Support of References for AVRO Schemas

src/karapace/schema_models.py

@@ -5,7 +5,8 @@
 from __future__ import annotations
 
 from avro.errors import SchemaParseException
-from avro.schema import parse as avro_parse, Schema as AvroSchema
+from avro.name import Names as AvroNames
+from avro.schema import make_avsc_object, parse as avro_parse, Schema as AvroSchema
 from collections.abc import Collection, Mapping, Sequence
 from dataclasses import dataclass
 from jsonschema import Draft7Validator
@@ -30,6 +31,7 @@
 from typing import Any, cast, Final, final
 
 import hashlib
+import json
 import logging
 
 LOG = logging.getLogger(__name__)
@@ -153,6 +155,7 @@ def normalize_schema_str(
             except JSONDecodeError as e:
                 LOG.info("Schema is not valid JSON")
                 raise e
+
         elif schema_type == SchemaType.PROTOBUF:
             if schema:
                 schema_str = str(schema)
@@ -195,6 +198,29 @@ def schema(self) -> Draft7Validator | AvroSchema | ProtobufSchema:
         return parsed_typed_schema.schema
 
 
+def avro_resolve(schema_str: str, dependencies: Mapping[str, Dependency] | None = None) -> list:
+    """Resolve the given ``schema_str`` with ``dependencies`` to a list of schemas
+    sorted in an order where all referenced schemas are located prior to their referrers.
+
+    To support references in AVRO we iteratively merge all referenced schemas with current schema
+
+    """
+    schema_str = json_encode(json_decode(schema_str), compact=True, sort_keys=True)
+    stack: list[tuple[str, Mapping[str, Dependency] | None]] = [(schema_str, dependencies)]
+    merge: list = []
+
+    while stack:
+        current_schema_str, current_dependencies = stack.pop()
+        if current_dependencies:
+            stack.append((current_schema_str, None))
+            for dependency in reversed(current_dependencies.values()):
+                stack.append((dependency.schema.schema_str, dependency.schema.dependencies))
+        else:
+            merge.append(current_schema_str)
+
+    return merge
+
+
 def parse(
     schema_type: SchemaType,
     schema_str: str,
@@ -207,18 +233,33 @@ def parse(
 ) -> ParsedTypedSchema:
     if schema_type not in [SchemaType.AVRO, SchemaType.JSONSCHEMA, SchemaType.PROTOBUF]:
         raise InvalidSchema(f"Unknown parser {schema_type} for {schema_str}")
-
     parsed_schema: Draft7Validator | AvroSchema | ProtobufSchema
     if schema_type is SchemaType.AVRO:
         try:
+            if dependencies:
+                schemas_list = avro_resolve(schema_str, dependencies)
+                names = AvroNames(validate_names=validate_avro_names)
+                merged_schema = None
+                for schema in schemas_list:
+                    # Merge dep with all previously merged ones
+                    merged_schema = make_avsc_object(json.loads(schema), names)
+                merged_schema_str = str(merged_schema)
+            else:
+                merged_schema_str = schema_str
             parsed_schema = parse_avro_schema_definition(
-                schema_str,
+                merged_schema_str,
                 validate_enum_symbols=validate_avro_enum_symbols,
                 validate_names=validate_avro_names,
             )
+            return ParsedTypedSchema(
+                schema_type=schema_type,
+                schema_str=schema_str,
+                schema=parsed_schema,
+                references=references,
+                dependencies=dependencies,
+            )
         except (SchemaParseException, JSONDecodeError, TypeError) as e:
             raise InvalidSchema from e
-
     elif schema_type is SchemaType.JSONSCHEMA:
         try:
             parsed_schema = parse_jsonschema_definition(schema_str)
@@ -287,7 +328,6 @@ def __init__(
         dependencies: Mapping[str, Dependency] | None = None,
     ) -> None:
         self._schema_cached: Draft7Validator | AvroSchema | ProtobufSchema | None = schema
-
         super().__init__(
             schema_type=schema_type,
             schema_str=schema_str,

src/karapace/schema_reader.py

@@ -614,7 +614,19 @@ def _handle_msg_schema(self, key: dict, value: dict | None) -> None:
 
         parsed_schema: Draft7Validator | AvroSchema | ProtobufSchema | None = None
         resolved_dependencies: dict[str, Dependency] | None = None
-        if schema_type_parsed in [SchemaType.AVRO, SchemaType.JSONSCHEMA]:
+        if schema_type_parsed == SchemaType.AVRO:
+            try:
+                if schema_references:
+                    candidate_references = [reference_from_mapping(reference_data) for reference_data in schema_references]
+                    resolved_references, resolved_dependencies = self.resolve_references(candidate_references)
+                schema_str = json.dumps(json.loads(schema_str), sort_keys=True)
+            except json.JSONDecodeError as e:
+                LOG.warning("Schema is not valid JSON")
+                raise e
+            except InvalidReferences as e:
+                LOG.exception("Invalid AVRO references")
+                raise e
+        elif schema_type_parsed == SchemaType.JSONSCHEMA:
             try:
                 schema_str = json.dumps(json.loads(schema_str), sort_keys=True)
             except json.JSONDecodeError as exc:

src/karapace/schema_registry_apis.py

@@ -1051,7 +1051,7 @@ def _validate_references(
                 content_type=content_type,
                 status=HTTPStatus.BAD_REQUEST,
             )
-        if references and schema_type != SchemaType.PROTOBUF:
+        if references and schema_type != SchemaType.PROTOBUF and schema_type != SchemaType.AVRO:
             self.r(
                 body={
                     "error_code": SchemaErrorCodes.REFERENCES_SUPPORT_NOT_IMPLEMENTED.value,