Intended behaviour for externalDependencies

[mischnic]

I want to add support for addExternalDependency to Parcel, but found out that the meaning of these dependency strings isn't really specified.

#14065 (comment):

@babel/core does not resolve external dependencies: they can be any string you want. This makes it possible, for example, to also store URLs or pointers to a virtual fs (as long as the caller knows how to handle them).

And the only tool I could find using this information was babel-cli, which does path.resolve(process.cwd(), x):

babel/packages/babel-cli/src/babel/watcher.ts

Lines 74 to 76 in 7d63d2f

	const absDependencies = new Set(
	Array.from(dependencies, dep => path.resolve(dep)),
	);

(Is anyone aware of any other tool reading externalDependencies?)

---

How should Parcel interpret these strings?

• For absolute paths, it's clear.
• For relative paths: what should they be relative to? To the babel config, to the JS file being processed, to some root directory (which I think babel-cli does)
• For anything else (though the line between "file that doesn't exist" and "not a filepath" isn't clear cut), I guess Parcel would ignore them.

This goes against the "any string you want" idea, but there has to be some agreement to be able to use plugins and runners interchangeably.

[JLHwung]

For relative paths: what should they be relative to?

Good question! I think process.cwd() is not a bad default. Another choice is to respect cwd provided in Babel options. @nicolo-ribaudo Any idea?

[liuxingbaoyu]

@goatandsheep Just a little curious, how is this problem bothering you? From my simple understanding, this seems to be an undefined behavior that may cause some temporary distress, but it doesn't seem to cause real blocking.

[goatandsheep]

Hi @liuxingbaoyu I'm not sure if it's this problem specifically, but my attempt to integrate addExternalDependency was unsuccessful at preventing caching of a non-js file that I attempted to add as an external dependency. When I tried api.cache.never, it caused an infinite loop, which was also wrong. I'm not sure if it's a path issue or not goatandsheep/react-native-dotenv#288

[liuxingbaoyu]

@goatandsheep Hi! Have you tried converting all relative paths to absolute paths? This should avoid the problem.

[goatandsheep]

I will try this and get back to you

[goatandsheep]

I added path.join to make them absolute paths and noticed something but the issue with the file caching remains. When I added path.join only to the addExternalDependency, it noticed the cache was not setup properly. When I added it to the cache.using the warning went away. So something is working with the addExternalDependency function. However the fact remains that when I update the file, the cache is not updating in my demo app