Provide more descriptive error message when source file is not found

[gaearon]

I required wrong file by mistake and got this message:

The actual message was obscured in Xcode console:

Error: 
 stack: 
ModuleError@http://localhost:8081/Examples/Movies/MoviesApp.includeRequire.runModule.bundle:105:23
require@http://localhost:8081/Examples/Movies/MoviesApp.includeRequire.runModule.bundle:202:28
http://localhost:8081/Examples/Movies/MoviesApp.includeRequire.runModule.bundle:28141:33
require@http://localhost:8081/Examples/Movies/MoviesApp.includeRequire.runModule.bundle:243:30
http://localhost:8081/Examples/Movies/MoviesApp.includeRequire.runModule.bundle:27651:26
require@http://localhost:8081/Examples/Movies/MoviesApp.includeRequire.runModule.bundle:243:30
http://localhost:8081/Examples/Movies/MoviesApp.includeRequire.runModule.bundle:946:27
require@http://localhost:8081/Examples/Movies/MoviesApp.includeRequire.runModule.bundle:243:30
applyWithGuard@http://localhost:8081/Examples/Movies/MoviesApp.includeRequire.runModule.bundle:871:25
require@http://localhost:8081/Examples/Movies/MoviesApp.includeRequire.runModule.bundle:194:39
global code@http://localhost:8081/Examples/Movies/MoviesApp.includeRequire.runModule.bundle:28295:9
 URL: http://localhost:8081/Examples/Movies/MoviesApp.includeRequire.runModule.bundle
 line: 202
 message: Requiring unknown module "./test/actions/RepoActionCreators". It may not be loaded yet. Did you forget to run arc build?"

It would be nice to display the actual error.

[gaearon]

It looks like this message replaces the original message very quickly.

[nick]

I found this too. I ended up commenting out these lines as a short term fix:

https://github.com/facebook/react-native/blob/master/Libraries/Bundler/Bundler.js#L49-L52

[vjeux]

cc @amasad

[amasad]

@gaearon in this case what module where you requiring?

[amasad]

ok, it looks like you were requiring RepoActionCreators. Did that module ever exist and then was deleted?

The packager should definitely return an error and no code. But it also seems to be a bug that the error message has been replaced with a less useful one. cc @frantic

[gaearon]

ok, it looks like you were requiring RepoActionCreators. Did that module ever exist and then was deleted?

No, I mistyped the filename. When I fixed it, the error went away.
It's just unfortunate that the real error is always quickly replaced with a vague one.

In fact if you mistype a filename and keep pressing Cmd+R really really fast, that'll give you time to read the first actual error on the screen (before it gets replaced by the vague one).

[joeyyang]

Replacing one error message with another is also giving me issues -- I have an npm module that's failing to load and having all the error messages persist would be very helpful in attempting to debug. Let me know what other information I can provide!

[frantic]

@nicklockwood fixed this a while ago