esm: unflag --experimental-wasm-modules

[guybedford]

This unflags --experimental-wasm-modules for Node.js 24, while keeping the implementation experimental under 2.1 active development.

Source phase imports and string builtins as stable proposals are both promoted to 2.2 release candidate experimental status. The warning for importing Wasm modules is moved to only apply when importing module instances, rather than module sources as well.

With #56919 landed, Node.js supports both source phase imports and instance phase imports to WebAssembly modules and for Wasm imports to JS, in line with the current Phase 3 WebAssembly ESM Integration proposal (https://github.com/webassembly/esm-integration).

Recent additions to the source phase integration here also include:

• esm: WebAssembly.Global unwrapping for Wasm Namespaces #57525
• esm: top-level Wasm without package type #57610
• esm: add support for dynamic source phase hook #58147
• esm: add JS string builtins support to Wasm ESM Integration #59020

By unflagging, this will enable build tools to target source phase imports for Node.js as an output format, providing immediate benefit to Wasm consumers in enabling more seamless interoperability between JS and Wasm modules.

[nodejs-github-bot]

Review requested:

• @nodejs/loaders

[guybedford]

//cc @nodejs/loaders

[marco-ippolito]

So I assume its semver major?

[guybedford]

Strictly speaking, this isn't semver major since it has no breaking semantics. But, we only have fully V8 support on 24 unless there is a backport of the V8 update.

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 90.05%. Comparing base (c8d5b39) to head (483c78c).
Report is 20 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/internal/modules/esm/formats.js	50.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #57038      +/-   ##
==========================================
+ Coverage   90.03%   90.05%   +0.02%     
==========================================
  Files         648      648              
  Lines      190967   190978      +11     
  Branches    37425    37433       +8     
==========================================
+ Hits       171931   171987      +56     
+ Misses      11665    11607      -58     
- Partials     7371     7384      +13     

Files with missing lines	Coverage Δ
lib/internal/modules/esm/translators.js	92.45% <100.00%> (-0.02%)	⬇️
src/node.cc	74.72% <100.00%> (-0.07%)	⬇️
src/node_options.cc	84.49% <100.00%> (-0.12%)	⬇️
src/node_options.h	97.87% <ø> (-0.02%)	⬇️
lib/internal/modules/esm/formats.js	98.57% <50.00%> (-0.10%)	⬇️

... and 43 files with indirect coverage changes

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[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.

[guybedford]

I've also added a commit here to remove the experimental warning, given we are on a stabilization path for this feature, but for those who have already approved feel free to comment further - @mcollina @anonrig.

[guybedford]

Thanks for all the approvals it is great to see the interest in this.

After further discussion, since this is still a Phase 3 Wasm specification, that implies it is still in experimental implementation status until it reaches Phase 4.

While strictly speaking we can land experimental features unflagged in Node.js, the ESM Integraiton has already taken long enough that there is no need to rush something out the door here - so I will hold off on landing this for Node.js 24 and instead seek to land it for (hopefully) 25 instead where ideally we would be able to land under Phase 4 later in the year, or to then at least reconsider unflagging under Phase 3 if we feel it is in the interests of the project at that point for our users.

[marco-ippolito]

We discussed at the collab summit and we realized its not semver major so it can land

[guybedford]

Thanks for clarifying the case here, I'll aim to land this then when the current design discussions on the ESM Integration proposal repo have been resolved (theres a few final PRs in progress and under discussion right now - https://github.com/WebAssembly/esm-integration/pulls). Hopefully these should resolve fairly soon, but it may be more than a few weeks yet too.

[guybedford]

There is some relevant unflagging discussion in #57525 (comment).

I think the important thing for now is that given this is non-breaking that means we are able to backport the unflagging.

But we should not rush unflagging and try to reconcile with Chromium's shipping process here first as much as possible.

[guybedford]

I've made some final adjustments to this unflagging:

1. While the main Wasm integration remains 2.1 active development, source phase imports and string builtins as sub-features have are both marked in the docs as 2.2 release candidate (as Stage 3 at TC39 and Phase 4 Wasm stable specifications respectively).
2. The experimental warning for WebAssembly has been retained to only apply when importing WebAssembly in the instance phase, while source phase imports with string builtins do not get the warning in line with what Chrome is currently planning to ship.

This seems to me to strike the correct balance between communicating the correct experimental status and adoption.

[legendecas]

LGTM with one minor comment.

[anonrig]

Nice!

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/68124/

[guybedford]

Landed in 0df1518.