(feat) Support for Pydantic field alias and serialization_alias

dataclasses_avroschema/fields/base.py

@@ -9,6 +9,7 @@
 from typing_extensions import get_args
 
 from dataclasses_avroschema import utils
+from dataclasses_avroschema.fields.field_utils import ensure_null_first
 
 p = Inflector()
 
@@ -78,7 +79,8 @@ def render(self) -> OrderedDict:
                 * tuple, he OrderedDict will contains the key symbols inside type
                 * dict, he OrderedDict will contains the key values inside type
         """
-        template = OrderedDict(self.get_metadata() + [("name", self.name), ("type", self.get_avro_type())])
+        avro_type = ensure_null_first(self.get_avro_type())
+        template = OrderedDict(self.get_metadata() + [("name", self.name), ("type", avro_type)])
         default = self.get_default_value()
 
         if default is not dataclasses.MISSING:
@@ -120,8 +122,7 @@ def to_dict(self) -> dict:
         return dict(self.render())
 
     @abc.abstractmethod
-    def get_avro_type(self) -> typing.Any:
-        ...  # pragma: no cover
+    def get_avro_type(self) -> typing.Any: ...  # pragma: no cover
 
     def fake(self) -> typing.Any:
         return None

dataclasses_avroschema/fields/field_utils.py

@@ -1,5 +1,6 @@
 import datetime
 import enum
+import typing
 import uuid
 
 from dataclasses_avroschema import types
@@ -97,3 +98,11 @@
     datetime.datetime: {"type": LONG, "logicalType": TIMESTAMP_MILLIS},
     uuid.uuid4: {"type": STRING, "logicalType": UUID},
 }
+
+
+def ensure_null_first(avro_type: typing.Any) -> typing.Any:
+    """Ensures null appears first in avro_type, if present."""
+    if not isinstance(avro_type, list) or NULL not in avro_type:
+        return avro_type
+
+    return [NULL] + [atype for atype in avro_type if atype != NULL]

dataclasses_avroschema/fields/fields.py

@@ -18,6 +18,7 @@
 )
 from dataclasses_avroschema.exceptions import InvalidMap
 from dataclasses_avroschema.faker import fake
+from dataclasses_avroschema.fields.field_utils import ensure_null_first
 from dataclasses_avroschema.utils import is_pydantic_model
 
 from . import field_utils
@@ -211,7 +212,7 @@ def generate_items_type(self) -> typing.Any:
                 parent=self.parent,
             )
 
-        self.items_type = self.internal_field.get_avro_type()
+        self.items_type = ensure_null_first(self.internal_field.get_avro_type())
 
 
 @dataclasses.dataclass

dataclasses_avroschema/pydantic/parser.py

@@ -18,6 +18,16 @@ def get_field_metadata(field_info: FieldInfo) -> dict[str, typing.Any]:
         )
         if field_info.description:
             metadata["doc"] = field_info.description  # type: ignore
+
+        aliases = set(metadata.get("aliases", []))
+
+        if field_info.alias:
+            aliases.add(field_info.alias)
+        if field_info.serialization_alias:
+            aliases.add(field_info.serialization_alias)
+        if aliases:
+            metadata["aliases"] = list(aliases)
+
         return metadata
 
     def parse_fields(self, exclude: typing.List) -> typing.List[Field]:

tests/schemas/pydantic/test_pydantic.py

@@ -91,6 +91,35 @@ class User(AvroBaseModel):
     assert User.avro_schema() == json.dumps(expected_schema)
 
 
+def test_pydantic_record_schema_with_aliases():
+    class User(AvroBaseModel):
+        foo: str = Field(alias="FOO")
+        bar: str = Field(serialization_alias="BAR")
+
+    expected_schema = {
+        "type": "record",
+        "name": "User",
+        "fields": [
+            {"aliases": ["FOO"], "name": "foo", "type": "string"},
+            {"aliases": ["BAR"], "name": "bar", "type": "string"},
+        ],
+    }
+    assert User.avro_schema() == json.dumps(expected_schema)
+
+
+def test_pydantic_record_schema_null_first():
+    class User(AvroBaseModel):
+        foo: typing.Optional[typing.List[typing.Optional[str]]]
+
+    expected_schema = {
+        "type": "record",
+        "name": "User",
+        "fields": [{"name": "foo", "type": ["null", {"type": "array", "items": ["null", "string"], "name": "foo"}]}],
+    }
+
+    assert User.avro_schema() == json.dumps(expected_schema)
+
+
 def test_pydantic_record_schema_complex_types(user_advance_avro_json, color_enum):
     class UserAdvance(AvroBaseModel):
         name: str