I’m trying to figure out how to get yada to select a content-type for a response based on a query param. The resource is set to produce #{"text/html" "application/json;q=0.9"}, as html should be the default if there’s no Accept header and no relevant query param. However, the API user can send the param json=true which should act as if they has sent an Accept header of application/json. I know this is not good API design, but I have to support it for legacy reasons. In any case, I either produce an HTML string or a Clojure map based on (or json (.contains (yada/content-type ctx) "json")). I thought that yada would take a Clojure map and the fact that application/json is an allowed production type and produce an application/json response, but it produces HTML. If I remove the quality ranking, I always get JSON, even for the strings. How can I set the content-type based purely on the data type I have to return when I don’t have an Accept header?

Should I manipulate the context by setting the request Accept header based on the query param?

The manual says that if I want complete control of the response, I can return a modified Response taken from the ctx, but that already has the negotiated media type set on it, which is text/html when there’s no accept header.

Yes, you can return the response and you can override that content type

You've figured it out

Thanks

But the response looks like this right before I get I change to modify it: #yada.context.Response{:headers {}, :vary #{:media-type}, :produces {:media-type #yada.media_type.MediaTypeMap{:name text/html, :type text, :subtype html, :parameters {}, :quality 1.0}, :charset #yada.charset.CharsetMap{:alias UTF-8, :quality 1.0}}

After: #yada.context.Response{:headers {content-type application/json}, :vary #{:media-type}, :produces {:media-type #yada.media_type.MediaTypeMap{:name text/html, :type text, :subtype html, :parameters {}, :quality 1.0}, :charset #yada.charset.CharsetMap{:alias UTF-8, :quality 1.0}}, :body ...}

And I still get html, so I must be doing something wrong

What did you modify?

I set the header and body

If you are returning the response yourself you then have to do the conversion of the body to whatever you need.

But the produces seems to win

Yada won't automatically convert for you

Content negotiation happens before the response function

You can renegotiate manually but its off piste

Off piste?

I think ideally I'd prefer to renegotiate manually as that seems cleaner. Just don't know how

Sorry, an expression meaning you're straying outside of yada 's functionality but this tends to happen when you are forced to cope with bad practices

Exactly my case lol

There's code in the yada conneg ns

Okay I'll take a look

This works:

(if json
        (-> response
            (assoc-in [:produces :media-type] (yada.media-type/string->media-type "application/json"))
            (assoc :body body))
        body)

@malcolmsparks thanks for your help