Failed outputs are rendered as responses with no body

I’m trying to upgrade to 0.14 (from 0.11), and I’m encountering an issue with custom error responses. I am using finch-circe, and I have a custom Encoder[Exception] which is imported into the implicit scope where I’m calling toServiceAs, but I don’t see my custom output. Also, logging that I injected into my encoder never fires, which further indicates that my code is not getting run.

I see responses that look like:

HTTP/1.1 400 Bad Request
Content-Length: 0
Date: Fri, 21 Apr 2017 18:05:39 GMT
Vary: Origin

@vkostyukov notes that the date header means Finch is processing the response, because finagle by itself doesn’t have that. However, even if there was no message, the default Encoder[Exception] instance would seem to return "{message:null}" in the body, in the event of a missing message. It’s not clear why the bodies are missing entirely.

[rpless]

Hi @anatoliykmetyuk, it looks the rendering of the docs is a little messed up, but if you look at the bottom of this section, it shows that you can do this:

implicit val encodeExceptionCirce: Encoder[Exception] = 
  Encoder.instance(e =>	
    Json.obj(“message” -> Option(e.getMessage).fold(Json.Null)(Json.fromString)))

I’ll try to fix those up later so its clearer how to render errors.

[ComFreek]

Note that https://finagle.github.io/finch/user-guide.html#errors (that @rpless referenced above) contains a much more elaborated code snippet now than the comment above.