[BREAKING] feat: make resolver preset follow Metro defaults closely

[jbroma]

Summary

BREAKING CHANGE:

getResolveOptions is now way more compatible with metro-resolver and @react-native/metro-config

1. getResolveOptions now accepts a second optional parameter called options with the following properties:
   • enablePackageExports - defaults to false
   • preferNativePlatform - defaults to true
2. Order of extensions was changed to match the order from @react-native/metro-config.
3. Resolution via Package Exports (exports field in package.json) is now optional and disabled by default.
   It can now be enabled via getResolveOptions options parameter. This change was introduced to match metro defaults.
4. Default conditionNames are now: ['require', 'import', 'react-native'] and match @react-native/metro-config defaults.

Remarks

Implementation passes every metro-compat test with the following exceptions in package-exports-test:

• should resolve "exports" target directly > without expanding sourceExts - test should be marked as [nonstrict] as it relies on unsupported fallback mechanism
• should resolve "exports" target directly > without expanding platform-specific extensions - test should be marked as [nonstrict] as it relies on unsupported fallback mechanism
• subpath exports > should expand array of strings as subpath mapping (root shorthand) - this spec is not compliant with Node spec and should be fixed upstream as it's original purpose was to match Node spec.
• subpath patterns > should resolve subpath patterns in "exports" matching import specifier - one of the examples in the test is bad - Bar.js should not be exposed by the package according to the Node spec, but instead fallback to using less specific specifier. This mechanism is used to restrict imports in packages and should be fixed upstream

Checklist

• - rework implementation of getResolveOptions
• - adjust JSDoc
• - ensure TypeDoc compiles and displays new descriptions properly
• - add tests from Remarks to skipped ones

Test plan

• - pass selected metro-compat tests

[changeset-bot]

🦋 Changeset detected

Latest commit: 930a9a6

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@callstack/repack	Major
testerapp	Patch

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[thymikee]

What are possible migration paths, or differences in resolve behaviors that users could bump into unintentionally? This also shows some promise to remove now unnecessary webpack config overrides, can we provide some examples of what this means for the users in regards what can possibly change in their config?

[jbroma]

What are possible migration paths, or differences in resolve behaviours that users could bump into unintentionally?

The only real difference is that Package Exports support is now disabled by default. There might be packages out there that don't declare main field and only use exports field, but it's super rare (e.g. @react-native/dev-middleware). In this case this could be a breaking change. Until now users needed to override resolution via alias to get it to work (or disabling usage of package exports), or they relied on exports entrypoint.

This also shows some promise to remove now unnecessary webpack config overrides, can we provide some examples of what this means for the users in regards what can possibly change in their config?

We still need to override the webpack config defaults, nothing changes in this regard. The API of getResolveOptions is extended in a non-breaking way, with proper defaults in place 👍

[jbroma]

Order of extensions now matches @react-native/metro-config 1:1, updated PR description & changeset to reflect that, thanks @thymikee for spotting this 👍