`@react-native/metro-config` doesn't export default `assetExts` and `sourceExts` anymore.

[gvarandas]

Description

While upgrading to 0.72.0, we've noticed that the default config exported by @react-native/metro-config doesn't contain default values for the assetExts and sourceExts options, making it harder to extend those values in case projects need to perform any custom configuration.

A common use-case for extending these configs would be to better support svg files to be transpiled as React components (think of react-native-svg).

const { resolver: {sourceExts, assetExts} } = await getDefaultConfig();
// ...
resolver: {
  assetExts: assetExts.filter(ext => ext !== 'svg'),
  sourceExts: [...sourceExts, 'svg', 'cjs', 'mjs'],
},

It seems like this regression was caused due to dropping merging the original Metro config with the RN one (on this commit).

Is this a legit regression or do we expect projects to tap into metro-config directly to read those default values (maybe via loadConfig)?

Happy to provide a PR fixing the issue if it's flagged as a unintended behaviour.

React Native Version

0.72.0

Output of npx react-native info

  OS: macOS 13.4
  CPU: (8) arm64 Apple M1 Pro
  Memory: 115.80 MB / 16.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 20.3.1
    path: /opt/homebrew/bin/node
  Yarn:
    version: 1.22.19
    path: /opt/homebrew/bin/yarn
  npm:
    version: 9.6.7
    path: /opt/homebrew/bin/npm
  Watchman:
    version: 2023.06.12.00
    path: /opt/homebrew/bin/watchman
Managers:
  CocoaPods:
    version: 1.11.3
    path: /Users/gvarandas/.gem/ruby/3.1.2/bin/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 22.4
      - iOS 16.4
      - macOS 13.3
      - tvOS 16.4
      - watchOS 9.4
  Android SDK:
    API Levels:
      - "24"
      - "25"
      - "26"
      - "28"
      - "29"
      - "30"
      - "31"
      - "32"
      - "33"
    Build Tools:
      - 29.0.2
      - 30.0.2
      - 30.0.3
      - 31.0.0
    System Images:
      - android-29 | Google APIs ARM 64 v8a
      - android-29 | Google APIs Intel x86 Atom
      - android-29 | Google APIs Intel x86 Atom_64
      - android-31 | Google APIs ARM 64 v8a
      - android-31 | Google APIs Intel x86_64 Atom
      - android-31 | Google Play ARM 64 v8a
      - android-33 | Google APIs ARM 64 v8a
    Android NDK: Not Found
IDEs:
  Android Studio: 2022.1 AI-221.6008.13.2211.9619390
  Xcode:
    version: 14.3/14E222b
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 11.0.15
    path: /usr/bin/javac
  Ruby:
    version: 3.1.2
    path: /opt/rubies/3.1.2/bin/ruby
npmPackages:
  "@react-native-community/cli": Not Found
  react:
    installed: 18.2.0
    wanted: 18.2.0
  react-native:
    installed: 0.72.0
    wanted: 0.72.0
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: false
iOS:
  hermesEnabled: true
  newArchEnabled: false

Steps to reproduce

• Install 0.72.0
• Install all dependencies (yarn, npm i, etc)
• Check that the output from getDefaultConfig (@react-native/metro-config) doesn't produce the following structure anymore:

resolver: {
  assetExts: [ /* values */],
  sourceExts [ /* values */],
},

Snack, code example, screenshot, or link to a repository

Any new project is capable of checking for this issue.
The code present in the Upgrade Helper would reproduce the issue consistently.

[abgaryanharutyun]

Hey @gvarandas this is not related to react native configuration just check this comment fromreact-native-svg-transformer
kristerkari/react-native-svg-transformer#276 (comment)

[cortinico]

cc @huntie

[huntie]

@react-native/metro-config is distinct from the metro-config package. Please see this answer: facebook/metro#1010 (comment).

Closing as duplicate.

[huntie]

This is being cherry picked into the upcoming React Native 0.72.1 release. Please make sure to upgrade @react-native/metro-config (to 0.72.1) in order to access resolver.sourceExts, resolver.assetExts.