Enable Time and DateTime serialization (#69)

* Enable Time and DateTime serialization

* Fix formatting issues

* Improve datetime serialization test

* Use UTC Z designator in DateTime serialization

* Support null in time serialization

* Raise AssertionError on unexpected time-type

* Allow return type None in BaseFormat.serialize

Author: rbw

tests/test_schemas.py

@@ -5,6 +5,7 @@
 import pytest
 
 import typesystem
+import typesystem.formats
 
 
 class Person(typesystem.Schema):
@@ -148,17 +149,54 @@ def test_schema_missing_getattr():
         assert tshirt["missing"]
 
 
-def test_schema_format_serialization():
+def test_schema_date_serialization():
     class BlogPost(typesystem.Schema):
         text = typesystem.String()
         created = typesystem.Date()
+        modified = typesystem.Date(allow_null=True)
 
     post = BlogPost(text="Hi", created=datetime.date.today())
 
     data = dict(post)
 
     assert data["text"] == "Hi"
     assert data["created"] == datetime.date.today().isoformat()
+    assert data["modified"] is None
+
+
+def test_schema_time_serialization():
+    class MealSchedule(typesystem.Schema):
+        guest_id = typesystem.Integer()
+        breakfast_at = typesystem.Time()
+        dinner_at = typesystem.Time(allow_null=True)
+
+    guest_id = 123
+    breakfast_at = datetime.time(hour=10, minute=30)
+    schedule = MealSchedule(guest_id=guest_id, breakfast_at=breakfast_at)
+
+    assert typesystem.formats.TIME_REGEX.match(schedule["breakfast_at"])
+    assert schedule["guest_id"] == guest_id
+    assert schedule["breakfast_at"] == breakfast_at.isoformat()
+    assert schedule["dinner_at"] is None
+
+
+def test_schema_datetime_serialization():
+    class Guest(typesystem.Schema):
+        id = typesystem.Integer()
+        name = typesystem.String()
+        check_in = typesystem.DateTime()
+        check_out = typesystem.DateTime(allow_null=True)
+
+    guest_id = 123
+    guest_name = "Bob"
+    check_in = datetime.datetime.now(tz=datetime.timezone.utc)
+    guest = Guest(id=guest_id, name=guest_name, check_in=check_in)
+
+    assert typesystem.formats.DATETIME_REGEX.match(guest["check_in"])
+    assert guest["id"] == guest_id
+    assert guest["name"] == guest_name
+    assert guest["check_in"] == check_in.isoformat()[:-6] + "Z"
+    assert guest["check_out"] is None
 
 
 def test_schema_decimal_serialization():

typesystem/formats.py

@@ -37,7 +37,7 @@ def is_native_type(self, value: typing.Any) -> bool:
     def validate(self, value: typing.Any) -> typing.Union[typing.Any, ValidationError]:
         raise NotImplementedError()  # pragma: no cover
 
-    def serialize(self, obj: typing.Any) -> str:
+    def serialize(self, obj: typing.Any) -> typing.Union[str, None]:
         raise NotImplementedError()  # pragma: no cover
 
 
@@ -61,7 +61,12 @@ def validate(self, value: typing.Any) -> datetime.date:
         except ValueError:
             raise self.validation_error("invalid")
 
-    def serialize(self, obj: typing.Any) -> str:
+    def serialize(self, obj: typing.Any) -> typing.Union[str, None]:
+        if obj is None:
+            return None
+
+        assert isinstance(obj, datetime.date)
+
         return obj.isoformat()
 
 
@@ -89,8 +94,13 @@ def validate(self, value: typing.Any) -> datetime.time:
         except ValueError:
             raise self.validation_error("invalid")
 
-    # def serialize(self, obj: typing.Any) -> str:
-    #     return obj.isoformat()
+    def serialize(self, obj: typing.Any) -> typing.Union[str, None]:
+        if obj is None:
+            return None
+
+        assert isinstance(obj, datetime.time)
+
+        return obj.isoformat()
 
 
 class DateTimeFormat(BaseFormat):
@@ -130,11 +140,18 @@ def validate(self, value: typing.Any) -> datetime.datetime:
         except ValueError:
             raise self.validation_error("invalid")
 
-    # def serialize(self, obj: typing.Any) -> str:
-    #     value = value.isoformat()
-    #     if value.endswith('+00:00'):
-    #         value = value[:-6] + 'Z'
-    #     return value
+    def serialize(self, obj: typing.Any) -> typing.Union[str, None]:
+        if obj is None:
+            return None
+
+        assert isinstance(obj, datetime.datetime)
+
+        value = obj.isoformat()
+
+        if value.endswith("+00:00"):
+            value = value[:-6] + "Z"
+
+        return value
 
 
 class UUIDFormat(BaseFormat):