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fix(swc-plugin): rewrite anonymous export default class to const declaration - #1601
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…p/serde entries When node_modules packages include "sideEffects": false in their package.json, esbuild drops bare imports from the virtual-entry.js file. This is incorrect because the SWC compiler transform injects side-effectful registration code (workflow IDs, step IDs, class serialization) into these modules. Fix: return the resolved path alongside sideEffects: true from the onResolve handler so esbuild uses the plugin's resolution result instead of re-reading the package.json.
…mlink compatibility Extract withRealpaths() helper and use it for both normalizedEntriesToBundle and sideEffectEntries at all three bundle sites. This ensures the sideEffects override works correctly under pnpm/workspace symlinked layouts where enhanced-resolve may return realpaths that differ from the original discovered file paths.
🦋 Changeset detectedLatest commit: f0af6af The changes in this PR will be included in the next version bump. This PR includes changesets to release 17 packages
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🧪 E2E Test Results❌ Some tests failed Summary
❌ Failed Tests🌍 Community Worlds (59 failed)mongodb (2 failed):
redis (2 failed):
turso (55 failed):
Details by Category✅ ▲ Vercel Production
✅ 💻 Local Development
✅ 📦 Local Production
✅ 🐘 Local Postgres
✅ 🪟 Windows
❌ 🌍 Community Worlds
✅ 📋 Other
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Pull request overview
Updates the SWC workflow transform to ensure default-exported classes have a module-scope binding name when the plugin needs to emit registration code (serde and/or step/workflow method registrations), avoiding runtime ReferenceError for anonymous export default class { ... } patterns.
Changes:
- Add transformer logic to defer and rewrite anonymous default class exports into
const <name> = class <name> { ... }; export default <name>;. - Ensure named default class exports set the binding name so generated registration code consistently references the in-scope identifier.
- Add/extend fixtures and spec documentation describing the new rewriting behavior.
Reviewed changes
Copilot reviewed 11 out of 11 changed files in this pull request and generated 5 comments.
Show a summary per file
| File | Description |
|---|---|
| packages/swc-plugin-workflow/transform/src/lib.rs | Implements deferred rewrite for anonymous default class exports and binding-name tracking for default-exported classes. |
| packages/swc-plugin-workflow/spec.md | Documents anonymous default class export rewriting behavior and expected output. |
| .changeset/tall-owls-glow.md | Publishes a patch changeset describing the fix. |
| packages/swc-plugin-workflow/transform/tests/fixture/export-default-class-named/input.js | Adds fixture input for named export default class MyService { ... } with serde + step. |
| packages/swc-plugin-workflow/transform/tests/fixture/export-default-class-named/output-step.js | Expected step-mode output for named default class export. |
| packages/swc-plugin-workflow/transform/tests/fixture/export-default-class-named/output-workflow.js | Expected workflow-mode output for named default class export. |
| packages/swc-plugin-workflow/transform/tests/fixture/export-default-class-named/output-client.js | Expected client-mode output for named default class export. |
| packages/swc-plugin-workflow/transform/tests/fixture/export-default-class-anonymous/input.js | Adds fixture input for anonymous export default class { ... } with serde + step. |
| packages/swc-plugin-workflow/transform/tests/fixture/export-default-class-anonymous/output-step.js | Expected step-mode output showing const-decl rewrite and correct registrations. |
| packages/swc-plugin-workflow/transform/tests/fixture/export-default-class-anonymous/output-workflow.js | Expected workflow-mode output showing const-decl rewrite and correct registrations. |
| packages/swc-plugin-workflow/transform/tests/fixture/export-default-class-anonymous/output-client.js | Expected client-mode output showing const-decl rewrite and correct registrations. |
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Base automatically changed from
fix/class-expr-binding-name-method-registration to
mainApril 3, 2026 18:36
…s handling - Remove dead Expr::Class handler in visit_mut_export_default_expr (SWC wraps parenthesized form in Expr::Paren, so it never fires) - Extract class_needs_binding_rewrite() helper, eliminating duplicated detection logic and unnecessary body clones - Add debug_assert for mutual exclusivity of default_workflow_exports and default_class_exports - Clarify spec.md on self-name behavior difference between serde and step-only classes
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📊 Benchmark Results
workflow with no steps💻 Local Development
workflow with 1 step💻 Local Development
workflow with 10 sequential steps💻 Local Development
workflow with 25 sequential steps💻 Local Development
workflow with 50 sequential steps💻 Local Development
Promise.all with 10 concurrent steps💻 Local Development
Promise.all with 25 concurrent steps💻 Local Development
Promise.all with 50 concurrent steps💻 Local Development
Promise.race with 10 concurrent steps💻 Local Development
Promise.race with 25 concurrent steps💻 Local Development
Promise.race with 50 concurrent steps💻 Local Development
workflow with 10 sequential data payload steps (10KB)💻 Local Development
workflow with 25 sequential data payload steps (10KB)💻 Local Development
workflow with 50 sequential data payload steps (10KB)💻 Local Development
workflow with 10 concurrent data payload steps (10KB)💻 Local Development
workflow with 25 concurrent data payload steps (10KB)💻 Local Development
workflow with 50 concurrent data payload steps (10KB)💻 Local Development
Stream Benchmarks(includes TTFB metrics)workflow with stream💻 Local Development
stream pipeline with 5 transform steps (1MB)💻 Local Development
10 parallel streams (1MB each)💻 Local Development
fan-out fan-in 10 streams (1MB each)💻 Local Development
SummaryFastest Framework by WorldWinner determined by most benchmark wins
Fastest World by FrameworkWinner determined by most benchmark wins
Column Definitions
Worlds:
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Summary
ReferenceErrorwhenexport default class { ... }(anonymous) has serde or step methodsexport default class { ... }→const __defaultClass = class __defaultClass { ... }; export default __defaultClass;current_class_binding_namefor named default class exports (export default class Foo { ... }) so registration uses the class nameStacked on#1599
Details
When an anonymous class is exported as the default export:
The SWC plugin generates registration code at module scope that needs to reference the class by name (e.g.,
registerStepFunction("...", ClassName.prototype["process"])). Without a binding name, the fallback was"AnonymousClass"which doesn't exist as a variable — causing aReferenceErrorat runtime.Fix
Two changes in the SWC plugin:
visit_mut_export_default_decl(DefaultDecl::Class): Detects anonymous classes with serde/step methods, generates a unique name (__defaultClass), setscurrent_class_binding_name, and defers the rewrite tovisit_mut_module_items.visit_mut_export_default_expr(Expr::Class): Same logic for the expression form (e.g.,export default (class { ... })).visit_mut_module_items: Processes the deferred rewrites — removes the originalexport default, insertsconst __defaultClass = class __defaultClass { ... };, and re-exports withexport default __defaultClass;.Named default class exports (
export default class Foo { ... }) don't need rewriting —Foois already in scope. The fix just setscurrent_class_binding_nameso the transformer usesFooconsistently.Tests
6 new tests (2 fixtures × 3 modes):
export-default-class-anonymous: Anonymous default class with serde + step method → verifies rewrite toconst __defaultClass = class __defaultClass { ... }; export default __defaultClass;with correct registration codeexport-default-class-named: Named default class (export default class MyService { ... }) → verifies no rewrite needed,MyServiceused for all registrations144 total SWC tests pass (138 existing + 6 new).