Simple m[] string array in: query can't seem to work with both SwaggerUI and CastAndValidate

[degray]

Hello,

Looking for suggestions on where I'm going wrong.

Context, migrating to open_api_spex from phoenix_swagger. In phoenix_swagger the parameter had to be named m[] for everything to work. Using {:open_api_spex, "~> 3.16"}

First off, thank you for the library. So far the migration has been relatively painless with the exception of getting our m[] array query params to work.

There doesn't seem to be a simple way to get a Phoenix formatted query string array to work with both CastAndValidate and the SwaggerUI plug. Getting either to work seems to break the other one.

Taking this simple mock operation as an example:

  operation :get,
    summary: "Returns something",
    parameters:
      [ "m": [ in: :query, "description", required: true, schema: %Schema{type: :array, items: %Schema{type: :string}} ] ],
    responses: [
      ok: {"The return value", "text/plain", %Schema{ type: :string }} # Just left this as a string for simplicity but would really be a schema
    ]

That operation will happily take ?m[]=string1&m[]=string2 and validate properly w/ CastAndValidate. Problem is that if you use OpenApiSpex.Plug.SwaggerUI and use Try it out SwaggerUI will try to send it as ?m=string2&m=string2 without the square brackets which results in the following validation error from CastAndValidate.

{
  "errors": [
    {
      "detail": "Invalid array. Got: string",
      "source": {
        "pointer": "/m"
      },
      "title": "Invalid value"
    }
  ]
}

Changing it to "m[]" as the name will get SwaggerUI to send it in properly as ?m[]=string2&m[]=string2 but if you leave the CastAndValidate plug in you'll end up with the following error (removing the plug allows it to work)

{
  "errors": [
    {
      "detail": "Unexpected field: m",
      "source": {
        "pointer": "/m"
      },
      "title": "Invalid value"
    }
  ]
}

I assume I'm missing something here as I believe a simple query string based string array should be possible but I couldn't find an example of one anywhere in the docs without another parent :object surrounding it. Also couldn't find much in the Swagger docs or threads other than suggestions to rename the parameter to m[].

[degray]

Upon further investigation it looks like this is being caused by Phoenix behaviour on item[] query string values vs CastAndValidates behaviour. CastAndValidate will complain that m is an unexpected field when the field is named m[] as Phoenix will transform that to a list with the name m in params which doesn't match the name of m[]. Additional handling of arrays in query params for CastAndValidate is likely required to make this work without workarounds. I'll see if I can put together a PR for review for that in the future. For now we've got around it by naming the param m (so that CastAndValidate works) and then creating our own RenderSpec plug that can output the spec with the square brackets appended on in: :query arrays. Quite ugly I'll admit but currently functional for both validation and SwaggerUI (or anything else that would consume the OpenApiSpec and generate code for example).

[roryfahy]

@degray I'm running into the same issue here. any chance you could share a gist of that renderspec?

[roryfahy]

Also if you're still interested in putting a pr together, I'd be happy to pair on it sometime if you'd like. I've been meaning to give back to this project for a while.