configuration resolution patterns

When defining configuration schemas, use consistent patterns for safe property access, async resolution, and default value handling. Always use optional chaining with fallback values for nested configuration properties, leverage $resolve for complex async configuration logic, and ensure proper backwards compatibility.

Key patterns to follow:

1. Safe property access: Use optional chaining with fallbacks for nested config properties:

   const extraKeys = nuxt.options?.experimental?.extraPageMetaExtractionKeys || []
   

2. Async configuration resolution: Use $resolve for complex configuration logic that requires async operations or cross-property dependencies:

   serverDir: {
     $resolve: async (val: string | undefined, get): Promise<string> => {
    return resolve(await get('rootDir') as string, val ?? 'server')
     }
   }
   

3. Default value merging: Use defu for merging configuration objects with proper defaults:

   spaLoaderAttrs: {
     $resolve: (val: undefined | null | Record<string, unknown>) => {
    return defu(val, {
      id: val?.id ?? '__nuxt-spa-loader',
    })
     }
   }
   

4. Backwards compatibility: Check for legacy configuration options when introducing new patterns:

   propsDestructure: {
     $resolve: async (val, get) => {
    // Check both new and legacy locations
    return val ?? Boolean((await get('vue') as Record<string, any>).propsDestructure)
     }
   }
   

5. Runtime config handling: Distinguish between undefined (not set) and null (explicitly set to null) values:

   // Only filter out undefined, preserve null values for runtime override capability
   if (typeof obj[key] === 'undefined') {
     // handle undefined case
   }
   

This ensures configuration is resolved consistently, safely handles missing values, and maintains backwards compatibility while supporting complex async resolution scenarios.