fix(metro-resolver): package exports array root shorthand

[jbroma]

Summary

This PR deals with array root shorthand edge case from #1236

• - fixed array root shorthand spec in tests to match Node.js resolution algorithm
• - aligned implementation of package exports for array root shorthand
• - added extra [nonstrict] test case to highlight that non-declared paths from array should not work normally

Changelog: [Experimental] Fix package exports array root shorthand resolution to behave like node (edge case)

Test plan

• - all tests pass

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.58%. Comparing base (f8f7d55) to head (bab106d).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1238   +/-   ##
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  Coverage   83.58%   83.58%           
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  Files         207      207           
  Lines       10737    10737           
  Branches     2683     2684    +1     
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  Hits         8974     8974           
  Misses       1763     1763           

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[huntie]

Thanks! I'm still trying to find where the previous root shorthand behaviour was documented. Lining up with current Node makes sense 👍🏻

[facebook-github-bot]

@huntie has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

[robhogan]

Huge thanks for working on this @jbroma.

From my testing just now I think there may be a bit more to this though that explains why an array is useful. It seems Node takes the first entry satisfying the asserted conditions.

Eg, with:

{
	"name": "pkg",
	"exports": [{"custom": "./foo.js"}, {"import": "./bar.js"}, "./baz.js"]
}

 resolve-test  node --conditions=custom -p 'require.resolve("pkg")'
/Users/robhogan/workspace/resolve-test/node_modules/pkg/foo.js
 resolve-test  node --experimental-default-type=module -e 'console.log(import.meta.resolve("pkg"))'
file:///Users/robhogan/workspace/resolve-test/node_modules/pkg/bar.js
 resolve-test  node -p 'require.resolve("pkg")'
/Users/robhogan/workspace/resolve-test/node_modules/pkg/baz.js

So I think the approach here would be to normalise to the equivalent object form, which I think is..

{
  ".":  {
    "custom": "./foo.js",
    "import": "./bar.js",
    "default": "./baz.js"
  }
}

That needs a bit more verifcation against other resolvers though, and we might also want to consider nested arrays or more complex objects, although I think correctly dealing with the array of strings-or-flat-objects case would be a strict improvement on where we are.

[jbroma]

@robhogan oh I absolutely agree - there is more to this than what meets the eye :)

I think we should proceed with merging this edge case and handle other scenarios in separate issues / PR's.
The normalisation that you've provided seems like a good starting point to begin with. We can reuse the repro from the #1236 and just add more cases there.

Is there anything else that needs to be addressed in this PR? I see the FB internal job failed for some reason.