esm: implement import.meta.main

[Lordfirespeed]

Implements #57226

This PR supersedes #32223

Fixes: #57226

[nodejs-github-bot]

Review requested:

• @nodejs/loaders

[Lordfirespeed]

@ljharb I would appreciate your review on this r.e. performance - I am particularly concerned about my changes in lib/internal/modules/esm/translators.js, since I'm not familiar with implications of assignment to a JS object associated with a native object.

[codecov]

Codecov Report

Attention: Patch coverage is 97.87234% with 1 line in your changes missing coverage. Please review.

Project coverage is 90.20%. Comparing base (a36981a) to head (3f8416a).
Report is 11 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/internal/modules/esm/loader.js	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #57804      +/-   ##
==========================================
- Coverage   90.21%   90.20%   -0.02%     
==========================================
  Files         630      630              
  Lines      186391   186421      +30     
  Branches    36608    36614       +6     
==========================================
+ Hits       168161   168165       +4     
- Misses      11052    11069      +17     
- Partials     7178     7187       +9     

Files with missing lines	Coverage Δ
lib/internal/modules/esm/initialize_import_meta.js	100.00% <100.00%> (ø)
lib/internal/modules/esm/translators.js	91.59% <100.00%> (+0.01%)	⬆️
lib/internal/modules/esm/utils.js	98.94% <100.00%> (+0.02%)	⬆️
lib/internal/worker.js	99.82% <100.00%> (+<0.01%)	⬆️
lib/internal/modules/esm/loader.js	94.95% <80.00%> (-0.09%)	⬇️

... and 26 files with indirect coverage changes

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[Lordfirespeed]

@ljharb I've moved the assignment into compileSourceTextModule, but I'm a bit confused

I think I can see where the cache is populated, but not where it is hit in compileSourceTextModule (unless it's in CPP?)
That leads me to think the cache gets hit at some point before the standard moduleStrategy function is used, which would mean moving the assignment either has no effect or is detrimental.

What am I missing?

[Lordfirespeed]

I think CI should pass now. make -j$(nproc) test is passing locally.

[Lordfirespeed]

I checked locally, it seems the test no longer fails with unusual character names using a relative import path.

[mcollina]

lgtm

[github-actions]

The notable-change PRs with changes that should be highlighted in changelogs. label has been added by @mcollina.

Please suggest a text for the release notes if you'd like to include a more detailed summary, then proceed to update the PR description with the text or a link to the notable change suggested text comment. Otherwise, the commit will be placed in the Other Notable Changes section.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/66343/

[targos]

There's a test for import.meta.main === false, but not for true, I think?

[LiviaMedeiros]

There's a test for import.meta.main === false, but not for true, I think?

There is:

node/test/es-module/test-esm-import-meta-main.mjs

Line 4 in 37091e6

assert.strictEqual(import.meta.main, true);

But it would still be nice to cover more cases, e.g.:

• worker threads
• child process (exec, fork)
• --eval

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/66367/

[mcollina]

lgtm

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/66510/

[aduh95]

This should land after #58079