[swc-plugin] Preserve imports referenced by hoisted nested steps#1944
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TooTallNate merged 3 commits intomainfrom May 5, 2026
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[swc-plugin] Preserve imports referenced by hoisted nested steps#1944TooTallNate merged 3 commits intomainfrom
TooTallNate merged 3 commits intomainfrom
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Dead-code elimination ran before nested step functions were hoisted out of workflow bodies, so imports referenced only by hoisted step bodies were incorrectly stripped from the step bundle, causing a ReferenceError at runtime. Move DCE to run after hoisting in visit_mut_program.
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🦋 Changeset detectedLatest commit: 9d132e5 The changes in this PR will be included in the next version bump. This PR includes changesets to release 19 packages
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LGTM. Verified it in the SWC playground.
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Pull request overview
This PR adjusts the SWC workflow transform so dead-code elimination runs after nested step hoisting, with the goal of preserving module imports that hoisted step bodies still reference in step-mode output.
Changes:
- Moves
remove_dead_codefromvisit_mut_module_itemsto the end ofvisit_mut_program. - Updates existing step-mode fixtures whose hoisted steps now correctly retain required imports.
- Adds a regression fixture covering nested steps that reference module-level imports.
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Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.
Show a summary per file
| File | Description |
|---|---|
packages/swc-plugin-workflow/transform/tests/fixture/nested-steps-in-object-constructor/output-step.js |
Updates expected step output to retain an import used by a hoisted nested step. |
packages/swc-plugin-workflow/transform/tests/fixture/nested-step-with-closure/output-step.js |
Updates expected step output to retain an import referenced from hoisted closure-based steps. |
packages/swc-plugin-workflow/transform/tests/fixture/nested-step-references-module-import/output-workflow.js |
Adds workflow-mode regression output for the new nested-import fixture. |
packages/swc-plugin-workflow/transform/tests/fixture/nested-step-references-module-import/output-step.js |
Adds step-mode regression output showing preserved imports for a hoisted nested step. |
packages/swc-plugin-workflow/transform/tests/fixture/nested-step-references-module-import/input.js |
Adds the new regression input covering nested step references to module imports. |
packages/swc-plugin-workflow/transform/tests/fixture/factory-with-step-method/output-step.js |
Updates expected step output to retain an import used by a hoisted step method. |
packages/swc-plugin-workflow/transform/src/lib.rs |
Defers dead-code elimination until after nested step hoisting completes. |
.changeset/preserve-imports-used-by-hoisted-steps.md |
Records the patch release note for the SWC plugin fix. |
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…nctions Anonymous steps nested inside callback properties of a non-exported workflow function were registered with an unnamespaced step ID in step mode while the workflow-mode proxy looked them up under the workflow function name, causing a runtime 'step not found' failure. Set current_workflow_function_name in visit_mut_fn_decl for non-exported workflow functions to match the behavior in visit_mut_export_decl. Also clarify the fixture comment to distinguish step-mode and workflow-mode behavior per reviewer feedback.
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Pull request overview
Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.
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…n shapes Extends the previous fix to cover all three non-exported workflow declaration forms (async function decl, const arrow, const fn-expr) by visiting the workflow body with workflow context before replacing it, and corrects the __internal_workflows manifest comment to report the same prefixed step IDs that are registered at runtime and looked up by the workflow-mode WORKFLOW_USE_STEP proxy. Adds a dedicated regression fixture covering all three shapes.
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* [swc-plugin] Preserve imports referenced by hoisted nested steps Dead-code elimination ran before nested step functions were hoisted out of workflow bodies, so imports referenced only by hoisted step bodies were incorrectly stripped from the step bundle, causing a ReferenceError at runtime. Move DCE to run after hoisting in visit_mut_program. * [swc-plugin] Namespace nested step IDs under non-exported workflow functions Anonymous steps nested inside callback properties of a non-exported workflow function were registered with an unnamespaced step ID in step mode while the workflow-mode proxy looked them up under the workflow function name, causing a runtime 'step not found' failure. Set current_workflow_function_name in visit_mut_fn_decl for non-exported workflow functions to match the behavior in visit_mut_export_decl. Also clarify the fixture comment to distinguish step-mode and workflow-mode behavior per reviewer feedback. * [swc-plugin] Namespace nested step IDs across all workflow declaration shapes Extends the previous fix to cover all three non-exported workflow declaration forms (async function decl, const arrow, const fn-expr) by visiting the workflow body with workflow context before replacing it, and corrects the __internal_workflows manifest comment to report the same prefixed step IDs that are registered at runtime and looked up by the workflow-mode WORKFLOW_USE_STEP proxy. Adds a dedicated regression fixture covering all three shapes. Signed-off-by: Nathan Rajlich <n@n8.io>
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Summary
Fixes a bug in the SWC plugin where step-mode bundles dropped module-level imports that were referenced by step functions hoisted out of workflow bodies, causing a
ReferenceErrorat runtime.Root Cause
Ordering bug in the transform pipeline:
StepTransform::visit_mut_module_itemsruns and, at the end, invokesremove_dead_code, which strips any import not referenced by current top-level code.StepTransform::visit_mut_programthen hoists nested step functions out of workflow bodies onto the module top level (e.g.var _anonymousStep0 = async (input) => db.query(input.query);).db, but the import was already deleted in step 1.This only affected steps nested inside workflow function bodies — top-level steps already worked because their bodies were inlined in
itemsbefore DCE ran. Three pre-existing fixtures (nested-step-with-closure,nested-steps-in-object-constructor,factory-with-step-method) had committed buggy outputs that this change corrects.For example, given:
The previous step-mode output omitted
import { db } from './db';while still emittingvar _anonymousStep0 = async (input) => db.query(input.query);.Fix
In
packages/swc-plugin-workflow/transform/src/lib.rs:remove_dead_codecall from the end ofvisit_mut_module_items.remove_dead_code(&mut module.body)call invisit_mut_program, after nested step hoisting completes (right before metadata-comment insertion).Verification
tests/fixture/nested-step-references-module-import/covering both kept-imports (used by hoisted step) and stripped-imports (truly unused, or only used by replaced workflow body).output-step.jsfiles updated to now correctly include the imports their hoisted steps reference.spec.mdalready documented the desired behavior — no spec change needed; this is purely an implementation conformance fix.