sourceMappingURL directive missing from JS bundle in 0.14-rc

[benvinegar]

When using the following command:

react-native bundle --entry-file index.ios.js --platform ios --bundle-output ios/main.jsbundle --sourcemap-output ios/index.ios.map

I notice that no //# sourceMappingURL=... is present on the final line of main.jsbundle. It used to be.

Are we expected to add this line ourselves (totally fine)? It's not clear to me if this should be happening automatically or not.

[mkonicek]

There were quite a few changes recently: https://github.com/facebook/react-native/blob/master/breaking-changes.md

Do source maps not work for you? Why do you need sourceMappingURL? It's possible the implementation changed.

cc @martinbigio

[benvinegar]

Why do you need sourceMappingURL?

sourceMappingURL is what signals to the browser, "yes there is an associated source map for this file at this URL".

There were quite a few changes recently: https://github.com/facebook/react-native/blob/master/breaking-changes.md

Up until react-native 0.13, this directive was always output with the result of the bundle operation. Now it isn't – and the change is not mentioned in the release notes. I just want to know if that was a conscious decision by the team, or a mistake.

Background: our tool, Sentry, does exception tracking for react-native apps. We use sourceMappingURL to figure out which source map belongs with the minified code that generates an exception.

Now, I can easily add this directive manually; again, I just want to know if this was a mistake or not.

[martinbigio]

Hmm I'll take a look. I don't think the sourceMappingURL should have get stripped out of the bundle. This is most likely a mistake. Thanks a lot for reporting it :)

[mkonicek]

@benvinegar Thanks for the explanation! Cool to know Sentry has React Native support!

[qbig]

Hi @martinbigio any update on this ? Would love to know more about how source map and error reporting works now with React Native and more than happy to add to docs afterwards

[qbig]

might already be closed with #3531 and #3527 ?

[mkonicek]

Thanks for the ping @qbig! I just checked with a new app created with React Native 0.18 and the last few lines of the bundle are:

module.exports=findDOMNode;
});
;require("InitializeJavaScriptAppEngine");
;require("ZeroFinal18/index.ios.js");
//# sourceMappingURL=ios/index.ios.map
__SSTOKENSTRING = "@generated SignedSource<<dacb8638976bee177a6e914111a9cf5c>>"; 

[mkonicek]

Closing as it's fixed.

[skevy]

For posterity, source maps weren't even being enabled by the CLI properly...hence no sourceMappingURL being added to the bundle. :)

I had fixed here: #5288

[qbig]

@mkonicek @skevy Awesome!

[benvinegar]

@mkonicek – why is __SSTOKENSTRING on the last line?

According to the spec, sourceMappingURL should be the last line.

Sentry happens to look at the last 5 lines, so this still works, but I'm nervous that this might get forgotten and a bunch of extra lines will get added to the end over time, pushing sourceMappingURL further up and out of range.