@leancodepl/validation

TypeScript library for handling validation errors in CQRS command responses with type-safe error code mapping.

Installation

npm install @leancodepl/validation
# or
yarn add @leancodepl/validation

API

handleValidationErrors(validationErrors, errorCodesMap, validationResults)

Creates a validation error handler that processes errors with type-safe error code mapping.

Parameters:

• validationErrors: ValidationError<TAllErrors>[] - Array of validation errors to process
• errorCodesMap: TAllErrors - Mapping of error names to numeric codes
• validationResults?: TInResult[] - Optional array of previous handler results

Returns: Handler with handle, handleAll, and check methods

handleResponse(response, errorCodesMap)

Handles CQRS command responses and transforms them into validation error handlers.

Parameters:

• response: ApiResponse<CommandResult<TErrors>> - API response containing command result
• errorCodesMap: TErrors - Mapping of error names to numeric codes

Returns: Validation error handler with success/failure support

Usage Examples

Basic Error Handling

import { handleValidationErrors } from "@leancodepl/validation"

const errorCodes = { EmailExists: 1, InvalidEmail: 2 } as const
const errors = [{ ErrorCode: 1, ErrorMessage: "Email exists", PropertyName: "Email" }]

handleValidationErrors(errors, errorCodes)
  .handle("EmailExists", () => console.log("Email already registered"))
  .handle("InvalidEmail", () => console.log("Invalid email format"))
  .check()

Command Response Handling

import { handleResponse } from "@leancodepl/validation"

const errorCodes = { UserNotFound: 1 } as const
const response = await fetch("/api/users/123", { method: "PUT", body: JSON.stringify({ name: "John" }) })

handleResponse(response, errorCodes)
  .handle("success", () => console.log("User updated"))
  .handle("UserNotFound", () => console.log("User not found"))
  .handle("failure", () => console.log("Request failed"))
  .check()

Multiple Error Handling

import { handleValidationErrors } from "@leancodepl/validation"

const errorCodes = { Required: 1, Invalid: 2 } as const
const errors = [
  { ErrorCode: 1, PropertyName: "email", ErrorMessage: "Email required" },
  { ErrorCode: 2, PropertyName: "name", ErrorMessage: "Invalid name" },
]

handleValidationErrors(errors, errorCodes)
  .handleAll(["Required", "Invalid"], errorGroups => {
    errorGroups.forEach(({ errors }) => {
      errors.forEach(error => console.log(`${error.PropertyName}: ${error.ErrorMessage}`))
    })
  })
  .check()

Success/Failure Result Processing

import { handleResponse } from "@leancodepl/validation"

const errorCodes = { InvalidData: 1 } as const
const response = await fetch("/api/data")

const isSuccess = handleResponse(response, errorCodes)
  .handle("success", () => true)
  .handle(["InvalidData", "failure"], () => false)
  .check({
    reducer: (prev, current) => prev && current,
    initialValue: true,
  })