Unifying TypeScript and Dart for a Serverless FaaS Platform at Xianyu

Xianyu's Serverless infrastructure shifted toward the Dart ecosystem, unifying the language for front-end and back-end to improve FaaS development efficiency.

The main obstacles were language disunity and fragmented engineering: front-end developers faced a steep learning curve due to unfamiliar Dart and its ecosystem, while separate front-end and FaaS projects duplicated build, debug, and release toolchains.

To solve this, a TypeScript-to-Dart source-to-source translator was built. The translator works in four layers: (1) basic syntax conversion, (2) native method differences (e.g., list2.push(10) in TS becomes list2.add(10) in Dart, resolved via the TS TypeChecker to map methods to their originating classes), (3) business framework bridging (generating declaration files for services like HsfServices.request and data models such as DartMtopResult), and (4) dependency and header bridging (mapping NPM packages to Dart pub dependencies via a faas.yaml file).

An example of the generated declaration is shown below:

export declare class HsfServices { static request(moduletName: string, parameter: string): Promise<DartMtopResult<string>>; }

For dependency mapping, a faas.yaml specifies the Dart package and entry point:

faas_pub:
  hsf_services: ^1.1.7
  index: hsf_services.dart

Engineering integration followed: the front-end scaffold now fully manages the FaaS project, exposing only init and dev commands, while a real-time compiler syncs translated Dart code into the black-boxed FaaS runtime.

The result is a unified technology stack that gives developers a familiar TypeScript experience, eliminates engineering silos, and provides a smooth path toward further initiatives such as data-structure unification and automated packaging.

Future work includes refining debugging, publishing, rollback mechanisms, and extending the approach to other language pairs.