How do I force Yarn to reinstall a package?

You can use the yarn link command. This will set up your local dependency so that whenever you make a change on the dependency, it immediately shows up in your main project without you having to do anything else to update it.

If your main project is in ~/programming/main and your dependency is in ~/programming/dependency and is named MyLocalDependency, you will want to:

1) Run yarn link (with no additional flags) from within your dependency:

cd ~/programming/dependency
yarn link

2) Run yarn link <name of dependency package> from within your main project:

cd ~/programming/main
yarn link MyLocalDependency

And you're done!

If you want to switch from a local copy of the dependency to one hosted elsewhere, you can use yarn unlink.

cd ~/programming/main
yarn unlink MyLocalDependency
cd ~/programming/dependency
yarn unlink

---

If you're using NPM instead of Yarn, npm link and npm link <dependency> work in effectively the same way. To unlink the dependency, run npm rm --global <dependency>. (This is because npm link works by creating a simlink in the global NPM set of packages, so uninstalling the linked dependency from the global packages also breaks the link.)

See the npm link documentation and How do I uninstall a package installed using npm link?

Reinstalling a package after just deleting the node module works with:

yarn install --check-files

There is one other way. Just use yarn upgrade package-name

See manual: https://yarnpkg.com/lang/en/docs/cli/upgrade/