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PKU685: Middleware Handler Invalid

Error Message​

[PKU685] Handler for pikkuMiddleware is not a function.

What Went Wrong​

You're trying to register middleware, but the provided handler is not a valid function. Middleware must be wrapped with pikkuMiddleware().

How to Fix​

Use pikkuMiddleware to define your middleware:

import { pikkuMiddleware } from '#pikku'

// ✅ Correct: Valid middleware
export const logRequest = pikkuMiddleware(async (ctx, next) => {
  console.log(`Request: ${ctx.method} ${ctx.path}`)
  return await next()
})

Then use it in your routes:

import { wireHTTP } from '@pikku/core/http'
import { myHandler } from './handlers'
import { logRequest } from './middleware'

wireHTTP({
  method: 'post',
  route: '/api/users',
  func: myHandler,
  middleware: [logRequest], // Apply middleware
})

Middleware Factory Pattern​

For parameterized middleware, use pikkuMiddlewareFactory:

import { pikkuMiddlewareFactory } from '#pikku'

// Factory that creates middleware
export const rateLimiter = pikkuMiddlewareFactory((limit: number) => {
  return pikkuMiddleware(async (ctx, next) => {
    // Check rate limit
    if (requestCount > limit) {
      throw new Error('Rate limit exceeded')
    }
    return await next()
  })
})

// Usage
wireHTTP({
  method: 'post',
  route: '/api/data',
  func: myHandler,
  middleware: [rateLimiter(100)], // Create middleware with parameter
})

Common Patterns​

Logging Middleware​

export const logger = pikkuMiddleware(async (ctx, next) => {
  const start = Date.now()
  const result = await next()
  const duration = Date.now() - start
  console.log(`${ctx.method} ${ctx.path} - ${duration}ms`)
  return result
})

Authentication Middleware​

export const requireAuth = pikkuMiddleware(async (ctx, next) => {
  if (!ctx.session?.userId) {
    throw new Error('Unauthorized')
  }
  return await next()
})

Error Handling Middleware​

export const errorHandler = pikkuMiddleware(async (ctx, next) => {
  try {
    return await next()
  } catch (error) {
    console.error('Request failed:', error)
    throw error
  }
})

Common Mistakes​

  • Using a regular function instead of pikkuMiddleware
  • Forgetting to call next()
  • Not returning the result from next()
  • Providing null or undefined as middleware
  • PKU835 - Permission Handler Invalid