Repository: marcosschroh/dataclasses-avroschema

Issue:
NameSpaceRequiredException when reusing child class
Hi there! First off, thank you for the fantastic library. 🍰 

I'm running into the following issue in a migration to dataclasess-avroschema:

```python
from dataclasses_avroschema.avrodantic import AvroBaseModel


class ChildA(AvroBaseModel):
    id: int


class ChildB(AvroBaseModel):
    id: int


class Parent(AvroBaseModel):
    x: ChildA | ChildB
    y: ChildA | ChildB

    class Meta:
        namespace = "com.example"


d = Parent(x=ChildA(id=42), y=ChildB(id=43))
print(d.serialize(serialization_type="avro-json"))
```
```
  File "C:\Python3.11\Lib\site-packages\dataclasses_avroschema\fields.py", line 773, in get_avro_type
    raise NameSpaceRequiredException(field_type=self.type, field_name=self.name)
dataclasses_avroschema.exceptions.NameSpaceRequiredException: Required namespace in Meta for type <class '__main__.ChildA'>. The field y is using an exiting type
```

Removing `y` fixes the issue and correctly produces:
```json
{"x": {"com.example.ChildA": {"id": 42}}}
```

The problem seems to be that `exist_type` turns `True`, but I don't understand enough of the codebase to know what the correct  fix is. 😃 

Discussion:
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on branch [`gh-pages`](https://github.com/marcosschroh/dataclasses-avroschema/tree/gh-pages) at 2023-03-06 14:05 UTC
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Patch:
diff --git a/dataclasses_avroschema/exceptions.py b/dataclasses_avroschema/exceptions.py
index f694907..079718a 100644
--- a/dataclasses_avroschema/exceptions.py
+++ b/dataclasses_avroschema/exceptions.py
@@ -1,22 +1,6 @@
 import typing
 
 
-class NameSpaceRequiredException(Exception):
-    def __init__(self, field_type: typing.Any, field_name: str) -> None:
-        self.field_type = field_type
-        self.field_name = field_name
-
-    def __repr__(self) -> str:
-        class_name = self.__class__.__name__
-        return f"{class_name} {self.field_name},{self.field_type}"
-
-    def __str__(self) -> str:
-        return (  # pragma: no cover
-            f"Required namespace in Meta for type {self.field_type}. "
-            f"The field {self.field_name} is using an exiting type"
-        )
-
-
 class InvalidMap(Exception):
     def __init__(self, field_name: str, key_type: typing.Any) -> None:
         self.field_name = field_name
diff --git a/dataclasses_avroschema/fields.py b/dataclasses_avroschema/fields.py
index 74a22a9..fb4d62a 100644
--- a/dataclasses_avroschema/fields.py
+++ b/dataclasses_avroschema/fields.py
@@ -20,7 +20,7 @@ from pytz import utc
 from dataclasses_avroschema import schema_generator, serialization, types, utils
 
 from . import field_utils
-from .exceptions import InvalidMap, NameSpaceRequiredException
+from .exceptions import InvalidMap
 from .types import JsonDict
 
 PY_VER = sys.version_info
@@ -483,8 +483,9 @@ class EnumField(BaseField):
         else:
             namespace = metadata.get("namespace")
             if namespace is None:
-                raise NameSpaceRequiredException(field_type=self.type, field_name=name)
-            return f"{namespace}.{name}"
+                return name
+            else:
+                return f"{namespace}.{name}"
 
     def get_default_value(self) -> typing.Union[str, dataclasses._MISSING_TYPE, None]:
         if self.default == types.MissingSentinel:
@@ -770,8 +771,9 @@ class RecordField(BaseField):
             record_type["name"] = name
         else:
             if metadata.namespace is None:
-                raise NameSpaceRequiredException(field_type=self.type, field_name=self.name)
-            record_type = f"{metadata.namespace}.{name}"
+                record_type = name
+            else:
+                record_type = f"{metadata.namespace}.{name}"
 
         if self.default is None:
             return [field_utils.NULL, record_type]
diff --git a/docs/complex_types.md b/docs/complex_types.md
index 8e7f9b0..54cb245 100644
--- a/docs/complex_types.md
+++ b/docs/complex_types.md
@@ -71,7 +71,8 @@ User.avro_schema()
 
 ### Repeated Enums
 
-Sometimes we have cases where an `Enum` is used more than once with a particular class, for those cases, you `MUST` define the namespace in order to generate a valid `avro schema`
+Sometimes we have cases where an `Enum` is used more than once with a particular class, for those cases the same `type` is used in order to generate a valid schema.
+It is a good practice but *NOT* neccesary to a define the `namespace` on the repeated `type`.
 
 ```python
 import enum
@@ -123,7 +124,7 @@ resulting in
       "name": "optional_distance",
       "type": [
         "null",
-        "trip.TripDistance"
+        "trip.TripDistance"  // using the namespace and the TripDistance type
       ],
       "default": null
     }
@@ -132,9 +133,6 @@ resulting in
 }
 ```
 
-!!! warning
-    If you do not specify the `namespace` in the `Enum` the exception `NameSpaceRequiredException` is raised
-
 ## Arrays
 
 ```python title="Array example"
diff --git a/docs/good_practices.md b/docs/good_practices.md
index 5a8f5e2..c632df3 100644
--- a/docs/good_practices.md
+++ b/docs/good_practices.md
@@ -1,6 +1,6 @@
-## Streaming
+# Streaming
 
-### Schema server and AvroModel
+## Schema server and AvroModel
 
 First, let's clarify what a schema server is: It is a `central place/repository` that contains schemas with formats like `avro`, `json` or `protobuf`, with the purpose of exposing them through an `API`, so applications can access them and `serialize/deserialize` events. The schema server could have a `RESTful` interface so tasks like `create`, `delete` `get` schemas can be performed easily. 
 
@@ -29,8 +29,7 @@ class User(AvroModel):
 
 The purpose of the `schema_id` is to give a fast notion what the model is representing. Also, could be used as `documentation`
 
-
-### Include event metadata
+## Include event metadata
 
 `avro schemas` are used widely in `streaming` to `serialize` events, and with `dataclasses-avroschemas` it is straigtforward. Once 
 that you have the event, it is a good practice to also add the `event metadata` at the moment of `producing` so `consumers` will know what to do.
@@ -56,7 +55,7 @@ class User(AvroModel):
     money: float = 100.3
 
     class Meta:
-        schema_id = "https://my-schema-server/users/schema.avsc" # or in a Concluent way: https://my-schema-server/schemas/ids/{int: id}
+        schema_id = "https://my-schema-server/users/schema.avsc" # or in a Confluent way: https://my-schema-server/schemas/ids/{int: id}
 
 
 async def produce():
@@ -80,4 +79,14 @@ async def produce():
 
 if __name__ == "__main__":
     asyncio.run(produce)
-```
\ No newline at end of file
+```
+
+## Define Namespaces
+
+When there are types that are used more than once in a schema, for example `records` and `enums` it is a good practice to define `namespace` for the repeated type.
+This will allow you to identify more easily the `types`, specially if you have all the schemas in a `schema server` like `confluent`.
+
+Uses cases:
+
+- [Reusing types with records](https://marcosschroh.github.io/dataclasses-avroschema/schema_relationships/#avoid-name-collision-in-multiple-relationships)
+- [Reusing types with enums](https://marcosschroh.github.io/dataclasses-avroschema/complex_types/#repeated-enums)
diff --git a/docs/model_generator.md b/docs/model_generator.md
index cee7009..acec709 100644
--- a/docs/model_generator.md
+++ b/docs/model_generator.md
@@ -11,7 +11,7 @@ The rendered result is a string that contains the proper identation, so the resu
     In future releases it will be possible to generate models for other programming langagues like `java` and `rust`
 
 !!! note
-    You can also use [dc-avro](https://github.com/marcosschroh/dc-avro)d to generate the models from the command line
+    You can also use [dc-avro](https://github.com/marcosschroh/dc-avro) to generate the models from the command line
 
 ## Usage
 
diff --git a/docs/schema_relationships.md b/docs/schema_relationships.md
index 9f4bbba..39cf3df 100644
--- a/docs/schema_relationships.md
+++ b/docs/schema_relationships.md
@@ -278,11 +278,10 @@ User.avro_schema()
 
 ## Avoid name collision in multiple relationships
 
-Sometimes we have relationships where a class is related more than once with a particular class,
-and the name for the nested schemas must be different, otherwise we will generate an invalid `avro schema`.
-For those cases, you *MUST* define the `namespace`.
+Sometimes we have relationships where a class is related more than once with a particular class.
+In those cases, the `predifne` type is used in order to generate a valid schema. It is a good practice but *NOT* neccesary to a define the `namespace` on the repeated `type`.
 
-```python title="Avoiding name collision example"
+```python title="Repetead types"
 from dataclasses import dataclass
 from datetime import datetime
 import json
@@ -296,7 +295,7 @@ class Location(AvroModel):
     longitude: float
 
     class Meta:
-        namespace = "types.location_type"
+        namespace = "types.location_type"  # Good practise to use `namespaces`
 
 @dataclass
 class Trip(AvroModel):
@@ -333,7 +332,7 @@ Trip.avro_schema()
       "type": {"type": "long", "logicalType": "timestamp-millis"}
     },
     {
-      "name": "finish_location", "type": "types.location_type.Location"  // using the namespace
+      "name": "finish_location", "type": "types.location_type.Location"  // using the namespace and the Location type
     }
   ],
   "doc": "Trip(start_time: datetime.datetime, start_location: __main__.Location, finish_time: datetime.datetime, finish_location: __main__.Location)"


Test patch:
diff --git a/tests/schemas/test_fastavro_paser_schema.py b/tests/schemas/test_fastavro_paser_schema.py
index 81ae619..5c09b80 100644
--- a/tests/schemas/test_fastavro_paser_schema.py
+++ b/tests/schemas/test_fastavro_paser_schema.py
@@ -152,6 +152,19 @@ def test_one_to_one_repeated_schema():
     assert Trip.fake()
 
 
+def test_repeated_schema_without_namespace():
+    class Bus(AvroModel):
+        "A Bus"
+        engine_name: str
+
+    class UnionSchema(AvroModel):
+        "Some Unions"
+        bus_one: Bus
+        bus_two: Bus
+
+    parse_schema(UnionSchema.avro_schema_to_python())
+
+
 def test_one_to_one_repeated_schema_in_array():
     """
     Test relationship one-to-one with more than once schema
diff --git a/tests/schemas/test_schema.py b/tests/schemas/test_schema.py
index bde9754..9582de6 100644
--- a/tests/schemas/test_schema.py
+++ b/tests/schemas/test_schema.py
@@ -5,7 +5,7 @@ from dataclasses import dataclass
 import pytest
 from fastavro.validation import ValidationError
 
-from dataclasses_avroschema import AvroModel, exceptions
+from dataclasses_avroschema import AvroModel
 from dataclasses_avroschema.schema_definition import BaseSchemaDefinition
 from dataclasses_avroschema.types import JsonDict
 
@@ -123,20 +123,6 @@ def test_not_implementd_methods():
     assert msg == str(excinfo.value)
 
 
-def test_namespace_required():
-    class Bus(AvroModel):
-        "A Bus"
-        engine_name: str
-
-    class UnionSchema(AvroModel):
-        "Some Unions"
-        bus_one: Bus
-        bus_two: Bus
-
-    with pytest.raises(exceptions.NameSpaceRequiredException):
-        assert UnionSchema.avro_schema()
-
-
 def test_inherit_dataclass_missing_docs():
     @dataclass
     class BaseUser:
diff --git a/tests/schemas/test_schema_with_complex_types.py b/tests/schemas/test_schema_with_complex_types.py
index 1fa4f1b..d8d6755 100644
--- a/tests/schemas/test_schema_with_complex_types.py
+++ b/tests/schemas/test_schema_with_complex_types.py
@@ -9,7 +9,7 @@ import uuid
 import pytest
 from fastavro import parse_schema
 
-from dataclasses_avroschema import AvroModel, exceptions
+from dataclasses_avroschema import AvroModel
 from dataclasses_avroschema.types import JsonDict
 
 PY_VER = sys.version_info
@@ -155,7 +155,7 @@ def test_schema_with_new_unions_defaults_syntax(default_union_schema: JsonDict)
     assert User.avro_schema() == json.dumps(default_union_schema)
 
 
-def test_enum_namespace_required() -> None:
+def test_repeated_enum_without_namespace() -> None:
     class UserType(enum.Enum):
         BASIC = "Basic"
         PREMIUM = "Premium"
@@ -165,8 +165,7 @@ def test_enum_namespace_required() -> None:
         user_type: UserType
         user_type_optional: typing.Optional[UserType]
 
-    with pytest.raises(exceptions.NameSpaceRequiredException):
-        User.avro_schema()
+    parse_schema(User.avro_schema_to_python())
 
 
 # This is to explicitly test the behavior for a typing.Optional[T] field with no default