Wrong source map is generated

We came from this discussion on react-native repo where @hramos recommend us to move the issue here: https://github.com/facebook/react-native/issues/6946

You can find all the detailed information in there. Tho, to summarize: the packager generates the sourcemap with wrong lines more times that I’d like to recon.

Problem is still raising in latests versions. Thank you 😃

[anandprabhu]

@rafeca and @sospedra Here is a simple test repository to reproduce the issue along with the steps i have followed. https://github.com/anandprabhu/HelloRN

[rafeca]

Hey @anandprabhu , I’ve spent some time debugging the issue. First of all, thanks for the test repository and the repro instructions, it makes it so much easier to debug these kind of issues 👍

After reproducing it, I think that the issue comes from React Native itself (not sure if it’s from some native layer of from the JS interpreter).

What makes me think that is that the first line that gets reported by pidcat is already wrong (before even being symbolicated using the sourcemaps):

onPress@303:987
...

To check that, you can open the actual minified bundle from android/app/build/intermediates/assets/release/index.android.bundle and go to line 303, column 987 and you’ll see that it does not point indeed to the place where the error is thrown.

From this point, metro sourcemaps are working fine, since they translate that position to its corresponding source position.

I think that with this additional information, the discussion can be moved back to https://github.com/facebook/react-native/issues/6946