Fix multitype enum validation inside an allOf

[ugexe]

Fixes regression starting in v2.00 where an enum containing a type constraint of ["string","null"] would not accept return values ( from Mojolicious::Plugin::OpenAPI ) of undef as valid if inside an allOf.

[ugexe]

There is probably a better fix than this PR, but hopefully this helps demonstrate its goal. Maybe the solution even belongs in Mojolicious::Plugin::OpenAPI?

Note I have not had time to construct a test, although this PR does pass current tests. Below is an example of the OpenAPI spec which allows a return value of attributes : 'null' in 1.08 but not in 2.00 or 2.01.

{
  "definitions": {
    "stipulation" : {
      "title" : "Data",
      "type" : "object",
      "allOf" : [
        {
          "$ref" : "#/definitions/metadata"
        },
        {
          "type" : "object",
          "properties" : {
            "name" : {
              "type" : "string"
            }
          }
        }
      ]
    },
    "metadata" : {
      "title" : "Metadata",
      "type" : "object",
      "properties" : {
        "attributes" : {
          "type" : ["string","null"],
          "enum" : ["foo", "bar","null"]
        }
      }
    }
  }
}

[jhthorsen]

Are you sure "enum":["foo","bar","null"] is right? I thought you had to have "enum":["foo","bar",null]

I don't get why you would have both enum and type...

[ugexe]

Having both enum and type has ( or was ) the only way to get an enumeration to accept both string values or null. Additionally it had to be a quoted null for the app to work properly ( writen approximately 1.5 years ago ), at least up to JV@1.08

[jhthorsen]

But "null" isn't the same as null, don't you agree..?

[ugexe]

https://github.com/jhthorsen/mojolicious-plugin-openapi/blob/5a0f0a2538b79e752f6d8db2b4ed55b7c0aedf31/t/empty-string.t#L43

"schema": {"type": ["null", "string"]}

[jhthorsen]

type values needs to be quoted, enum values does not. Pretty sure the old code was simply broken, and your code is "confused" now that it is fixed.

[ugexe]

So I just applied your advice and removed the type and changed "null" to null inside the enum, and the app works with the newer JSON::Validator.

I don't remember why we had to do that odd type/enum combo originally ( I remember wondering why we had to do it that way, but without time to investigate ). If I re-encounter the situation I will revisit this with additional info, but hopefully the cause was simply inadvertently fixed by other updates somewhere.

[jhthorsen]

Glad it worked out for you 👍

[ugexe]

So the reason we had quoted nulls and the extra type info was because swagger-ui 2.x does not work otherwise. It does work with swagger-ui 3.x though, so all is good.