[iOS] Can't produce sourcemap with Hermes

[taltrui]

Hi! I can't produce a working sourcemap when building in iOS with Hermes activated.

I've created an issue in react native: react/react-native#32497 but I would like to know if someone from Rollbar has some insight in this or a workaround (or something I'm missing).

Thank you!

[waltjones]

Can you post what steps you're following to build your source map? Also, what is the error or problem you're seeing with the source map?

[taltrui]

Hi @waltjones ! Of course:

The sourcemap is generated in an XCode build phase, I've tried a few things:

Without Hermes:

export NODE_BINARY=node
export PROJECT_ROOT="${PROJECT_DIR}/../"
export EXTRA_PACKAGER_ARGS="--sourcemap-output sourcemap.ios.js --entry-file index.js --sourcemap-sources-root ./"

../../../node_modules/react-native/scripts/react-native-xcode.sh index.js

And then making the app crash yields this in Rollbar

If I activate Hermes and use the same method as above:

If I change the script to this:

export NODE_BINARY=node
export PROJECT_ROOT="${PROJECT_DIR}/../"
export SOURCEMAP_FILE="${PROJECT_DIR}/../sourcemap.ios.js"
export EXTRA_PACKAGER_ARGS="--entry-file index.js --sourcemap-sources-root ./"

../../../node_modules/react-native/scripts/react-native-xcode.sh index.js

Then the issue I created in react-native repo happens and no sourcemap is created.

[taltrui]

Hi @waltjones, I've tried creating the sourcemap manually for Hermes, like this:

yarn react-native bundle --platform ios --dev false --entry-file index.js --bundle-output main.jsbundle --sourcemap-output main.jsbundle.map --sourcemap-sources-root ./

ios/Pods/hermes-engine/destroot/bin/hermesc -O --emit-binary -output-source-map -out=main.jsbundle.hbc main.jsbundle

node ../../node_modules/react-native/scripts/compose-source-maps.js main.jsbundle.map main.jsbundle.hbc.map -o sourcemap.ios.js

Sourcemap is successfully created, and it seems that Rollbar can make "real" paths, but they are wrong:

As you can see in the image, the function name that makes the crash is indeed "crash", but the path "...src/app/screens/Accounts/components/SOSRecharge/index.js" is not the correct one. The correct one would be "...src/app/screens/Auth/flavours/common/index.js".