Common server configuration

Status codes

By default, successful responses are returned with the 200 OK status code, and errors with 400 Bad Request. However, this can be customised when interpreting an endpoint as a directive/route, by providing implicit values of type StatusMapper[T] = T => StatusCode, where type StatusCode = Int.

This can be especially useful for error responses, in which case having an Endpoint[I, E, O, S], you’d need to provide an implicit StatusMapper[E].

Server options

Each interpreter accepts an implicit options value, which contains configuration values for:

  • how to create a file (when receiving a response that is mapped to a file, or when reading a file-mapped multipart part)
  • how to handle decode failures

Handling decode failures

Quite often user input will be malformed and decoding will fail. Should the request be completed with a 400 Bad Request response, or should the request be forwarded to another endpoint? By default, tapir follows OpenAPI conventions, that an endpoint is uniquely identified by the method and served path. That’s why:

  • an “endpoint doesn’t match” result is returned if the request method or path doesn’t match. The http library should attempt to serve this request with the next endpoint.
  • otherwise, we assume that this is the correct endpoint to serve the request, but the parameters are somehow malformed. A 400 Bad Request response is returned if a query parameter, header or body is missing / decoding fails, or if the decoding a path capture fails with an error (but not a “missing” decode result).

This can be customised by providing an implicit instance of tapir.server.DecodeFailureHandler, which basing on the request, failing input and failure description can decide, whether to return a “no match”, an endpoint-specific error value, or a specific response.

Only the first failure is passed to the DecodeFailureHandler. Inputs are decoded in the following order: method, path, query, header, body.