Fix default export workflow function transformation in workflow mode (#373)

Fixed a bug where default export workflow functions with names (e.g., `export default async function testWorkflow()`) would fail at runtime with `ReferenceError: $$default is not defined`. The SWC plugin now correctly keeps the default export as-is and simply adds the workflowId assignment after it, since the function name is available as a binding in the module scope.

Also adds support for anonymous and arrow function default exports, which previously were not being transformed at all.

Fixes #367.

Author: TooTallNate

.changeset/fix-default-export-workflow.md

@@ -0,0 +1,5 @@
+---
+"@workflow/swc-plugin": patch
+---
+
+Fix default export workflow function transformation in workflow mode

packages/swc-plugin-workflow/transform/src/lib.rs

@@ -0,0 +1,7 @@
+// Test anonymous default export workflow
+export default async function() {
+  'use workflow';
+  const result = await someStep();
+  return result;
+}
+

packages/swc-plugin-workflow/transform/tests/fixture/anonymous-default-workflow/input.js

@@ -0,0 +1,7 @@
+// Test anonymous default export workflow
+/**__internal_workflows{"workflows":{"input.js":{"default":{"workflowId":"workflow//input.js//__default"}}}}*/;
+const __default = async function() {
+    throw new Error("You attempted to execute workflow __default function directly. To start a workflow, use start(__default) from workflow/api");
+};
+__default.workflowId = "workflow//input.js//__default";
+export default __default;

packages/swc-plugin-workflow/transform/tests/fixture/anonymous-default-workflow/output-client.js

@@ -0,0 +1,7 @@
+// Test anonymous default export workflow
+/**__internal_workflows{"workflows":{"input.js":{"default":{"workflowId":"workflow//input.js//__default"}}}}*/;
+export default async function() {
+    'use workflow';
+    const result = await someStep();
+    return result;
+}

packages/swc-plugin-workflow/transform/tests/fixture/anonymous-default-workflow/output-step.js

@@ -0,0 +1,8 @@
+// Test anonymous default export workflow
+/**__internal_workflows{"workflows":{"input.js":{"default":{"workflowId":"workflow//input.js//__default"}}}}*/;
+const __default = async function() {
+    const result = await someStep();
+    return result;
+};
+__default.workflowId = "workflow//input.js//__default";
+export default __default;

packages/swc-plugin-workflow/transform/tests/fixture/anonymous-default-workflow/output-workflow.js

@@ -0,0 +1,7 @@
+// Test default export arrow workflow
+export default async (data) => {
+  'use workflow';
+  const processed = await processData(data);
+  return processed;
+};
+

packages/swc-plugin-workflow/transform/tests/fixture/default-arrow-workflow/input.js

@@ -0,0 +1,7 @@
+// Test default export arrow workflow
+/**__internal_workflows{"workflows":{"input.js":{"default":{"workflowId":"workflow//input.js//__default"}}}}*/;
+const __default = async (data)=>{
+    throw new Error("You attempted to execute workflow __default function directly. To start a workflow, use start(__default) from workflow/api");
+};
+__default.workflowId = "workflow//input.js//__default";
+export default __default;

packages/swc-plugin-workflow/transform/tests/fixture/default-arrow-workflow/output-client.js

@@ -0,0 +1,7 @@
+// Test default export arrow workflow
+/**__internal_workflows{"workflows":{"input.js":{"default":{"workflowId":"workflow//input.js//__default"}}}}*/;
+export default (async (data)=>{
+    'use workflow';
+    const processed = await processData(data);
+    return processed;
+});

packages/swc-plugin-workflow/transform/tests/fixture/default-arrow-workflow/output-step.js

@@ -0,0 +1,8 @@
+// Test default export arrow workflow
+/**__internal_workflows{"workflows":{"input.js":{"default":{"workflowId":"workflow//input.js//__default"}}}}*/;
+const __default = async (data)=>{
+    const processed = await processData(data);
+    return processed;
+};
+__default.workflowId = "workflow//input.js//__default";
+export default __default;