0.17: Infinite recursion in compilation

[audunhalland]

I have a test in my project for infinite data size. This was working well (i.e. not crashing) until the 0.17 upgrade. I'm using Draft202012 for the following schema:

{
  "allOf": [
    {
      "$ref": "#/$defs/1_1"
    }
  ],
  "unevaluatedProperties": false,
  "$defs": {
    "1_1": {
      "type": "object",
      "properties": {
        "b": {
          "allOf": [
            {
              "$ref": "#/$defs/1_2"
            }
          ],
          "unevaluatedProperties": false
        }
      },
      "required": [
        "b"
      ]
    },
    "1_2": {
      "type": "object",
      "properties": {
        "f": {
          "allOf": [
            {
              "$ref": "#/$defs/1_1"
            }
          ],
          "unevaluatedProperties": false
        }
      },
      "required": [
        "f"
      ]
    }
  }
}

I am no jsonschema expert, but I believe this is a valid schema that should accept no JSON documents, because of the required infinite size.

[tobz]

This is certainly related to my PR introducing support for unevaluatedProperties in #419.

Checking your schema in Hyperjump, it is indeed a valid configuration, and will only emit validation errors at a depth that is correlated with the input itself.

We could likely copy what the $ref validator itself does, which is to hold on to the relevant compilation context and lazily instantiate validator nodes as needed... which would allow for building the $ref-specific subvalidator used for unevaluatedProperties as deep as the input data needs it to be, without recursing infinitely right off the bat.

Definitely a hindsight on my part to not follow what $ref did from the beginning. I was already looking into another bug that I found with my work on unevaluatedProperties, so I'll see if I can fix this at the same time.