Support new babel feature allowing plugins to indicate external dependencies

Hey Kent, thanks for this awesome plugin, been using it for years and it’s really handy! Also saw you got in a car accident recently and I hope you’re not too beat up and recovering well.

I’ve been following this feature which just got merged to babel: https://github.com/babel/babel/pull/14065

I think that might be useful for this plugin to implement. It could allow us to invalidate the codegen output if the code has a dependency on some files on disk.

It seems pretty simple to utilize the new feature, if I’m right you just call api.addExternalDependency(external) where external is a filepath. https://github.com/babel/babel/pull/14065/files#diff-02893c5f57e6e79d081162d32cbfe84ccfac5ed70b8933be563e1dd7256f179cR15

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Here’s an example of a codegen module whose result depends on files on the filesystem, and could benefit from external dependency awareness:

// @codegen
const join = require('lodash/join')
const replace = require('lodash/replace')
const glob = require('glob')
const path = require('path')

const examplesFiles = glob.sync(path.resolve(__dirname, '**/examples.*'))

export default `export default {
  ${join(examplesFiles.map((exampleFile) => {
    const chopSrcFromPath = replace(exampleFile, /(.*):?src\//, '')
    return `'${chopSrcFromPath}': require('./${chopSrcFromPath}')`
  }), ',\n')}
}
/* 02-03-2022-09:22:00 */`

Right now we resort to updating the timestamp comment to force an invalidation + codegen rebuild. (Maybe there’s a better way that I don’t know about?)

I’m not sure the internals of this library but do you think it makes sense to implement? I might be able to take a stab at implementing it. Let me know if you have any pointers. Thanks!

[goatandsheep]

heads up: make sure you use 7.17.2 as there was a bug in 7.17.0

[TSMMark]

I tried implementing this but it seems like external dependencies must be added before the plugin is returned and registered to babel (e.g. right here: https://github.com/kentcdodds/babel-plugin-codegen/blob/5e8d0acfc255b801d9f3a57dbc46b05b8589d32d/src/index.ts#L14), and the cache.using entries can’t be added / updated dynamically after the plugin has been returned.

So that leads me to the assumption that this feature proposal will not be possible with the current version of the caching feature of babel… However, I’m hoping I’m wrong and that someone more familiar with babel core will prove me wrong eventually, or the babel caching will be updated to support dynamic cache deps.

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FTR The specific error is closely related to this open issue https://github.com/babel/babel/issues/14252

It seems like the babel cache/deps are intented only to be used for a static set of files, all of which are known at plugin definition time, and can not be dynamic, and can not be delayed until compile time.