Issue a warning if we detect a .js/.ts file collision

[dfreeman]

This PR will cause a warning to be emitted if we detect the situation described in #780. Because of exactly the situation we're detecting, we can't tell where the two conflicting files are coming from, but in most cases it will be apparent from context (e.g. the host app overriding a service from a particular addon).

Trying to describe the full situation and its possible ramifications would produce a giant wall of text in the terminal output, but the link in the warning points to #780, which has some good context and also links out to additional issues, like the upstream one in broccoli-persistent-filter.

[lifeart]

also issue happens if both files is .ts

way to escape issue:

• both files is .js
• one file with any extension

[dfreeman]

also issue happens if both files is .ts

I don't think this is correct. Addons should never have .ts files in their app/ trees, but if they do and the host also has a .ts file, it will override the addon's file.

[lifeart]

#724

[dfreeman]

Nothing in that thread indicates an issue when there were two conflicting .ts files when there wasn’t also a .js file of the same name floating around (e.g. because of differing addon versions that switched from including a .ts file to including a .js one)

If you can provide a reproduction where a nondeterministic build results from only .ts files I’m happy to take a look, but if you consider the underlying problem here, that can’t be caused by the same root issue as the one this PR is detecting, so it would need to be investigated and remedied separately.

[chriskrycho]

Looks good overall. Had one question just for my own understanding!

[lolmaus]

Just tried it and it detected collisions:

WARNING: Detected collisions between .js and .ts files of the same name. This can result in nondeterministic build output; see https://git.io/JvIwo for more information.
  - uni-frontend/middleware/index.{js,ts}
  - uni-frontend/models/saved-configuration.{js,ts}
  - uni-frontend/reducers/index.{js,ts}

This is awesome, thank you so much!!

[jamescdavis]

💯

[jamescdavis]

This has been released in v3.1.3.

[azhiv]

Can this warning be treated as an error during build? It would be nice to fail the build in case of a collision because otherwise proceeding with the collision (if missed) may result in significant harm.