Added base schema for Marshmallow dataclasses.

platypush/schemas/dataclasses/__init__.py

@@ -0,0 +1,56 @@
+from datetime import date, datetime
+from uuid import UUID
+
+from marshmallow import (
+    EXCLUDE,
+    Schema,
+    fields,
+    post_dump,
+)
+
+from .. import Date, DateTime
+
+
+class DataClassSchema(Schema):
+    """
+    Base schema class for data classes that support Marshmallow schemas.
+    """
+
+    TYPE_MAPPING = {
+        date: Date,
+        datetime: DateTime,
+        UUID: fields.UUID,
+    }
+
+    # pylint: disable=too-few-public-methods
+    class Meta:
+        """
+        Exclude unknown fields.
+        """
+
+        unknown = EXCLUDE
+
+    def _get_field(self, key: str) -> fields.Field:
+        """
+        Returns the matching field by either name or data_key.
+        """
+        if key in self.fields:
+            return self.fields[key]
+
+        matching_fields = [f for f in self.fields.values() if key == f.data_key]
+
+        assert (
+            len(matching_fields) == 1
+        ), f'Could not find field {key} in {self.__class__.__name__}'
+
+        return matching_fields[0]
+
+    @post_dump
+    def post_dump(self, data: dict, **__) -> dict:
+        # Use data_key parameters only for load
+        new_data = {}
+        for key, value in data.items():
+            field = self._get_field(key)
+            new_data[field.name if field.data_key is not None else key] = value
+
+        return new_data