Pass unstable_transformProfile through Babel caller API and fall back to it in @react-native/babel-preset
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…back to it in `@react-native/babel-preset` Summary: `unstable_transformProfile` is used by Metro to hint at the appropriate set of Babel transforms for the target engine. To be effective in `react-native/babel-preset`, it must currently be passed in the preset config. When the user does not use a custom Babel config, `react-native/metro-babel-transformer` detects that and auto-configures the preset with options from Metro - that's fine. But if the user has their own Babel config, building on top of `react-native/babel-preset`, the preset for the config is fixed - so `unstable_transformProfile` has no effect. Ideally, `unstable_transformProfile` should be a function of the target engine - it's totally reasonable for one instance of Metro to build for multiple engines - so this should instead be passed programmatically to the engine by Metro for each transform job. Babel provides a mechanism to do this efficiently, without reinitialising the preset unnecessarily, via the `caller` API. This passes `unstable_transformProfile` through `caller`. Changelog: [Internal] (This is part of using a more optimised transform profiles for Hermes V1, which is still an experimental opt-in. When we stabilise Hermes V1 in RN, we should stabilise this API) Differential Revision: D82625477
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Summary:
unstable_transformProfileis used by Metro to hint at the appropriate set of Babel transforms for the target engine.To be effective in
react-native/babel-preset, it must currently be passed in the preset config.When the user does not use a custom Babel config,
react-native/metro-babel-transformerdetects that and auto-configures the preset with options from Metro - that's fine.But if the user has their own Babel config, building on top of
react-native/babel-preset, the preset for the config is fixed - sounstable_transformProfilehas no effect.Ideally,
unstable_transformProfileshould be a function of the target engine - it's totally reasonable for one instance of Metro to build for multiple engines - so this should instead be passed programmatically to the engine by Metro for each transform job.Babel provides a mechanism to do this efficiently, without reinitialising the preset unnecessarily, via the
callerAPI.This passes
unstable_transformProfilethroughcaller.Changelog: [Internal]
(This is part of using a more optimised transform profiles for Hermes V1, which is still an experimental opt-in. When we stabilise Hermes V1 in RN, we should stabilise this API)
Differential Revision: D82625477