feat(config): support typescript configs

[Titozzz]

Summary

Allowing the user to user ts config will reduce configuration mistakes

I had to revert 05b9ed4 as jiti uses os.tmpdir and it would conflict. But it seems to be running fine with node 18/20 at least

Test plan

Unsure how to test this, but the code seems pretty straightforward
Happy to discuss if testing is needed

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.45%. Comparing base (9151a87) to head (cb56c63).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1233   +/-   ##
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  Coverage   83.45%   83.45%           
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  Files         207      207           
  Lines       10712    10713    +1     
  Branches     2669     2669           
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+ Hits         8940     8941    +1     
  Misses       1772     1772           

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[robhogan]

Thanks for this, this would be a nice feature.

I do have some concerns about the dependency on jiti here - it's a very oddly assembled package that claims zero dependencies, but actually bundles (some version of) Babel as a 1.6MB file, discarding its licence in the process: https://unpkg.com/browse/jiti@1.21.0/dist/ .

That, and the fact that it's modifying the environment enough to break tests in weird ways, means we really can't accept a dependency on it.

As a possible alternative, transforming files is somewhat within Metro's wheelhouse - we obviously already have a dependency on Babel - and based on https://github.com/Codex-/cosmiconfig-typescript-loader/blob/main/lib/loader.ts it looks like implementing a loader is pretty straightforward - if it's only a few lines (plus tests), and a Babel plugin to roll our own, that might be the best option.

Aside: We're planning to update cosmiconfig for ESM support but are currently blocked by a Node<20 bug, details: react-native-community/cli#2167 (comment)

Allowing the user to user ts config will reduce configuration mistakes

Curious what you mean by this - I can see that TS would be nicer both syntactically and for consistency, but TS should already be checking the JSDoc types in metro.config.js - it's a template bug if not. Was it not working for you?

[robhogan]

Good catch - we should land this docs fix regardless.