Allow specifying jest's `cacheDirectory`

Hi, this proposal is related to issue https://github.com/facebook/jest/issues/3705 (jest cache is not handled correctly upon moving files from point A to point B. This eventually causes coverage information to be displayed incorrectly).

For this reason, it would be nice to have a way to clear the jest cache manually when required. In order to do that, it would be useful to have a way to set the cache directory.

This is possible in Jest by setting the cacheDirectory config option in package.json (or from the command line). Unfortunately, in an application created with create-react-app, this config option is among those which cannot be overridden:

Out of the box, Create React App only supports overriding these Jest options:

  • collectCoverageFrom
  • coverageReporters
  • coverageThreshold
  • snapshotSerializers.

These options in your package.json Jest configuration are not currently supported by Create React App:

  • cacheDirectory

Without being able to set cacheDirectory, the cache files are created in a random-looking temporary directory such as /private/var/folders/zj/112vf5bj0js_hx6l9ntz3w780000gn/T/jest_dx (at least on my Mac Os X Sierra machine).

I think it would be useful to be able to set cacheDirectory to something more predictable, such as ./node_modules/.cache/jest, or even ./.cache/jest.

What do you think?

Thanks in advance for this awesome tool!

[cpojer]

Watchman picks it up, it has to be ignored globally, I managed to publish some private cache to npm at some point, all these kinda things. Since we moved it to tmp, we didn’t have a problem with it at FB.

[gaearon]

We already store Babel cache in node_modules/.cache so we might as well do the same for Jest. But I’d love to learn more about:

We used to store it inside of Jest but it was always a huge issue to people

Can you research why it was an issue before? cc @cpojer