captjay98/Error Handling

Error Handling

LivestockAI uses a structured AppError class for consistent error handling across the application.

AppError Class

Located in app/lib/errors/app-error.ts:

import { AppError } from '~/lib/errors'

// Throwing errors
throw new AppError('BATCH_NOT_FOUND', {
  metadata: { batchId: '123' },
})

throw new AppError('VALIDATION_ERROR', {
  message: 'Custom message',
  metadata: { field: 'quantity' },
})

throw new AppError('ACCESS_DENIED', {
  metadata: { farmId: 'abc' },
})

Error Codes

Common error codes defined in app/lib/errors/error-map.ts:

| Code | HTTP Status | Category | Usage | | ---------------- | ----------- | ---------- | ------------------- | | VALIDATION_ERROR | 400 | validation | Invalid input | | ACCESS_DENIED | 403 | auth | No permission | | BATCH_NOT_FOUND | 404 | not_found | Resource missing | | DATABASE_ERROR | 500 | database | DB operation failed |

AppError Structure

class AppError extends Error {
  reason: ReasonCode // e.g., 'BATCH_NOT_FOUND'
  code: number // Internal code
  httpStatus: number // HTTP status code
  category: string // Error category
  metadata: ErrorMetadata // Additional context
}

Using in Server Functions

export const getBatchFn = createServerFn({ method: 'GET' })
  .inputValidator(z.object({ batchId: z.string().uuid() }))
  .handler(async ({ data }) => {
    const { requireAuth } = await import('../auth/server-middleware')
    const session = await requireAuth()

    const { getDb } = await import('~/lib/db')
    const db = await getDb()

    const batch = await getBatchById(db, data.batchId)
    if (!batch) {
      throw new AppError('BATCH_NOT_FOUND', {
        metadata: { batchId: data.batchId },
      })
    }

    const hasAccess = await checkFarmAccess(session.user.id, batch.farmId)
    if (!hasAccess) {
      throw new AppError('ACCESS_DENIED', {
        metadata: { farmId: batch.farmId },
      })
    }

    return batch
  })

Error Handling Pattern

try {
  // Operation
} catch (error) {
  if (error instanceof AppError) {
    // Re-throw known errors
    throw error
  }
  // Wrap unknown errors
  throw new AppError('DATABASE_ERROR', {
    message: 'Failed to complete operation',
    cause: error,
  })
}

Type Checking

if (AppError.isAppError(error)) {
  console.log(error.reason) // 'BATCH_NOT_FOUND'
  console.log(error.httpStatus) // 404
  console.log(error.metadata) // { batchId: '123' }
}

JSON Serialization

const json = error.toJSON()
// {
//   name: 'AppError',
//   reason: 'BATCH_NOT_FOUND',
//   code: 1001,
//   httpStatus: 404,
//   category: 'not_found',
//   message: 'Batch not found',
//   metadata: { batchId: '123' }
// }

const restored = AppError.fromJSON(json)

Client-Side Error Handling

import { useMutation } from '@tanstack/react-query'
import { toast } from 'sonner'

const mutation = useMutation({
  mutationFn: createBatchFn,
  onError: (error) => {
    if (error.message.includes('ACCESS_DENIED')) {
      toast.error('You do not have access to this farm')
    } else if (error.message.includes('VALIDATION_ERROR')) {
      toast.error('Please check your input')
    } else {
      toast.error('An error occurred. Please try again.')
    }
  },
})

Related Skills

• three-layer-architecture - Error handling in layers
• tanstack-start - Server function error handling