js/src/util/context.ts


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import { AsyncLocalStorage } from "async_hooks";

export namespace Context {
  export class NotFound extends Error {
    constructor(public readonly name: string) {
      super(`No context found for ${name}`);
    }
  }

  export function create<T>(name: string) {
    const storage = new AsyncLocalStorage<T>();
    return {
      use() {
        const result = storage.getStore();
        if (!result) {
          throw new NotFound(name);
        }
        return result;
      },
      provide<R>(value: T, fn: () => R) {
        return storage.run<R>(value, fn);
      },
    };
  }
}