bug with items array

[andrejlevkovitch]

For tuple validation json schema allows usage of items keyword as an array, for example like here:

{
  "type": "array",
  "items": [
    {
      "$comment": "some comment",
      "type": "number"
    },
    {
      "type": "string"
    }
  ]
}

Also, we can use it in $defs too, like here:

{
  "type": "object",
  "properties": {
    "element": {
      "$ref": "#/$defs/element"
    }
  },
  "$defs": {
    "element": {
      "type": "array",
      "items": [
        {
          "type": "number"
        },
        {
          "type": "string"
        }
      ]
    }
  }
}

And that works perfectly with the library. But if I put $comment inside of one of the items, then I have exception:

cannot use operator[] with a string argument with array

So, that schema will throw the exception when you try to set it to validator

{
  "type": "object",
  "properties": {
    "element": {
      "$ref": "#/$defs/element"
    }
  },
  "$defs": {
    "element": {
      "type": "array",
      "items": [
        {
          "$comment": "some comment",
          "type": "number"
        },
        {
          "type": "string"
        }
      ]
    }
  }
}

Looks like only $comment keyword doesn't work properly in that context

[andrejlevkovitch]

I traced the issue to that line

[andrejlevkovitch]

seems that there are a problem with indexing - it tries to use an array as object and uses array index as object key

[andrejlevkovitch]

probably it is related to that comment:

json-schema-validator/src/json-validator.cpp

Lines 213 to 216 in 08d8a52

	// need to create an object for each reference-token in the
	// JSON-Pointer When not existing, a stringified integer reference
	// token (e.g. "123") in the middle of the pointer will be
	// interpreted a an array-index and an array will be created.

but I can not understand what that means. Is there a reason why it doesn't use json pointer directly?

[andrejlevkovitch]

If I understood everything correctly, the that pr should fix the issue

[pboettch]

So, it seems there is a bug with the handling of unknown keywords. Your schema shows that.

But why we have the unknown keyword handling getting involved here? Because $defs is something from the 2020-draft of json-schema not directly supported by this library. For the draft7-version it should be definitions. This is something to be taking into consideration in the analysis of this bug.

[andrejlevkovitch]

Yeah, that is fair. I'm not sure what I should do with that issue then... I mean should I close it or keep it?

[pboettch]

Well, it is still a bug with the unknown keyword handling, I'd need a better explanation as to why this happens before merging your PR.

[pboettch]

The errors wasn't the $comment field but a nested schema in an array of schemas in an unknown-keyword.

Your fix was correct and elegant: using a json-pointer to resolve the direct sub-keyword instead of find. This works for arrays and objects. Thanks for contributing.