removals. This was a surprise to me.

So I'm taking it that npm dedupe is doing some other magic under the hood and I'm just naive about processes that I need not be concerned with. Perhaps it's just best to leave the tree alone and forget about --flat and dedupe altogether.

Answer 1

It seems like even now Yarn doesn't do the greatest job of minimizing duplicate dependencies. Running yarn --flat forces there to be only one version of a dependency even when they may not be compatible, so that's not ideal. You can use the yarn-deduplicate package to minimize the number of duplicates, while still allowing some in cases where there are not overlapping requirements. yarn-deduplicate also has a --fail option which will return a non-zero (failing) status. This can be useful to run on CI to ensure that anybody who modifies dependencies doesn't introduce new duplicates.