additionalProperties check is "too aggresive"

[castarco]

Hi, I've found a strange error while using this library (v2.6). The additionalProperties check is behaving too aggressively, rejecting some "JSON" documents that (in theory, as far as I can see) should fit into the schema.

Here the (very simplified) schema (look into the estimator_node definition):

{
  "$schema": "http://json-schema.org/draft-07/schema#",

  "type": "object",
  "title": "Traffic Distribution Specification",
  "description": "Document describing how traffic is distributed across pipelines",

  "properties": {
    "schema_version": {
      "description": "Specifies the schema version used to validate the traffic distribution document: X, X.Y, X.Y.Z",
      "type": "string",
      "pattern": "^([1-9][0-9]*|0)(\\.([1-9][0-9]*|0)(\\.([1-9][0-9]*|0))?)?$"
    },
    "pipeline_parts": {
      "description": "Optional block to make easier grouping pipeline part definitions",
      "type": "object",
      "properties": {
        "estimators": {
          "type": "object",
          "additionalProperties": { "$ref": "#/definitions/estimator_node" },
          "required": []
        }
      },
      "required": []
    }
  },
  "dependencies": {},

  "definitions": {
    "estimator_node": {
      "type": "object",
      "properties": {
        "name": { "type": "string", "minLength": 3 },
        "type": { "type": "string" },
        "train_only": { "type": "boolean", "default": false },
        "params": { "type": "object", "properties": {}, "additionalProperties": true}
      },
      "required": ["name", "type"],
      "additionalProperties": false
    }
  }
}

As you can see, only name and type are required, while params and train_only are not required (but defined in the "properties" object). The validator does not complain in any case when I'm passing a params key to the validated objects, but it complains (incorrectly) when I pass a train_only key telling me that the additionalProperties directive does not allow me to use that key... when the JSON schema spec explicitly tells that the only forbidden keys are the ones not defined in the properties object.

Example of a YAML document (yeah, YAML, but this hasn't been a problem in many months) (I have removed parts of the YAML that contain business data):

schema_version: "2.0"

pipeline_parts:
  estimators:
    estimator_example:
      name: "estimator_example"
      type: "MyMagicEstimator"
      train_only: true  # This is the problematic key
      params:
        a: 1.0
        b: 0.0

[castarco]

Error on my side, of course.