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feat: inline const for default export#21189

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feat/inline-const-default-export
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feat: inline const for default export#21189
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feat/inline-const-default-export

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@hai-x

@hai-x hai-x commented Jun 15, 2026

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Summary

What kind of change does this PR introduce?

We already inlines named const exports (optimization.inlineExports) but explicitly skipped export default <const> (the template carried a "For now we don't set inlined value for export default expression" note). This makes a default export inlinable when its expression is a primitive constant.

Did you add tests for your changes?

Yes

Does this PR introduce a breaking change?

No

If relevant, what needs to be documented once your changes are merged or what have you already documented?

n/a

Use of AI

Yes

@changeset-bot

changeset-bot Bot commented Jun 15, 2026

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🦋 Changeset detected

Latest commit: cdb5dd9

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package
Name Type
webpack Minor

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Click here if you're a maintainer who wants to add another changeset to this PR

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Types Coverage

Coverage after merging feat/inline-const-default-export into main will be
99.33%
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@codecov

codecov Bot commented Jun 15, 2026

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Codecov Report

❌ Patch coverage is 12.50000% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 41.02%. Comparing base (877f3dc) to head (cdb5dd9).

Files with missing lines Patch % Lines
.../dependencies/HarmonyExportExpressionDependency.js 9.09% 10 Missing ⚠️
...ependencies/HarmonyExportDependencyParserPlugin.js 20.00% 4 Missing ⚠️

❌ Your patch check has failed because the patch coverage (12.50%) is below the target coverage (90.00%). You can increase the patch coverage or adjust the target coverage.

❗ There is a different number of reports uploaded between BASE (877f3dc) and HEAD (cdb5dd9). Click for more details.

HEAD has 24 uploads less than BASE
Flag BASE (877f3dc) HEAD (cdb5dd9)
html5lib 1 0
css-parsing 1 0
integration 20 0
test262 2 0
Additional details and impacted files
@@             Coverage Diff             @@
##             main   #21189       +/-   ##
===========================================
- Coverage   92.70%   41.02%   -51.68%     
===========================================
  Files         588      466      -122     
  Lines       64091    56072     -8019     
  Branches    17785    15654     -2131     
===========================================
- Hits        59416    23004    -36412     
- Misses       4675    33068    +28393     
Flag Coverage Δ
css-parsing ?
html5lib ?
integration ?
test262 ?
unit 41.02% <12.50%> (-0.01%) ⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

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@codspeed-hq

codspeed-hq Bot commented Jun 15, 2026

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Merging this PR will improve performance by ×2.6

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 4 improved benchmarks
✅ 140 untouched benchmarks

Performance Changes

Mode Benchmark BASE HEAD Efficiency
Memory benchmark "asset-modules-inline", scenario '{"name":"mode-development-rebuild","mode":"development","watch":true}' 1,296.8 KB 323.7 KB ×4
Memory benchmark "asset-modules-bytes", scenario '{"name":"mode-development-rebuild","mode":"development","watch":true}' 1,048.3 KB 319.7 KB ×3.3
Memory benchmark "css-modules", scenario '{"name":"mode-development-rebuild","mode":"development","watch":true}' 1,153.4 KB 409.6 KB ×2.8
Memory benchmark "wasm-modules-async", scenario '{"name":"mode-development-rebuild","mode":"development","watch":true}' 488.8 KB 392.4 KB +24.54%

Tip

Curious why this is faster? Comment @codspeedbot explain why this is faster on this PR, or directly use the CodSpeed MCP with your agent.


Comparing feat/inline-const-default-export (cdb5dd9) with main (877f3dc)

Open in CodSpeed

@neoncube2

neoncube2 commented Jun 15, 2026

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I'm excited for this! :D

(Although I suppose that Terser might already inline the default export)

@hai-x

hai-x commented Jun 18, 2026

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Let's merge #21199 first, and then come back to this.

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2 participants