Debugging CRA to Vite Migrations - A Systematic Approach

gen-ai-writen source cusor ide agent mode auto likely claude 3.7

related: CRA to Vite Migration - Specific Patterns and Fixes

1. Error Prioritization

The Console Hierarchy

When debugging migration issues, always start with the topmost error in the console. This is often the root cause, with subsequent errors being cascading effects.

Example:

// Top error (root cause)
Uncaught TypeError: Cannot read properties of undefined (reading 'notify')
    at ErrorBoundary.componentDidCatch
 
// Subsequent errors (effects)
React will try to recreate this component tree...
Error in <Component>...

Why This Matters

• Later errors are often symptoms, not causes
• Fixing the root error often resolves cascading issues
• Error boundaries can mask the original problem

2. Using Git for Comparison

The Two-Branch Strategy

1. Control Branch: Original CRA version
2. Errors Branch: Vite migration with issues

Effective Git Commands

# Compare specific file between branches
git diff control-branch errors-branch -- path/to/file.jsx
 
# See what changed in a file
git log -p path/to/file.jsx
 
# Check when a file was last modified
git blame path/to/file.jsx

When to Use This

• When behavior changes but file appears unchanged
• To verify if changes were made to a file
• To track down when a pattern was introduced
• To compare working vs non-working versions

3. Practical Debugging Steps

1. Start with Console

   • Identify topmost error
   • Note the component and line number
   • Look for initialization issues

2. Check Git History

   • Compare working vs non-working versions
   • Look for subtle changes
   • Verify file modifications

3. Isolate the Issue

   • Create minimal reproduction
   • Test in isolation
   • Verify fixes before moving on

4. Common Migration Patterns to Check

File Comparison Checklist

• SVG imports and usage
• Function declaration order
• Error boundary initialization
• Environment variable access
• Global variable usage
• Module imports/exports

5. Tools and Techniques

Console Debugging

// Add strategic console logs
console.log('Component mounted:', {
  props,
  state,
  context
});
 
// Check initialization
console.log('Error boundary initialized:', {
  errorService: typeof ErrorService?.notify
});

Git Investigation

# See all changes to a file
git log --follow -p path/to/file.jsx
 
# Find when a pattern was introduced
git grep "pattern" $(git rev-list --all)

Key Takeaways

1. Error Order Matters

   • Start with the first error
   • Don’t be distracted by cascading errors
   • Error boundaries can hide root causes

2. Use Version Control

   • Compare working vs non-working
   • Track down when changes occurred
   • Verify file modifications

3. Systematic Approach

   • Isolate the issue
   • Create minimal reproduction
   • Test fixes in isolation

4. Document Patterns

   • Note what worked in CRA
   • Document Vite requirements
   • Create migration guides

Example Workflow

1. See error in console
2. Note topmost error message
3. Check git history of affected file
4. Compare with working version
5. Identify migration-specific issue
6. Apply fix
7. Verify resolution
8. Document pattern