UI sends multipart content even though API specifies application/json

[dblock]

Coming from artsy/doppler#142 with swagger-ui version: 3.19.4.

API specification is https://api.artsy.net/api/docs, which has

produces: [
"application/hal+json",
"application/json"
],

and all APIs say consumes with application/json.

The "Try me" UI POSTs multipart data while specifying JSON in content type, resulting in an error from our API.

  "type": "other_error",
  "message": "\nProblem:\n  message body does not match declared format\nResolution:\n  when specifying application/json as content-type, you must pass valid application/json in the request's 'body' ",

The curl code is incorrect too.

curl -X POST "http://localhost:3000/api/applications" -H "accept: application/json" -H "Content-Type: application/json" -H "X-Access-Token: ..." -d "name=test"

Reading the code ... is this because my fields have in: "formData" instead of in: "body"?

That seems still weird. If the content type required is JSON, shouldn't everything be JSON?

[shockey]

Hey @dblock!

It looks like your definition is describing all of your parameters as in: formData, which is why you're seeing url encoded values.

If you load your definition into Swagger Editor, you'll see a couple dozen errors that look like this:

Semantic error: Operations with Parameters of "in: formData" must include "application/x-www-form-urlencoded" or "multipart/form-data" in their "consumes" property.

---

Your POST /api/applications parameter currently looks like this:

      parameters:
        - in: formData
          name: name
          description: Application name.
          type: string
          required: true

If you want JSON, you should change in: formData to in: body to avoid url encoding, change type: string to type: object, and use properties to describe the JSON object you'd like to send. You'll also have to move type and properties under schema, since you're describing a body parameter.

For example:

      parameters:
        - in: body
          name: name
          description: Application name.
          required: true
          schema:
            type: object
            properties:
              name:
                type: string

This will give you a curl output that looks like this:

curl -X POST "http://api.artsy.net/api/applications" -H "accept: application/json" -H "Content-Type: application/json" -d "{ \"name\": \"string\"}"

Hope this helps!

[dblock]

Thanks. This is pretty clear. Now I have to figure out why we're defaulting primitive types into formData in grape-swagger, ruby-grape/grape-swagger#721

[shockey]

@dblock glad I could help! 😄

Note that I suggested using type: object. IMO, describing JSON as type: string is an antipattern (even though it's technically allowed) since you're missing out on a lot of the tooling ergonomics around object types and JSON.

[dblock]

Right. I meant each field is a string, but the whole thing is an object. When monkey patched as in ruby-grape/grape-swagger#721 I get this and everything works.