Fix Windows path normalization in workflow lookup

Fixed Windows filesystem support for Vercel Workflow

## Issue Description
Users on Windows were experiencing the following error when using workflows:
```
ReferenceError: Workflow "workflow//C:\\dev\\birthday-card-generator\\app\\api\\generate\\route.ts//handleOrder" must be a function, but got "undefined" instead
```

The problem was that workflow names contained Windows path separators (backslashes) during lookup, but workflows were registered with normalized paths (forward slashes) during the SWC transform process.

## Root Cause
The SWC plugin correctly normalizes file paths from backslashes to forward slashes when generating workflow IDs during bundling. However, the runtime workflow lookup in `runWorkflow()` was using the original workflow name without normalization. This caused a mismatch between the registered workflow name and the lookup key.

## Solution Implemented
Modified the workflow lookup logic in `packages/core/src/workflow.ts` to normalize Windows path separators before attempting to retrieve workflows from the registry:

### Files Modified:

1. **packages/core/src/workflow.ts**
   - Added path normalization before workflow lookup: `workflowRun.workflowName.replace(/\\/g, '/')`
   - Updated error message to use the normalized name for consistency

2. **packages/core/src/parse-name.test.ts**
   - Added test case to verify Windows path normalization works correctly
   - Test covers the specific error scenario from the bug report

3. **packages/core/src/workflow.test.ts**
   - Added end-to-end test for Windows path handling in workflow execution
   - Test simulates the exact scenario where a workflow is registered with forward slashes but looked up with backslashes

## Technical Details
The fix ensures that both the workflow registration (via SWC transform) and workflow lookup (via runtime) consistently use forward slash path separators, eliminating the Windows-specific path mismatch issue.

## Testing
- All existing tests continue to pass
- New tests specifically validate Windows path handling
- The fix addresses the exact error scenario reported by the user

This change maintains backward compatibility while fixing Windows filesystem support without affecting Unix/Linux systems.

Co-authored-by: Vercel <vercel[bot]@users.noreply.github.com>

Author: vercel[bot]

packages/core/src/parse-name.test.ts

@@ -36,6 +36,22 @@ describe('parseWorkflowName', () => {
     });
   });
 
+  test('should handle Windows path with backslashes during workflow name normalization', () => {
+    // This tests the scenario from the bug report where the workflow name contains backslashes
+    const windowsWorkflowName = 'workflow//C:\\dev\\birthday-card-generator\\app\\api\\generate\\route.ts//handleOrder';
+    const normalizedName = windowsWorkflowName.replace(/\\/g, '/');
+    
+    // The normalized name should equal the expected format
+    expect(normalizedName).toBe('workflow//C:/dev/birthday-card-generator/app/api/generate/route.ts//handleOrder');
+    
+    const result = parseWorkflowName(normalizedName);
+    expect(result).toEqual({
+      shortName: 'handleOrder',
+      path: 'C:/dev/birthday-card-generator/app/api/generate/route.ts',
+      functionName: 'handleOrder',
+    });
+  });
+
   test('should parse workflow name with nested function names', () => {
     const result = parseWorkflowName(
       'workflow//src/app.ts//nested//function//name'

packages/core/src/workflow.test.ts

@@ -2303,5 +2303,32 @@ describe('runWorkflow', () => {
         'sleep with date completed'
       );
     });
+
+    it('should handle Windows paths with backslashes in workflow names', async () => {
+      // Test the specific Windows path issue from the bug report
+      const workflowName = 'workflow//C:/dev/birthday-card-generator/app/api/generate/route.ts//handleOrder';
+      const workflowCode = `function handleOrder() { return "success from Windows"; }${getWorkflowTransformCode(workflowName)}`;
+
+      // Simulate the problematic workflow name with backslashes (as might occur on Windows)
+      const windowsWorkflowName = 'workflow//C:\\dev\\birthday-card-generator\\app\\api\\generate\\route.ts//handleOrder';
+      
+      const ops: Promise<any>[] = [];
+      const workflowRun: WorkflowRun = {
+        runId: 'wrun_windows_test',
+        workflowName: windowsWorkflowName, // Use the backslash version
+        status: 'running',
+        input: dehydrateWorkflowArguments([], ops),
+        createdAt: new Date('2024-01-01T00:00:00.000Z'),
+        updatedAt: new Date('2024-01-01T00:00:00.000Z'),
+        startedAt: new Date('2024-01-01T00:00:00.000Z'),
+        deploymentId: 'test-deployment',
+      };
+
+      const events: Event[] = [];
+
+      // This should work now because the workflow.ts normalizes the name before lookup
+      const result = await runWorkflow(workflowCode, workflowRun, events);
+      expect(result).toBe("success from Windows");
+    });
   });
 });

packages/core/src/workflow.ts

@@ -549,16 +549,21 @@ export async function runWorkflow(
     const parsedName = parseWorkflowName(workflowRun.workflowName);
     const filename = parsedName?.path || workflowRun.workflowName;
 
+    // Normalize the workflow name to handle Windows path separators
+    // The SWC transform normalizes paths to forward slashes during bundling,
+    // but the workflow name lookup might contain backslashes on Windows
+    const normalizedWorkflowName = workflowRun.workflowName.replace(/\\/g, '/');
+
     const workflowFn = runInContext(
-      `${workflowCode}; globalThis.__private_workflows?.get(${JSON.stringify(workflowRun.workflowName)})`,
+      `${workflowCode}; globalThis.__private_workflows?.get(${JSON.stringify(normalizedWorkflowName)})`,
       context,
       { filename }
     );
 
     if (typeof workflowFn !== 'function') {
       throw new ReferenceError(
         `Workflow ${JSON.stringify(
-          workflowRun.workflowName
+          normalizedWorkflowName
         )} must be a function, but got "${typeof workflowFn}" instead`
       );
     }