openapi-metadata/src/metadata/factory.ts

Auto-Generate OpenAPI specifications from Typescript decorators

import deepmerge from "deepmerge";

export function createMetadataStorage<T extends Object>(key: Symbol | string, defaultMetadata?: T) {
  function defineMetadata(object: Object, metadata: T, propertyKey?: string | symbol) {
    if (propertyKey) {
      Reflect.defineMetadata(key, metadata, object, propertyKey);
    } else {
      Reflect.defineMetadata(key, metadata, object);
    }
  }

  function getMetadata(object: Object, propertyKey?: string | symbol, withParent = false): T {
    if (propertyKey) {
      let metadata = Reflect.getMetadata(key, object, propertyKey) ?? defaultMetadata;

      if (withParent) {
        metadata = deepmerge(getMetadata(object.constructor), metadata);
      }

      return metadata;
    } else {
      return Reflect.getMetadata(key, object) ?? defaultMetadata;
    }
  }

  function mergeMetadata(object: Object, metadata: T, propertyKey?: string | symbol): T {
    const existing = getMetadata(object, propertyKey);
    const merged = deepmerge(existing, metadata) as T;
    defineMetadata(object, merged, propertyKey);
    return merged;
  }

  return {
    defineMetadata,
    getMetadata,
    mergeMetadata,
  };
}