schema can cause infinite recursion

[rogpeppe]

Parsing a recursive schema not from a URL can cause infinite recursion.

Here is a repro example. Watch out, it will tank your computer until it runs out of stack space. Putting a print inside parseSchema will cause it to be more friendly.

package main

import (
    "encoding/json"
    "log"

    "github.com/binary132/gojsonschema"
)

func main() {
    var schema map[string]interface{}
    err := json.Unmarshal(data, &schema)
    if err != nil {
        log.Fatalf("cannot unmarshal schema definition: %v", err)
    }

    _, err = gojsonschema.NewJsonSchemaDocument(schema)
    if err != nil {
        log.Fatalf("cannot parse schema definition: %v", err)
    }
}

var data = []byte(`
{
    "definitions": {
        "schemaArray": {
            "items": {
                "$ref": "#"
            },
            "type": "array"
        }
    },
    "properties": {
        "items": {
            "$ref": "#/definitions/schemaArray"
        },
        "not": {
            "$ref": "#"
        }
    },
    "type": "object"
}
`)