Custom Error Formatter

Provide your own error handling callback instead of the built-in emoji format.

Usage

When onError is set, env-guard calls it with the array of error strings instead of throwing — you decide how to report or throw:

import { createEnv } from "@frauschert/env-guard";

const env = createEnv(schema, {
  onError: (errors) => {
    console.error("Config errors:");
    errors.forEach((e) => console.error(` - ${e}`));
    process.exit(1);
  },
});

Default Behaviour

If onError is not provided, createEnv throws an Error with the default formatted message:

🚨 Env-Guard validation errors on app start:
❌ 'PORT': Expected 'number', but got 'abc'.
❌ 'DATABASE_URL': Is marked as required but was not found.

Re-throwing

You can use onError to transform the errors and re-throw:

const env = createEnv(schema, {
  onError: (errors) => {
    throw new Error(`Config failed:\n${errors.join("\n")}`);
  },
});

With Framework Adapters

When using framework adapters, errors from both client and server schemas are collected and reported together in a single batch through onError, so you see all problems at once.