Fix: Cannot Combine Flow and TypeScript Plugins in Vue.js - Vue.js Error Fix

What Causes This Error?

This error occurs when you try to enable both Flow and TypeScript parsers simultaneously in Vue’s compiler configuration. They are mutually exclusive type systems.

The Problem

// ❌ Both type systems enabled
{
  parserPlugins: ['typescript', 'flow']
}

The Fix

Choose One Type System

// ✅ TypeScript only (recommended)
{
  parserPlugins: ['typescript']
}

// ✅ Or Flow only
{
  parserPlugins: ['flow']
}

Vite Configuration

// vite.config.js
import vue from '@vitejs/plugin-vue'

export default {
  plugins: [
    vue({
      script: {
        // ✅ Use TypeScript
        babelParserPlugins: ['typescript']
      }
    })
  ]
}

Migrating from Flow to TypeScript

If you have Flow code and want to migrate:

# Install TypeScript
npm install -D typescript

# Convert Flow files
npx flow-to-ts src/**/*.js

Check Your Configuration

// Remove conflicting configuration
export default {
  plugins: [
    vue({
      script: {
        // Only one of these, not both
        babelParserPlugins: ['typescript'] // or ['flow']
      }
    })
  ]
}

Quick Checklist

Choose either TypeScript OR Flow, not both
Check Vite/webpack configuration for duplicate plugins
Migrate Flow to TypeScript if needed
TypeScript is the recommended choice for Vue 3