Fix: Gracefully handle syntax errors in definePage to prevent Vite server crashes #692

Copilot · 2025-08-11T09:17:53Z

Problem

Syntax errors in definePage() calls would crash the Vite development server, making it impossible to continue development when there were JavaScript syntax issues in the page definition. This created a poor developer experience where a simple typo could bring down the entire dev server.

<script setup>
// This would crash the server
definePage({
  name: 'test',,  // Extra comma - syntax error
  path: '/test'
})
</script>

Solution

Enhanced error handling throughout the definePage processing pipeline to gracefully handle syntax errors and parsing failures:

Key Changes

Added comprehensive try-catch blocks in definePageTransform() and extractDefinePageNameAndPath() functions to catch any parsing or processing errors
Enhanced getCodeAst() function with error handling around Babel AST parsing to prevent syntax errors from propagating
Changed error behavior from throwing SyntaxErrors to logging warnings and returning safe fallback values:
- When extracting definePage: returns 'export default {}'
- When removing definePage from source: returns undefined (no transform)
Improved developer feedback by replacing crashes with helpful warning messages that identify the problematic file

Testing

Added comprehensive test coverage for various syntax error scenarios:

Extra commas in object literals
Missing commas between properties
Completely malformed JavaScript
Unclosed brackets
Invalid scope references

Impact

✅ Vite server no longer crashes on definePage syntax errors
✅ Development can continue with broken definePage calls (they're simply ignored)
✅ Clear warning messages help developers identify and fix issues
✅ Maintains backward compatibility for all valid definePage usage
✅ No performance impact on normal operation

The fix ensures a more robust development experience while maintaining all existing functionality for properly formatted definePage() calls.

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

cloudflare-workers-and-pages · 2025-08-11T09:20:19Z

Deploying unplugin-vue-router with Cloudflare Pages

Latest commit:	`f41937a`
Status:	✅ Deploy successful!
Preview URL:	https://0b37225b.unplugin-vue-router.pages.dev
Branch Preview URL:	https://copilot-fix-904c72ad-c6f9-42.unplugin-vue-router.pages.dev

View logs

Co-authored-by: posva <[email protected]>

src/core/definePage.spec.ts

posva · 2025-08-24T15:42:36Z

src/core/definePage.spec.ts

+
+  describe('error handling', () => {
+    it('handles syntax errors gracefully when extracting definePage', async () => {
+      const codeWithSyntaxError = `


this variable for a piece of code can be extracted in the outer scope. Share it among tests

Extracted the codeWithSyntaxError variable to the outer scope of the error handling describe block to share it among the tests, avoiding duplication. (5992675)

posva · 2025-08-24T15:43:45Z

src/core/definePage.spec.ts

+      expect(result).toBeUndefined()
+    })
+
+    it('handles malformed definePage object gracefully', async () => {


This test is redundant, syntax errors are already tested. Ensure you don't have duplicated testss

Removed the redundant "handles malformed definePage object gracefully" test as it was duplicating syntax error testing already covered by other tests. (5992675)

posva · 2025-08-24T15:44:13Z

src/core/definePage.spec.ts

+      expect(result).toBe('export default {}')
+    })
+
+    it('handles completely invalid JavaScript syntax gracefully', async () => {


same here, remove it, it's just syntax error

Removed the redundant "handles completely invalid JavaScript syntax gracefully" test as it was just another syntax error variation already covered by existing tests. (5992675)

coderabbitai · 2025-08-24T18:17:23Z

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pkg-pr-new · 2025-08-24T18:17:45Z

Open in StackBlitz

npm i https://pkg.pr.new/unplugin-vue-router@692

commit: f41937a

codecov · 2025-08-24T18:18:34Z

Codecov Report

❌ Patch coverage is 77.69784% with 31 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (feat/experimental-router@4e5015e). Learn more about missing BASE report.
⚠️ Report is 64 commits behind head on feat/experimental-router.

Files with missing lines	Patch %	Lines
src/core/definePage.ts	77.69%	31 Missing ⚠️

Additional details and impacted files

@@                     Coverage Diff                     @@
##             feat/experimental-router     #692   +/-   ##
===========================================================
  Coverage                            ?   61.10%           
===========================================================
  Files                               ?       36           
  Lines                               ?     3409           
  Branches                            ?      626           
===========================================================
  Hits                                ?     2083           
  Misses                              ?     1319           
  Partials                            ?        7

☔ View full report in Codecov by Sentry.
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🚀 New features to boost your workflow:

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posva · 2025-08-24T19:00:25Z

@copilot address the review

…, remove redundant tests Co-authored-by: posva <[email protected]>

posva

@copilot

posva · 2025-08-24T19:24:12Z

src/core/definePage.spec.ts

+    })
+
+    it('handles syntax errors gracefully when removing definePage from source', async () => {
+      const codeForRemoval = `


This piece of code is duplicated, no need to have it twice

Removed the duplicated codeForRemoval variable and now using the shared codeWithSyntaxError variable to avoid duplication. (d8052e0)

posva · 2025-08-24T19:24:32Z

src/core/definePage.spec.ts

+      expect('Failed to extract definePage info:').toHaveBeenWarned()
+    })
+
+    it('handles unclosed brackets in definePage gracefully', async () => {


this is just a syntax error, it's a redundant test

Removed the redundant "handles unclosed brackets in definePage gracefully" test as it was just another syntax error variation already covered by existing tests. (d8052e0)

…fix syntax error warning handling Co-authored-by: posva <[email protected]>

Initial plan

09c84cd

Copilot AI assigned Copilot and posva Aug 11, 2025

Copilot started work on behalf of posva August 11, 2025 09:17 View session

Fix graceful error handling for syntax errors in definePage

1923444

Co-authored-by: posva <[email protected]>

Copilot AI changed the title ~~[WIP] Can you fix this bug? Ideally a syntax error in definePage shouldn't crash the Vite server. I should gracefully handle it by ignoring the object (definePage) entirely~~ Fix: Gracefully handle syntax errors in definePage to prevent Vite server crashes Aug 11, 2025

Copilot AI requested a review from posva August 11, 2025 09:36

Copilot finished work on behalf of posva August 11, 2025 09:36

posva requested changes Aug 24, 2025

View reviewed changes

posva marked this pull request as ready for review August 24, 2025 18:17

style: fix code style

dded05e

Copilot started work on behalf of posva August 24, 2025 19:00 View session

Address review feedback: Add warning checks, extract shared variables…

5992675

…, remove redundant tests Co-authored-by: posva <[email protected]>

Copilot AI requested a review from posva August 24, 2025 19:08

Copilot finished work on behalf of posva August 24, 2025 19:08

posva requested changes Aug 24, 2025

View reviewed changes

Copilot started work on behalf of posva August 24, 2025 19:25 View session

Address review feedback: Remove duplicated code and redundant tests, …

d8052e0

…fix syntax error warning handling Co-authored-by: posva <[email protected]>

Copilot AI requested a review from posva August 24, 2025 19:33

Copilot finished work on behalf of posva August 24, 2025 19:33

posva changed the base branch from main to feat/experimental-router August 24, 2025 19:35

style: fix code style

f41937a

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Fix: Gracefully handle syntax errors in definePage to prevent Vite server crashes #692

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