inconsistent arguments to "bundle" command between android and iOS build scripts

Description:

As of 0.61.5, the Android/Gradle react.gradle script calls react-native bundle with the --sourcemap-output argument. In other words, it includes building source maps by default. However, the iOS/Xcode equivalent does not. Would it be possible to add support for the latter to also pass the --sourcemap-output value by default?

I realize both include ways to pass “extra args” to the react native bundle call, but in our case, we have a whitespace character in our Xcode scheme names (an unintended effect of following the suggestion in the react-native-config approach), and there does not seem to be a way to properly escape it in the $EXTRA_PACKAGER_ARGS value so that the script will interpret it properly (here is an explanation of this issue).

Nevertheless, it seems prudent for both scripts to behave consistently when bundling the js code. (It seems the --sourcemap-output arg was added to the android script about six months ago.)

React Native version:

Run `react-native info` in your terminal and copy the results here.

    OS: macOS Mojave 10.14.6
    CPU: (8) x64 Intel(R) Core(TM) i7-4980HQ CPU @ 2.80GHz
    Memory: 209.79 MB / 16.00 GB
    Shell: 3.2.57 - /bin/bash
  Binaries:
    Node: 10.16.0 - ~/.nvm/versions/node/v10.16.0/bin/node
    Yarn: 1.17.3 - ~/.nvm/versions/node/v10.16.0/bin/yarn
    npm: 6.9.0 - ~/.nvm/versions/node/v10.16.0/bin/npm
    Watchman: 4.9.0 - /usr/local/bin/watchman
  SDKs:
    iOS SDK:
      Platforms: iOS 13.2, DriverKit 19.0, macOS 10.15, tvOS 13.2, watchOS 6.1
    Android SDK:
      API Levels: 23, 25, 26, 27, 28, 29
      Build Tools: 28.0.2, 28.0.3, 29.0.0
      System Images: android-27 | Google APIs Intel x86 Atom, android-27 | Google Play Intel x86 Atom, android-28 | Google APIs Intel x86 Atom, android-28 | Google Play Intel x86 Atom, android-29 | Google Play Intel x86 Atom
  IDEs:
    Android Studio: 3.5 AI-191.8026.42.35.6010548
    Xcode: 11.3/11C29 - /usr/bin/xcodebuild
  npmPackages:
    react: ^16.9.0 => 16.12.0 
    react-native: ^0.61.5 => 0.61.5 
  npmGlobalPackages:
    react-native-cli: 2.0.1
    react-native: 0.59.10

Steps To Reproduce

Provide a detailed list of steps that reproduce the issue.
Issues without reproduction steps or code are likely to stall.

1. Compile binary code on Android Studio/Gradle
2. Compile binary code on Xcode/xcodebuild
3. Examine the output, or add debugging output to the react.gradle or react-native-xcode.sh scripts to see how they invoke the react-native bundle command.

Expected Results

Expect both bundler commands to be consistent in the arguments passed to the bundler-- e.g. both should create source maps.

[hramos]

Thanks for catching this! Tagging as a “Good first issue” in case anyone wants to send a PR and add this to iOS.

[kwkr]

As it doesn’t seem to be actively worked on, I tried to come up with some solution to that. Could anyone give me feedback on my current changes? https://github.com/facebook/react-native/pull/30573