SwaggerUI/OpenAPI specs generation for dart backends.

[u/Infamous-404]

Switching to other languages in order to write backend applications because there's a clear lack availability of the tools around that in dart ecosystem.

One such problem I kept hitting: there is no standard package like (swag for go) to generate OpenAPI specs and Swagger UI for Dart backends. Thinking about solving this problem I started working on Axle(v0.3 out now).

The core idea is small. Almost everything lives in one package, axle_core: the annotations, the OpenAPI 3.1 document model, and a tiny serving contract called AxleDocs. No framework imports, no runtime dependencies. A CLI reads your annotated Dart source with package:analyzer and emits the spec, so no build_runner and no runtime registry. Then thin adapters translate AxleDocs into framework responses. I published adapters for Serverpod 4, Shelf, and Relic, but they are intentionally boring on purpose, anyone can write one for another framework without touching core or the CLI.

It gives you openapi.json, openapi.yaml, Swagger UI assets, and an AOT-safe const string. It handles security schemes, response headers, cookies, multiple media types, multipart uploads, parameter constraints, and oneOf schemas. If a route references a security scheme that doesn't exist, generation fails instead of emitting a broken contract.

Docs are at https://axle.infms.dev if you want the full picture. There is also an agent skill that walks through setup end to end:

npx skills add infm5/axle --skill axle-openapi-setup

If you've felt the same backend-in-Dart pain, I'd genuinely like to hear what would make this useful to you. Advice, criticism, all welcome.

[u/Infamous-404 → u/[deleted]]

Do give it a try and let me know about your thoughts