Stack overflow with recursive JSON schema

[Julien-Hanin]

Calling the validator on (some) recursive JSON schemas throws a StackOverflowError. I've tested this code

import java.nio.file.Files;
import java.nio.file.Path;
import java.util.List;

import io.confluent.kafka.schemaregistry.SchemaValidatorBuilder;
import io.confluent.kafka.schemaregistry.SimpleParsedSchemaHolder;
import io.confluent.kafka.schemaregistry.json.JsonSchema;

class Main {
  public static void main(String[] args) throws Exception {
    JsonSchema schema = new JsonSchema(new String(Files.readAllBytes(Path.of("SERVICE.json"))));
    new SchemaValidatorBuilder().canReadStrategy().validateLatest().validate(schema, List.of(new SimpleParsedSchemaHolder(schema)));
  }
}

with SERVICE.json being either

{
  "$schema" : "https://json-schema.org/draft/2020-12/schema",
  "$defs" : {
    "Permission" : {
      "type" : "object",
      "properties" : {
        "service" : {
          "$ref" : "#"
        }
      }
    }
  },
  "type" : "object",
  "properties" : {
    "permission" : {
      "$ref" : "#/$defs/Permission"
    }
  }
}

or even

{
  "$schema" : "https://json-schema.org/draft/2020-12/schema",
  "$defs" : {
    "Permission" : {
      "type" : "object",
      "properties" : {
        "service" : {
          "$ref" : "#"
        }
      }
    }
  },
  "type" : "object",
  "properties" : {
    "permission" : {
      "type" : "string"
    }
  }
}

This results in

Exception in thread "main" java.lang.IllegalArgumentException: Invalid JSON Schema
	at io.confluent.kafka.schemaregistry.json.JsonSchema.rawSchema(JsonSchema.java:399)
	at io.confluent.kafka.schemaregistry.json.JsonSchema.isBackwardCompatible(JsonSchema.java:671)
	at io.confluent.kafka.schemaregistry.SchemaValidatorBuilder.lambda$canReadStrategy$0(SchemaValidatorBuilder.java:51)
	at io.confluent.kafka.schemaregistry.SchemaValidatorBuilder.lambda$validateLatest$3(SchemaValidatorBuilder.java:92)
	at test.Main.main(Main.java:36)
Caused by: java.lang.StackOverflowError
	at java.base/java.util.LinkedHashMap$LinkedKeyIterator.<init>(LinkedHashMap.java:1045)
	at java.base/java.util.LinkedHashMap$LinkedKeySet.iterator(LinkedHashMap.java:700)
	at java.base/java.util.HashSet.iterator(HashSet.java:182)
	at com.github.erosb.jsonsKema.SchemaVisitor.visitChildren(SchemaVisitor.kt:142)
	at io.confluent.kafka.schemaregistry.json.schema.SchemaTranslator.visitChildren(SchemaTranslator.java:176)
	at io.confluent.kafka.schemaregistry.json.schema.SchemaTranslator.visitChildren(SchemaTranslator.java:105)
	at com.github.erosb.jsonsKema.SchemaVisitor.visitCompositeSchema(SchemaVisitor.kt:66)
	at io.confluent.kafka.schemaregistry.json.schema.SchemaTranslator.visitCompositeSchema(SchemaTranslator.java:185)

[Julien-Hanin]

This happens both on 7.9.2 and 8.0.0.