Backport #1944: [swc-plugin] Preserve imports referenced by hoisted nested steps

.changeset/preserve-imports-used-by-hoisted-steps.md

@@ -0,0 +1,9 @@
+---
+"@workflow/swc-plugin": patch
+---
+
+Fix three bugs affecting nested step functions that get hoisted out of an enclosing function (workflows in any declaration form, plus regular factory-style functions returning objects with step methods):
+
+1. Module-level imports referenced only by hoisted step bodies were stripped by dead-code elimination, causing a `ReferenceError` at runtime.
+2. The step ID generated for nested anonymous steps inside a non-exported workflow declared as `const foo = async () => {}` or `const foo = async function() {}` was not namespaced under the workflow name in step mode, so it did not match the ID looked up by the workflow-mode proxy and caused a runtime "step not found" failure. Steps inside `async function foo()` workflows were already namespaced correctly; this brings the const-arrow and const-fn-expression forms into agreement.
+3. The `__internal_workflows` manifest comment reported nested anonymous step IDs without the workflow-name prefix even though the runtime registration and proxy lookup used the prefixed form, so downstream tooling (e.g. builders consuming the manifest) saw the wrong step ID.

packages/swc-plugin-workflow/transform/tests/fixture/closure-new-expr-and-module-declarations/output-step.js

@@ -2,7 +2,7 @@ import { __private_getClosureVars, registerStepFunction } from "workflow/interna
 // https://github.com/vercel/workflow/issues/1365
 import { MockLanguageModelV3 } from 'ai/test';
 import { xai as xaiProvider } from '@ai-sdk/xai';
-/**__internal_workflows{"steps":{"input.js":{"_anonymousStep0":{"stepId":"step//./input//_anonymousStep0"},"_anonymousStep1":{"stepId":"step//./input//_anonymousStep1"},"_anonymousStep10":{"stepId":"step//./input//_anonymousStep10"},"_anonymousStep11":{"stepId":"step//./input//_anonymousStep11"},"_anonymousStep12":{"stepId":"step//./input//_anonymousStep12"},"_anonymousStep13":{"stepId":"step//./input//_anonymousStep13"},"_anonymousStep14":{"stepId":"step//./input//_anonymousStep14"},"_anonymousStep15":{"stepId":"step//./input//_anonymousStep15"},"_anonymousStep16":{"stepId":"step//./input//_anonymousStep16"},"_anonymousStep17":{"stepId":"step//./input//_anonymousStep17"},"_anonymousStep2":{"stepId":"step//./input//_anonymousStep2"},"_anonymousStep3":{"stepId":"step//./input//_anonymousStep3"},"_anonymousStep4":{"stepId":"step//./input//_anonymousStep4"},"_anonymousStep5":{"stepId":"step//./input//_anonymousStep5"},"_anonymousStep6":{"stepId":"step//./input//_anonymousStep6"},"_anonymousStep7":{"stepId":"step//./input//_anonymousStep7"},"_anonymousStep8":{"stepId":"step//./input//_anonymousStep8"},"_anonymousStep9":{"stepId":"step//./input//_anonymousStep9"}}}}*/;
+/**__internal_workflows{"steps":{"input.js":{"_anonymousStep0":{"stepId":"step//./input//mockModel/_anonymousStep0"},"_anonymousStep1":{"stepId":"step//./input//xai/_anonymousStep1"},"_anonymousStep10":{"stepId":"step//./input//withForIn/_anonymousStep10"},"_anonymousStep11":{"stepId":"step//./input//withDoWhile/_anonymousStep11"},"_anonymousStep12":{"stepId":"step//./input//withShorthandProps/_anonymousStep12"},"_anonymousStep13":{"stepId":"step//./input//withComputedKey/_anonymousStep13"},"_anonymousStep14":{"stepId":"step//./input//mockTextModel/_anonymousStep14"},"_anonymousStep15":{"stepId":"step//./input//withClassExpr/_anonymousStep15"},"_anonymousStep16":{"stepId":"step//./input//withClassSuper/_anonymousStep16"},"_anonymousStep17":{"stepId":"step//./input//withClassProp/_anonymousStep17"},"_anonymousStep2":{"stepId":"step//./input//mockModelWrapped/_anonymousStep2"},"_anonymousStep3":{"stepId":"step//./input//configuredStep/_anonymousStep3"},"_anonymousStep4":{"stepId":"step//./input//withOptionalChaining/_anonymousStep4"},"_anonymousStep5":{"stepId":"step//./input//withSequenceExpr/_anonymousStep5"},"_anonymousStep6":{"stepId":"step//./input//withTryCatch/_anonymousStep6"},"_anonymousStep7":{"stepId":"step//./input//withThrow/_anonymousStep7"},"_anonymousStep8":{"stepId":"step//./input//withSwitch/_anonymousStep8"},"_anonymousStep9":{"stepId":"step//./input//withForOf/_anonymousStep9"}}}}*/;
 var mockModel$_anonymousStep0 = async ()=>{
     const { args } = __private_getClosureVars();
     return new MockLanguageModelV3(...args);

packages/swc-plugin-workflow/transform/tests/fixture/closure-new-expr-and-module-declarations/output-workflow.js

@@ -1,5 +1,5 @@
 // https://github.com/vercel/workflow/issues/1365
-/**__internal_workflows{"steps":{"input.js":{"_anonymousStep0":{"stepId":"step//./input//_anonymousStep0"},"_anonymousStep1":{"stepId":"step//./input//_anonymousStep1"},"_anonymousStep10":{"stepId":"step//./input//_anonymousStep10"},"_anonymousStep11":{"stepId":"step//./input//_anonymousStep11"},"_anonymousStep12":{"stepId":"step//./input//_anonymousStep12"},"_anonymousStep13":{"stepId":"step//./input//_anonymousStep13"},"_anonymousStep14":{"stepId":"step//./input//_anonymousStep14"},"_anonymousStep15":{"stepId":"step//./input//_anonymousStep15"},"_anonymousStep16":{"stepId":"step//./input//_anonymousStep16"},"_anonymousStep17":{"stepId":"step//./input//_anonymousStep17"},"_anonymousStep2":{"stepId":"step//./input//_anonymousStep2"},"_anonymousStep3":{"stepId":"step//./input//_anonymousStep3"},"_anonymousStep4":{"stepId":"step//./input//_anonymousStep4"},"_anonymousStep5":{"stepId":"step//./input//_anonymousStep5"},"_anonymousStep6":{"stepId":"step//./input//_anonymousStep6"},"_anonymousStep7":{"stepId":"step//./input//_anonymousStep7"},"_anonymousStep8":{"stepId":"step//./input//_anonymousStep8"},"_anonymousStep9":{"stepId":"step//./input//_anonymousStep9"}}}}*/;
+/**__internal_workflows{"steps":{"input.js":{"_anonymousStep0":{"stepId":"step//./input//mockModel/_anonymousStep0"},"_anonymousStep1":{"stepId":"step//./input//xai/_anonymousStep1"},"_anonymousStep10":{"stepId":"step//./input//withForIn/_anonymousStep10"},"_anonymousStep11":{"stepId":"step//./input//withDoWhile/_anonymousStep11"},"_anonymousStep12":{"stepId":"step//./input//withShorthandProps/_anonymousStep12"},"_anonymousStep13":{"stepId":"step//./input//withComputedKey/_anonymousStep13"},"_anonymousStep14":{"stepId":"step//./input//mockTextModel/_anonymousStep14"},"_anonymousStep15":{"stepId":"step//./input//withClassExpr/_anonymousStep15"},"_anonymousStep16":{"stepId":"step//./input//withClassSuper/_anonymousStep16"},"_anonymousStep17":{"stepId":"step//./input//withClassProp/_anonymousStep17"},"_anonymousStep2":{"stepId":"step//./input//mockModelWrapped/_anonymousStep2"},"_anonymousStep3":{"stepId":"step//./input//configuredStep/_anonymousStep3"},"_anonymousStep4":{"stepId":"step//./input//withOptionalChaining/_anonymousStep4"},"_anonymousStep5":{"stepId":"step//./input//withSequenceExpr/_anonymousStep5"},"_anonymousStep6":{"stepId":"step//./input//withTryCatch/_anonymousStep6"},"_anonymousStep7":{"stepId":"step//./input//withThrow/_anonymousStep7"},"_anonymousStep8":{"stepId":"step//./input//withSwitch/_anonymousStep8"},"_anonymousStep9":{"stepId":"step//./input//withForOf/_anonymousStep9"}}}}*/;
 // Bug 1: `new` expressions should have their arguments captured as closure vars
 export function mockModel(...args) {
     return globalThis[Symbol.for("WORKFLOW_USE_STEP")]("step//./input//mockModel/_anonymousStep0", ()=>({

packages/swc-plugin-workflow/transform/tests/fixture/closure-typescript-expressions/output-step.js

@@ -1,5 +1,5 @@
 import { __private_getClosureVars, registerStepFunction } from "workflow/internal/private";
-/**__internal_workflows{"steps":{"input.ts":{"_anonymousStep0":{"stepId":"step//./input//_anonymousStep0"},"_anonymousStep1":{"stepId":"step//./input//_anonymousStep1"},"_anonymousStep2":{"stepId":"step//./input//_anonymousStep2"},"_anonymousStep3":{"stepId":"step//./input//_anonymousStep3"},"_anonymousStep4":{"stepId":"step//./input//_anonymousStep4"},"_anonymousStep5":{"stepId":"step//./input//_anonymousStep5"}}}}*/;
+/**__internal_workflows{"steps":{"input.ts":{"_anonymousStep0":{"stepId":"step//./input//withTsAs/_anonymousStep0"},"_anonymousStep1":{"stepId":"step//./input//withTsSatisfies/_anonymousStep1"},"_anonymousStep2":{"stepId":"step//./input//withTsNonNull/_anonymousStep2"},"_anonymousStep3":{"stepId":"step//./input//withTsTypeAssertion/_anonymousStep3"},"_anonymousStep4":{"stepId":"step//./input//withTsConstAssertion/_anonymousStep4"},"_anonymousStep5":{"stepId":"step//./input//withGenericCall/_anonymousStep5"}}}}*/;
 var withTsAs$_anonymousStep0 = async ()=>{
     const { config } = __private_getClosureVars();
     return config as Config.timeout;

packages/swc-plugin-workflow/transform/tests/fixture/closure-typescript-expressions/output-workflow.js

@@ -1,4 +1,4 @@
-/**__internal_workflows{"steps":{"input.ts":{"_anonymousStep0":{"stepId":"step//./input//_anonymousStep0"},"_anonymousStep1":{"stepId":"step//./input//_anonymousStep1"},"_anonymousStep2":{"stepId":"step//./input//_anonymousStep2"},"_anonymousStep3":{"stepId":"step//./input//_anonymousStep3"},"_anonymousStep4":{"stepId":"step//./input//_anonymousStep4"},"_anonymousStep5":{"stepId":"step//./input//_anonymousStep5"}}}}*/;
+/**__internal_workflows{"steps":{"input.ts":{"_anonymousStep0":{"stepId":"step//./input//withTsAs/_anonymousStep0"},"_anonymousStep1":{"stepId":"step//./input//withTsSatisfies/_anonymousStep1"},"_anonymousStep2":{"stepId":"step//./input//withTsNonNull/_anonymousStep2"},"_anonymousStep3":{"stepId":"step//./input//withTsTypeAssertion/_anonymousStep3"},"_anonymousStep4":{"stepId":"step//./input//withTsConstAssertion/_anonymousStep4"},"_anonymousStep5":{"stepId":"step//./input//withGenericCall/_anonymousStep5"}}}}*/;
 // TypeScript expression wrappers should not prevent closure variable detection.
 // The plugin must traverse through `as`, `satisfies`, `!`, type assertions,
 // const assertions, and instantiation expressions to reach the inner expression.

packages/swc-plugin-workflow/transform/tests/fixture/factory-with-step-method/output-client.js

@@ -1,3 +1,4 @@
+import fs from 'fs/promises';
 /**__internal_workflows{"steps":{"input.js":{"myFactory/myStep":{"stepId":"step//./input//myFactory/myStep"}}}}*/;
 var myFactory$myStep = async function() {
     await fs.mkdir('test');

packages/swc-plugin-workflow/transform/tests/fixture/instance-method-nested-step/output-step.js

@@ -1,6 +1,6 @@
 import { registerStepFunction } from "workflow/internal/private";
 import { WORKFLOW_SERIALIZE, WORKFLOW_DESERIALIZE } from '@vercel/workflow';
-/**__internal_workflows{"steps":{"input.js":{"Service#process":{"stepId":"step//./input//Service#process"},"helper":{"stepId":"step//./input//helper"}}},"classes":{"input.js":{"Service":{"classId":"class//./input//Service"}}}}*/;
+/**__internal_workflows{"steps":{"input.js":{"Service#process":{"stepId":"step//./input//Service#process"},"helper":{"stepId":"step//./input//Service$process/helper"}}},"classes":{"input.js":{"Service":{"classId":"class//./input//Service"}}}}*/;
 var Service$process$helper = async (x)=>x * 2;
 export class Service {
     static [WORKFLOW_SERIALIZE](instance) {

packages/swc-plugin-workflow/transform/tests/fixture/nested-step-in-workflow/output-step.js

@@ -1,5 +1,5 @@
 import { registerStepFunction } from "workflow/internal/private";
-/**__internal_workflows{"workflows":{"input.js":{"example":{"workflowId":"workflow//./input//example"}}},"steps":{"input.js":{"arrowStep":{"stepId":"step//./input//arrowStep"},"helpers/objectStep":{"stepId":"step//./input//example/helpers/objectStep"},"letArrowStep":{"stepId":"step//./input//letArrowStep"},"step":{"stepId":"step//./input//step"},"varArrowStep":{"stepId":"step//./input//varArrowStep"}}}}*/;
+/**__internal_workflows{"workflows":{"input.js":{"example":{"workflowId":"workflow//./input//example"}}},"steps":{"input.js":{"arrowStep":{"stepId":"step//./input//example/arrowStep"},"helpers/objectStep":{"stepId":"step//./input//example/helpers/objectStep"},"letArrowStep":{"stepId":"step//./input//example/letArrowStep"},"step":{"stepId":"step//./input//example/step"},"varArrowStep":{"stepId":"step//./input//example/varArrowStep"}}}}*/;
 // Function declaration step
 async function example$step(a, b) {
     return a + b;

packages/swc-plugin-workflow/transform/tests/fixture/nested-step-in-workflow/output-workflow.js

@@ -1,4 +1,4 @@
-/**__internal_workflows{"workflows":{"input.js":{"example":{"workflowId":"workflow//./input//example"}}},"steps":{"input.js":{"arrowStep":{"stepId":"step//./input//arrowStep"},"helpers/objectStep":{"stepId":"step//./input//example/helpers/objectStep"},"letArrowStep":{"stepId":"step//./input//letArrowStep"},"step":{"stepId":"step//./input//step"},"varArrowStep":{"stepId":"step//./input//varArrowStep"}}}}*/;
+/**__internal_workflows{"workflows":{"input.js":{"example":{"workflowId":"workflow//./input//example"}}},"steps":{"input.js":{"arrowStep":{"stepId":"step//./input//example/arrowStep"},"helpers/objectStep":{"stepId":"step//./input//example/helpers/objectStep"},"letArrowStep":{"stepId":"step//./input//example/letArrowStep"},"step":{"stepId":"step//./input//example/step"},"varArrowStep":{"stepId":"step//./input//example/varArrowStep"}}}}*/;
 export async function example(a, b) {
     var step = globalThis[Symbol.for("WORKFLOW_USE_STEP")]("step//./input//example/step");
     // Arrow function with const

packages/swc-plugin-workflow/transform/tests/fixture/nested-step-references-module-import/input.js

@@ -0,0 +1,35 @@
+// Regression test for two related bugs:
+//
+// 1. (step mode) Imports used by a step that gets hoisted out of a
+//    workflow body must NOT be stripped by dead-code elimination. The
+//    workflow body is replaced with a `throw` proxy, so any import
+//    referenced only by the workflow body (and not by a hoisted step)
+//    should still be stripped. Truly unused imports should also be
+//    stripped.
+// 2. (cross-mode) The step ID generated for a nested anonymous step
+//    inside a *non-exported* workflow function must agree between step
+//    mode (where the step is registered) and workflow mode (where the
+//    step proxy looks it up). Both must namespace the step under the
+//    workflow function name (e.g. `step//./input//w/_anonymousStep0`).
+import { db } from './db'; // step-mode: kept (used by hoisted step)
+import { unused } from './unused'; // step-mode: stripped (truly unused)
+import * as logger from './logger'; // step-mode: kept (used by hoisted step)
+import { tool, z } from 'some-agent-lib'; // step-mode: stripped (only referenced by replaced workflow body); workflow-mode: kept
+
+async function w() {
+  'use workflow';
+  const agent = new WorkflowAgent({
+    model: 'anthropic/claude-opus-4.5',
+    tools: () => ({
+      queryDatabase: tool({
+        description: 'Query the database',
+        inputSchema: z.object({ query: z.string() }),
+        execute: async (input) => {
+          'use step';
+          logger.info('querying', input.query);
+          return db.query(input.query);
+        },
+      }),
+    }),
+  });
+}

packages/swc-plugin-workflow/transform/tests/fixture/nested-step-references-module-import/output-client.js

@@ -0,0 +1,18 @@
+// Regression test for two related bugs:
+//
+// 1. (step mode) Imports used by a step that gets hoisted out of a
+//    workflow body must NOT be stripped by dead-code elimination. The
+//    workflow body is replaced with a `throw` proxy, so any import
+//    referenced only by the workflow body (and not by a hoisted step)
+//    should still be stripped. Truly unused imports should also be
+//    stripped.
+// 2. (cross-mode) The step ID generated for a nested anonymous step
+//    inside a *non-exported* workflow function must agree between step
+//    mode (where the step is registered) and workflow mode (where the
+//    step proxy looks it up). Both must namespace the step under the
+//    workflow function name (e.g. `step//./input//w/_anonymousStep0`).
+/**__internal_workflows{"workflows":{"input.js":{"w":{"workflowId":"workflow//./input//w"}}}}*/;
+async function w() {
+    throw new Error("You attempted to execute workflow w function directly. To start a workflow, use start(w) from workflow/api");
+}
+w.workflowId = "workflow//./input//w";

packages/swc-plugin-workflow/transform/tests/fixture/nested-step-references-module-import/output-step.js

@@ -0,0 +1,28 @@
+import { registerStepFunction } from "workflow/internal/private";
+// Regression test for two related bugs:
+//
+// 1. (step mode) Imports used by a step that gets hoisted out of a
+//    workflow body must NOT be stripped by dead-code elimination. The
+//    workflow body is replaced with a `throw` proxy, so any import
+//    referenced only by the workflow body (and not by a hoisted step)
+//    should still be stripped. Truly unused imports should also be
+//    stripped.
+// 2. (cross-mode) The step ID generated for a nested anonymous step
+//    inside a *non-exported* workflow function must agree between step
+//    mode (where the step is registered) and workflow mode (where the
+//    step proxy looks it up). Both must namespace the step under the
+//    workflow function name (e.g. `step//./input//w/_anonymousStep0`).
+import { db } from './db'; // step-mode: kept (used by hoisted step)
+import { unused } from './unused'; // step-mode: stripped (truly unused)
+import * as logger from './logger'; // step-mode: kept (used by hoisted step)
+import { tool, z } from 'some-agent-lib'; // step-mode: stripped (only referenced by replaced workflow body); workflow-mode: kept
+/**__internal_workflows{"workflows":{"input.js":{"w":{"workflowId":"workflow//./input//w"}}},"steps":{"input.js":{"_anonymousStep0":{"stepId":"step//./input//w/_anonymousStep0"}}}}*/;
+var w$_anonymousStep0 = async (input)=>{
+    logger.info('querying', input.query);
+    return db.query(input.query);
+};
+async function w() {
+    throw new Error("You attempted to execute workflow w function directly. To start a workflow, use start(w) from workflow/api");
+}
+w.workflowId = "workflow//./input//w";
+registerStepFunction("step//./input//w/_anonymousStep0", w$_anonymousStep0);

packages/swc-plugin-workflow/transform/tests/fixture/nested-step-references-module-import/output-workflow.js

@@ -0,0 +1,31 @@
+// Regression test for two related bugs:
+//
+// 1. (step mode) Imports used by a step that gets hoisted out of a
+//    workflow body must NOT be stripped by dead-code elimination. The
+//    workflow body is replaced with a `throw` proxy, so any import
+//    referenced only by the workflow body (and not by a hoisted step)
+//    should still be stripped. Truly unused imports should also be
+//    stripped.
+// 2. (cross-mode) The step ID generated for a nested anonymous step
+//    inside a *non-exported* workflow function must agree between step
+//    mode (where the step is registered) and workflow mode (where the
+//    step proxy looks it up). Both must namespace the step under the
+//    workflow function name (e.g. `step//./input//w/_anonymousStep0`).
+import { tool, z } from 'some-agent-lib'; // step-mode: stripped (only referenced by replaced workflow body); workflow-mode: kept
+/**__internal_workflows{"workflows":{"input.js":{"w":{"workflowId":"workflow//./input//w"}}},"steps":{"input.js":{"_anonymousStep0":{"stepId":"step//./input//w/_anonymousStep0"}}}}*/;
+async function w() {
+    const agent = new WorkflowAgent({
+        model: 'anthropic/claude-opus-4.5',
+        tools: ()=>({
+                queryDatabase: tool({
+                    description: 'Query the database',
+                    inputSchema: z.object({
+                        query: z.string()
+                    }),
+                    execute: globalThis[Symbol.for("WORKFLOW_USE_STEP")]("step//./input//w/_anonymousStep0")
+                })
+            })
+    });
+}
+w.workflowId = "workflow//./input//w";
+globalThis.__private_workflows.set("workflow//./input//w", w);

packages/swc-plugin-workflow/transform/tests/fixture/nested-step-with-closure/output-step.js

@@ -1,7 +1,7 @@
 import { __private_getClosureVars, registerStepFunction } from "workflow/internal/private";
 import { DurableAgent } from '@workflow/ai/agent';
 import { gateway } from 'ai';
-/**__internal_workflows{"workflows":{"input.js":{"wflow":{"workflowId":"workflow//./input//wflow"}}},"steps":{"input.js":{"_anonymousStep0":{"stepId":"step//./input//_anonymousStep0"},"_anonymousStep1":{"stepId":"step//./input//_anonymousStep1"},"_anonymousStep2":{"stepId":"step//./input//_anonymousStep2"},"_anonymousStep3":{"stepId":"step//./input//_anonymousStep3"},"_anonymousStep4":{"stepId":"step//./input//_anonymousStep4"},"f":{"stepId":"step//./input//f"},"fn":{"stepId":"step//./input//fn"},"namedStepWithClosureVars":{"stepId":"step//./input//namedStepWithClosureVars"}}}}*/;
+/**__internal_workflows{"workflows":{"input.js":{"wflow":{"workflowId":"workflow//./input//wflow"}}},"steps":{"input.js":{"_anonymousStep0":{"stepId":"step//./input//stepWrapperReturnArrowFunction/_anonymousStep0"},"_anonymousStep1":{"stepId":"step//./input//arrowWrapperReturnArrowFunction/_anonymousStep1"},"_anonymousStep2":{"stepId":"step//./input//wflow/_anonymousStep2"},"_anonymousStep3":{"stepId":"step//./input//wflow/_anonymousStep3"},"_anonymousStep4":{"stepId":"step//./input//wflow/_anonymousStep4"},"f":{"stepId":"step//./input//arrowWrapperReturnNamedFunction/f"},"fn":{"stepId":"step//./input//arrowWrapperReturnNamedFunctionVar/fn"},"namedStepWithClosureVars":{"stepId":"step//./input//wflow/namedStepWithClosureVars"}}}}*/;
 var stepWrapperReturnArrowFunctionVar$fn = async ()=>{
     const { a, b, c } = __private_getClosureVars();
     return a + b + c;