Combining schemas: "oneOf, anyOf, allOf and not" keywords support

[kroupacz]

Hello, in our project we need support for the OpenAPI 3 specification and we also would like to continue to use your library without creating our own "fork". Therefore I have prepared this "pull request" with support of "oneOf, anyOf, allOf and not" keywords. Details can be found here: https://swagger.io/docs/specification/data-models/oneof-anyof-allof-not/

Added:

• support for OAS3 "oneOf, anyOf, allOf and not" keywords
  • this functionality is reflected in the processing of "joi.when()" conditions, "joi.alternatives()" and "joi.array()"
• support for "switch" condition ( joi.when('x', { is: true, switch: { ... } }) )
• support for invalid method ( joi.string().invalid('A','B','C') )

Fixed:

• compatibility with @hapi/joi v16

Breaking changes:

• removed support for "swaggerIndex", because it is no longer needed due to added support of "oneOf, anyOf, allOf" keywords

Could be discussed:

• in case of "joi.when()" and "joi.alternatives()" the "joi.required()" is just implemented as a custom property option called "x-required", e.g. x-required: true. The final swagger definition will be valid and information about the possible mandatory properties will be retained
• or "required" properties could be added to "anyOf" array at "object" level, but it will not be clear to which specific subschema it belongs to. e.g.:

  {
  "type": "object",
  "properties": {
  "user_id": {
    "oneOf": [
      { "type" : "number" },
      { "type" : "string" }
    ]
  },
  "type": {
    "type" : "string",
    "oneOf": [
      { "enum" : ["A", "B"] },
      { "enum" : ["C", "D"] }
    ]
  },
  "name": {
    "type": "string"
  }
  },
  "anyOf": [
  { "required": [ "user_id" ] },
  { "required": ["type"] }
  ]
  }

• it could be also implemented like this:

  {
  "type": "object",
  "properties": {
  "user_id": {},
  "type": {},
  "name": {
    "type": "string"
  }
  },
  "allOf": [
  {
    "oneOf": [
      {
        "required": ["user_id"],
        "properties": {
          "user_id": {
            "type": "number"
          }
        }
      },
      {
        "required": ["user_id"],
        "properties": {
          "user_id": {
            "type": "string"
          }
        }
      }
    ]
  },
  {
    "oneOf": [
      {
        "required": ["type"],
        "properties": {
          "type": {
            "type": "string",
            "enum": ["A", "B"]
          }
        }
      },
      {
        "required": ["type"],
        "properties": {
          "type": {
            "type": "string",
            "enum": ["C", "D"]
          }
        }
      }
    ]
  } 
  ]
  }

  but it creates a lot of boilerplate code and from my point of view this kind of definition is not clearly displayed in Swagger UI

[Mairu]

Hi, thanks for the PR. I will have a look soon.

But I think you should add the additional supported joi functions to the readme. Perhaps even with a more detailed description if needed.

[kroupacz]

Thank you for your reply. I just updated "readme" and "changelog". In case of any question regarding my "pull request", do not hesitate to contact me.

[Mairu]

Thank you very much for the PR!