"type" has to be singular by flattener code but can be an array by schema validation

[kddejong]

This is to track if we should support multiple types or fix the code in cloudformation-cli to support multiple types. Right now the flatenner will fail when doing the following. Additionally the schema allows for multiple types.

{
  "type": ["array", "object"],
  "properties": {
    "a": {}
  },
  "items": {
    "properties": {
      "b": {}
    }
  }
}

https://github.com/aws-cloudformation/cloudformation-cli/blob/f0e376989c1b5a106c97b25b78e98f46bdb5995f/src/rpdk/core/jsonutils/flattener.py#L19-L23

Schema definition: https://github.com/aws-cloudformation/cloudformation-resource-schema/blob/master/src/main/resources/schema/schema#L145-L155

{
    "type": {
      "anyOf": [
        { "$ref": "#/definitions/simpleTypes" },
        {
          "type": "array",
          "items": { "$ref": "#/definitions/simpleTypes" },
          "minItems": 1,
          "uniqueItems": true
        }
      ]
    }
}

[ericzbeard]

Are there any existing types that do this?

[kddejong]

Not if they are using the cloudformation-cli cause it would fail.

This shows up the most as a result of inline policies or definitions (like step functions).

"type": [
    "object",
    "string"
   ]

There are some other random multi types... none that specify array and objects together. In general the flattener is used in a lot of places in the cloudformation-cli and we make an assumption that we only support singular types.