Response validation doesn't support media types with wildcards

[adrienyhuel]

I found out that response validation can't handle wildcard content types.

The OpenAPI spec can define response conte type with wildcards, like "application/", "/*"....

Sample extracted from open website https://swagger.io/docs/specification/v3_0/media-types/ :

paths:
  /info/logo:
    get:
      responses:
        "200": # Response
          description: OK
          content: # Response body
            image/*: # Media type
              schema:
                type: string
                format: binary

In my case, the OpenAPI Spec had a ContentType "/"
If the backend send a response with the Content-Type header "application/json", the validation fail with an error :

POST / 200 operation response content type 'application/json' does not exist","reason":"The content type 'application/json' of the POST response received has not been defined, it's an unknown type

If the backend respond with Content-Type "/", there is no error, but the body is not validated as there is no parser for that content type.

I think there is two places where the response Content-Type is compared to the OpenAPI Spec :

libopenapi-validator/responses/validate_body.go

Line 83 in f309f59

if mediaType, ok := foundResponse.Content.Get(mediaTypeSting); ok {

libopenapi-validator/responses/validate_body.go

Line 101 in f309f59

} else if mediaType, ok := operation.Responses.Default.Content.Get(mediaTypeSting); ok {

The code Content.Get(mediaTypeSting) check if there is a schema with the exact content type in the operation spec.

Maybe the lib should loop over Content keys and compare with Content-Type from response, taking into account the wildcards.

func getMatchingMediaType(foundResponseContent, contentType string) (foundResponseContentMedia, bool){
  for media := foundResponseContent.First(); media != nil; media = media.Next() {
    mediatype, mediasubtype, _ := strings.Cut(media, "/")
    contenttype, contentsubtype, _ := strings.Cut(mediaTypeSting, "/")
    t := contenttype == mediatype || (contenttype == "*") || (mediatype == "*")
    st := mediasubtype == contentsubtype || mediasubtype == "*" || contentsubtype == "*"
    if t && st {
      return media, true
    }
  }
  return nil, false
}

if mediaType, ok := getMatchingMediaType(foundResponse.Content, mediaTypeSting); ok {
  ...

PS : the code is just a draft, not optimized, missing typing...

Edit : here is how kin-openapi handle it :
https://github.com/getkin/kin-openapi/blob/f5d61a7ecfdcfd776eeb7d121cbd4d8bb12c404f/openapi3/content.go#L64