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The defineConfig function is a type inference helper that provides TypeScript intellisense and validation for your Saykit configuration file.

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Signature

function defineConfig<C extends input<typeof Configuration>>(
  config: C
): C
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config
Configuration
required
Your Saykit configuration object
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return
C
The same configuration object, with full type inference

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Purpose

This function is a pass-through identity function that exists solely to provide TypeScript type inference. It:
  • Returns the exact same object you pass in
  • Provides autocomplete for configuration options
  • Validates your configuration against the Saykit schema
  • Helps catch configuration errors at development time
defineConfig uses Zod’s input type to validate the configuration schema. This ensures your config matches the expected structure.

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Usage

Use defineConfig in your saykit.config.ts file to get full TypeScript support:
saykit.config.ts
import { defineConfig } from 'saykit/config';

export default defineConfig({
  include: ['src/**/*.{ts,tsx}'],
  exclude: ['**/*.test.ts', '**/*.spec.ts'],
  output: {
    path: './locales',
    format: 'json',
  },
  locales: ['en', 'es', 'fr'],
  sourceLocale: 'en',
});

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Benefits

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1. Autocomplete

Your editor will suggest valid configuration options as you type: 
export default defineConfig({
  // Type "out" and see suggestions: output, ...
  output: {
    // Type "f" and see suggestions: format, ...
  },
});

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2. Type Safety

Invalid configurations are caught immediately: 
export default defineConfig({
  output: {
    format: 'xml', // ❌ Error: 'xml' is not a valid format
  },
});

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3. Documentation

Hover over any property to see inline documentation: 
export default defineConfig({
  sourceLocale: 'en', // 👆 Hover to see: "The source locale for your project"
});

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Without defineConfig

You can still export a plain object, but you’ll lose type checking and autocomplete: 
// This works, but no type safety
export default {
  include: ['src/**/*.ts'],
  output: { path: './locales' },
};

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