Adding schema for typing.Final (#9)

Author: giograno

src/py_avro_schema/_schemas.py

@@ -33,6 +33,7 @@
     Annotated,
     Any,
     Dict,
+    Final,
     ForwardRef,
     List,
     Literal,
@@ -378,6 +379,31 @@ def data(self, names: NamesType) -> JSONType:
         return self.literal_value_schema.data(names=names)
 
 
+@register_schema
+class FinalSchema(Schema):
+    """An Avro schema for Python ``typing.Final``"""
+
+    def __init__(self, py_type: Type, namespace: Optional[str] = None, options: Option = Option(0)):
+        """An Avro schema for Python ``typing.Final``"""
+        super().__init__(py_type, namespace, options)
+        py_type = _type_from_annotated(py_type)
+        try:
+            real_type = get_args(py_type)[0]
+        except IndexError:
+            raise TypeError("Can't generate Avro schema from Python typing.Final without a type parameter")
+        self.real_schema = _schema_obj(real_type, namespace=namespace, options=options)
+
+    def data(self, names: NamesType) -> JSONType:
+        """Return the schema data"""
+        return self.real_schema.data(names=names)
+
+    @classmethod
+    def handles_type(cls, py_type: Type) -> bool:
+        """Whether this schema class can represent a given Python class"""
+        py_type = _type_from_annotated(py_type)
+        return get_origin(py_type) is Final or py_type is Final
+
+
 @register_schema
 class DictAsJSONSchema(Schema):
     """An Avro string schema representing a Python Dict[str, Any] or List[Dict[str, Any]] assuming JSON serialization"""

tests/test_plain_class.py

@@ -10,7 +10,7 @@
 # specific language governing permissions and limitations under the License.
 
 import re
-from typing import Annotated
+from typing import Annotated, Final
 
 import pytest
 
@@ -160,3 +160,22 @@ def test_type_aliases_future():
 
     expected = {"fields": [{"name": "name", "type": "string"}], "name": "PyClass", "type": "record"}
     assert_schema(PyClass, expected)
+
+
+def test_typing_final():
+
+    class PyType:
+        var: Final[str]
+        field: Final[dict[str, int]]
+
+        def __init__(self):
+            self.var = "Hello World"
+            self.field = {"John": 123}
+
+    expected = {
+        "fields": [{"name": "var", "type": "string"}, {"name": "field", "type": {"type": "map", "values": "long"}}],
+        "name": "PyType",
+        "type": "record",
+    }
+
+    assert_schema(PyType, expected)