Improve public API type annotations & fix unit test type errors (#248)

* chore: improve typing of functions returning AnyCloudEvent

kafka.conversion.from_binary() and from_structured() return
AnyCloudEvent type var according to their event_type argument, but when
event_type is None, type checkers cannot infer the return type. We now
use an overload to declare that the return type is http.CloudEvent when
event_type is None.

Previously users had to explicitly annotate this type when calling
without event_type. This happens quite a lot in this repo's
test_kafka_conversions.py — this fixes quite a few type errors like:

> error: Need type annotation for "result"  [var-annotated]

Signed-off-by: Hal Blackburn <hwtb2@cam.ac.uk>

* chore: type v1.Event chainable Set*() methods

The v1.Event self-returning Set*() methods like SetData() were returning
BaseEvent, which doesn't declare the same Set* methods. As a result,
chaining more than one Set* method would make the return type unknown.

This was causing type errors in test_event_pipeline.py.

The Set*() methods now return the Self type.

Signed-off-by: Hal Blackburn <hwtb2@cam.ac.uk>

* chore: fix type errors in tests

mypy was failing with lots of type errors in test modules. I've not
annotated all fixtures, mostly fixed existing type errors.

Signed-off-by: Hal Blackburn <hwtb2@cam.ac.uk>

* chore: allow non-dict headers types in from_http()

from_http() conversion function was requiring its headers argument to
be a typing.Dict, which makes it incompatible with headers types of http
libraries, which support features like multiple values per key.
typing.Mapping and even _typeshed.SupportsItems do not cover these
types. For example,
samples/http-image-cloudevents/image_sample_server.py was failing to
type check where it calls `from_http(request.headers, ...)`.

To support these kind of headers types in from_http(), we now define our
own SupportsDuplicateItems protocol, which is broader than
_typeshed.SupportsItems.

I've only applied this to from_http(), as typing.Mapping is OK for most
other methods that accept dict-like objects, and using this more lenient
interface everywhere would impose restrictions on our implementation,
even though it might be more flexible for users.

Signed-off-by: Hal Blackburn <hwtb2@cam.ac.uk>

* build: run mypy via tox

Tox now runs mypy on cloudevents itself, and the samples.

Signed-off-by: Hal Blackburn <hwtb2@cam.ac.uk>

* build(ci): run mypy in CI alongside linting

Signed-off-by: Hal Blackburn <hwtb2@cam.ac.uk>

* chore: fix minor mypy type complaint in samples

Signed-off-by: Hal Blackburn <hwtb2@cam.ac.uk>

* feat: use Mapping, not Dict for input arguments

Mapping imposes less restrictions on callers, because it's read-only and
allows non-dict types to be passed without copying them as dict(), or
passing dict-like values and ignoring the resulting type error.

Signed-off-by: Hal Blackburn <hwtb2@cam.ac.uk>

* chore: fix tests on py3.8

Tests were failing because the sanic dependency dropped support for
py3.8 in its current release. sanic is now pinned to the last compatible
version for py3.8 only.

Signed-off-by: Hal Blackburn <hwtb2@cam.ac.uk>

* feat: support new model_validate_json() kwargs

Pydantic added by_alias and by_name keyword arguments to
BaseModel.model_validate_json in 2.11.1:

pydantic/pydantic@acb0f10

This caused mypy to report that that the Pydantic v2 CloudEvent did not
override model_validate_json() correctly. Our override now accepts these
newly-added arguments. They have no effect, as the implementation does
not use Pydantic to validate the JSON, but we also don't use field
aliases, so the only effect they could have in the superclass would be
to raise an error if they're both False.

Signed-off-by: Hal Blackburn <hwtb2@cam.ac.uk>

* chore: accept Mapping as well as SupportsDuplicateItems

Although our types.SupportsDuplicateItems type is wider than Dict and
Mapping, it's not a familar type to users, so explicitly accepting
Mapping in the from_http() functions should make it more clear to users
that a dict-like object is required for the headers argument.

Signed-off-by: Hal Blackburn <hwtb2@cam.ac.uk>

* chore: constrain deps to maintain py 3.8 support

Python 3.8 is unsupported and dependencies (such as pydantic) are now
shipping releases that fail to type check with mypy running in 3.8
compatibility mode. We run mypy in py 3.8 compatibility mode, so the
mypy tox environments must only use deps that support 3.8. And unit
tests run by py 3.8 must only use deps that support 3.8.

To constrain the deps for 3.8 support, we use two constraint files, one
for general environments that only constrains the dependencies that
python 3.8 interpreters use, and another for mypy that constraints the
dependencies that all interpreters use.

Signed-off-by: Hal Blackburn <hwtb2@cam.ac.uk>

---------

Signed-off-by: Hal Blackburn <hwtb2@cam.ac.uk>

Author: h4l

.github/workflows/main.yml

@@ -17,7 +17,7 @@ jobs:
       - name: Install dev dependencies
         run: python -m pip install -r requirements/dev.txt
       - name: Run linting
-        run: python -m tox -e lint
+        run: python -m tox -e lint,mypy,mypy-samples-image,mypy-samples-json
 
   test:
     strategy:

cloudevents/abstract/event.py

@@ -32,7 +32,7 @@ class CloudEvent:
     @classmethod
     def create(
         cls: typing.Type[AnyCloudEvent],
-        attributes: typing.Dict[str, typing.Any],
+        attributes: typing.Mapping[str, typing.Any],
         data: typing.Optional[typing.Any],
     ) -> AnyCloudEvent:
         """

cloudevents/conversion.py

@@ -91,7 +91,9 @@ def from_json(
 
 def from_http(
     event_type: typing.Type[AnyCloudEvent],
-    headers: typing.Mapping[str, str],
+    headers: typing.Union[
+        typing.Mapping[str, str], types.SupportsDuplicateItems[str, str]
+    ],
     data: typing.Optional[typing.Union[str, bytes]],
     data_unmarshaller: typing.Optional[types.UnmarshallerType] = None,
 ) -> AnyCloudEvent:
@@ -260,7 +262,7 @@ def best_effort_encode_attribute_value(value: typing.Any) -> typing.Any:
 
 def from_dict(
     event_type: typing.Type[AnyCloudEvent],
-    event: typing.Dict[str, typing.Any],
+    event: typing.Mapping[str, typing.Any],
 ) -> AnyCloudEvent:
     """
     Constructs an Event object of a given `event_type` from

cloudevents/http/conversion.py

@@ -37,7 +37,9 @@ def from_json(
 
 
 def from_http(
-    headers: typing.Dict[str, str],
+    headers: typing.Union[
+        typing.Mapping[str, str], types.SupportsDuplicateItems[str, str]
+    ],
     data: typing.Optional[typing.Union[str, bytes]],
     data_unmarshaller: typing.Optional[types.UnmarshallerType] = None,
 ) -> CloudEvent:
@@ -58,7 +60,7 @@ def from_http(
 
 
 def from_dict(
-    event: typing.Dict[str, typing.Any],
+    event: typing.Mapping[str, typing.Any],
 ) -> CloudEvent:
     """
     Constructs a CloudEvent from a dict `event` representation.

cloudevents/http/event.py

@@ -34,11 +34,13 @@ class CloudEvent(abstract.CloudEvent):
 
     @classmethod
     def create(
-        cls, attributes: typing.Dict[str, typing.Any], data: typing.Optional[typing.Any]
+        cls,
+        attributes: typing.Mapping[str, typing.Any],
+        data: typing.Optional[typing.Any],
     ) -> "CloudEvent":
         return cls(attributes, data)
 
-    def __init__(self, attributes: typing.Dict[str, str], data: typing.Any = None):
+    def __init__(self, attributes: typing.Mapping[str, str], data: typing.Any = None):
         """
         Event Constructor
         :param attributes: a dict with cloudevent attributes. Minimally

cloudevents/kafka/conversion.py

@@ -111,11 +111,29 @@ def to_binary(
     return KafkaMessage(headers, message_key, data)
 
 
+@typing.overload
 def from_binary(
     message: KafkaMessage,
-    event_type: typing.Optional[typing.Type[AnyCloudEvent]] = None,
+    event_type: None = None,
+    data_unmarshaller: typing.Optional[types.UnmarshallerType] = None,
+) -> http.CloudEvent:
+    pass
+
+
+@typing.overload
+def from_binary(
+    message: KafkaMessage,
+    event_type: typing.Type[AnyCloudEvent],
     data_unmarshaller: typing.Optional[types.UnmarshallerType] = None,
 ) -> AnyCloudEvent:
+    pass
+
+
+def from_binary(
+    message: KafkaMessage,
+    event_type: typing.Optional[typing.Type[AnyCloudEvent]] = None,
+    data_unmarshaller: typing.Optional[types.UnmarshallerType] = None,
+) -> typing.Union[http.CloudEvent, AnyCloudEvent]:
     """
     Returns a CloudEvent from a KafkaMessage in binary format.
 
@@ -144,10 +162,11 @@ def from_binary(
         raise cloud_exceptions.DataUnmarshallerError(
             f"Failed to unmarshall data with error: {type(e).__name__}('{e}')"
         )
+    result: typing.Union[http.CloudEvent, AnyCloudEvent]
     if event_type:
         result = event_type.create(attributes, data)
     else:
-        result = http.CloudEvent.create(attributes, data)  # type: ignore
+        result = http.CloudEvent.create(attributes, data)
     return result
 
 
@@ -210,12 +229,32 @@ def to_structured(
     return KafkaMessage(headers, message_key, value)
 
 
+@typing.overload
 def from_structured(
     message: KafkaMessage,
-    event_type: typing.Optional[typing.Type[AnyCloudEvent]] = None,
+    event_type: None = None,
+    data_unmarshaller: typing.Optional[types.UnmarshallerType] = None,
+    envelope_unmarshaller: typing.Optional[types.UnmarshallerType] = None,
+) -> http.CloudEvent:
+    pass
+
+
+@typing.overload
+def from_structured(
+    message: KafkaMessage,
+    event_type: typing.Type[AnyCloudEvent],
     data_unmarshaller: typing.Optional[types.UnmarshallerType] = None,
     envelope_unmarshaller: typing.Optional[types.UnmarshallerType] = None,
 ) -> AnyCloudEvent:
+    pass
+
+
+def from_structured(
+    message: KafkaMessage,
+    event_type: typing.Optional[typing.Type[AnyCloudEvent]] = None,
+    data_unmarshaller: typing.Optional[types.UnmarshallerType] = None,
+    envelope_unmarshaller: typing.Optional[types.UnmarshallerType] = None,
+) -> typing.Union[http.CloudEvent, AnyCloudEvent]:
     """
     Returns a CloudEvent from a KafkaMessage in structured format.
 
@@ -264,8 +303,9 @@ def from_structured(
             attributes["datacontenttype"] = val.decode()
         else:
             attributes[header.lower()] = val.decode()
+    result: typing.Union[AnyCloudEvent, http.CloudEvent]
     if event_type:
         result = event_type.create(attributes, data)
     else:
-        result = http.CloudEvent.create(attributes, data)  # type: ignore
+        result = http.CloudEvent.create(attributes, data)
     return result

cloudevents/pydantic/v1/conversion.py

@@ -21,7 +21,9 @@
 
 
 def from_http(
-    headers: typing.Dict[str, str],
+    headers: typing.Union[
+        typing.Mapping[str, str], types.SupportsDuplicateItems[str, str]
+    ],
     data: typing.Optional[typing.AnyStr],
     data_unmarshaller: typing.Optional[types.UnmarshallerType] = None,
 ) -> CloudEvent:
@@ -63,7 +65,7 @@ def from_json(
 
 
 def from_dict(
-    event: typing.Dict[str, typing.Any],
+    event: typing.Mapping[str, typing.Any],
 ) -> CloudEvent:
     """
     Construct an CloudEvent from a dict `event` representation.

cloudevents/pydantic/v1/event.py

@@ -100,7 +100,9 @@ class CloudEvent(abstract.CloudEvent, BaseModel):  # type: ignore
 
     @classmethod
     def create(
-        cls, attributes: typing.Dict[str, typing.Any], data: typing.Optional[typing.Any]
+        cls,
+        attributes: typing.Mapping[str, typing.Any],
+        data: typing.Optional[typing.Any],
     ) -> "CloudEvent":
         return cls(attributes, data)
 
@@ -155,7 +157,7 @@ def create(
 
     def __init__(  # type: ignore[no-untyped-def]
         self,
-        attributes: typing.Optional[typing.Dict[str, typing.Any]] = None,
+        attributes: typing.Optional[typing.Mapping[str, typing.Any]] = None,
         data: typing.Optional[typing.Any] = None,
         **kwargs,
     ):

cloudevents/pydantic/v2/conversion.py

@@ -22,7 +22,9 @@
 
 
 def from_http(
-    headers: typing.Dict[str, str],
+    headers: typing.Union[
+        typing.Mapping[str, str], types.SupportsDuplicateItems[str, str]
+    ],
     data: typing.Optional[typing.AnyStr],
     data_unmarshaller: typing.Optional[types.UnmarshallerType] = None,
 ) -> CloudEvent:
@@ -64,7 +66,7 @@ def from_json(
 
 
 def from_dict(
-    event: typing.Dict[str, typing.Any],
+    event: typing.Mapping[str, typing.Any],
 ) -> CloudEvent:
     """
     Construct an CloudEvent from a dict `event` representation.

cloudevents/pydantic/v2/event.py

@@ -44,7 +44,9 @@ class CloudEvent(abstract.CloudEvent, BaseModel):  # type: ignore
 
     @classmethod
     def create(
-        cls, attributes: typing.Dict[str, typing.Any], data: typing.Optional[typing.Any]
+        cls,
+        attributes: typing.Mapping[str, typing.Any],
+        data: typing.Optional[typing.Any],
     ) -> "CloudEvent":
         return cls(attributes, data)
 
@@ -103,7 +105,7 @@ def create(
 
     def __init__(  # type: ignore[no-untyped-def]
         self,
-        attributes: typing.Optional[typing.Dict[str, typing.Any]] = None,
+        attributes: typing.Optional[typing.Mapping[str, typing.Any]] = None,
         data: typing.Optional[typing.Any] = None,
         **kwargs,
     ):
@@ -173,6 +175,8 @@ def model_validate_json(
         *,
         strict: typing.Optional[bool] = None,
         context: typing.Optional[typing.Dict[str, Any]] = None,
+        by_alias: typing.Optional[bool] = None,
+        by_name: typing.Optional[bool] = None,
     ) -> "CloudEvent":
         return conversion.from_json(cls, json_data)
 

cloudevents/sdk/event/v1.py

@@ -11,10 +11,15 @@
 #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 #    License for the specific language governing permissions and limitations
 #    under the License.
+from __future__ import annotations
+
 import typing
 
 from cloudevents.sdk.event import base, opt
 
+if typing.TYPE_CHECKING:
+    from typing_extensions import Self
+
 
 class Event(base.BaseEvent):
     _ce_required_fields = {"id", "source", "type", "specversion"}
@@ -79,39 +84,39 @@ def Extensions(self) -> dict:
             return {}
         return dict(result)
 
-    def SetEventType(self, eventType: str) -> base.BaseEvent:
+    def SetEventType(self, eventType: str) -> Self:
         self.Set("type", eventType)
         return self
 
-    def SetSource(self, source: str) -> base.BaseEvent:
+    def SetSource(self, source: str) -> Self:
         self.Set("source", source)
         return self
 
-    def SetEventID(self, eventID: str) -> base.BaseEvent:
+    def SetEventID(self, eventID: str) -> Self:
         self.Set("id", eventID)
         return self
 
-    def SetEventTime(self, eventTime: typing.Optional[str]) -> base.BaseEvent:
+    def SetEventTime(self, eventTime: typing.Optional[str]) -> Self:
         self.Set("time", eventTime)
         return self
 
-    def SetSubject(self, subject: typing.Optional[str]) -> base.BaseEvent:
+    def SetSubject(self, subject: typing.Optional[str]) -> Self:
         self.Set("subject", subject)
         return self
 
-    def SetSchema(self, schema: typing.Optional[str]) -> base.BaseEvent:
+    def SetSchema(self, schema: typing.Optional[str]) -> Self:
         self.Set("dataschema", schema)
         return self
 
-    def SetContentType(self, contentType: typing.Optional[str]) -> base.BaseEvent:
+    def SetContentType(self, contentType: typing.Optional[str]) -> Self:
         self.Set("datacontenttype", contentType)
         return self
 
-    def SetData(self, data: typing.Optional[object]) -> base.BaseEvent:
+    def SetData(self, data: typing.Optional[object]) -> Self:
         self.Set("data", data)
         return self
 
-    def SetExtensions(self, extensions: typing.Optional[dict]) -> base.BaseEvent:
+    def SetExtensions(self, extensions: typing.Optional[dict]) -> Self:
         self.Set("extensions", extensions)
         return self
 

cloudevents/sdk/types.py

@@ -14,9 +14,25 @@
 
 import typing
 
+_K_co = typing.TypeVar("_K_co", covariant=True)
+_V_co = typing.TypeVar("_V_co", covariant=True)
+
 # Use consistent types for marshal and unmarshal functions across
 # both JSON and Binary format.
 
 MarshallerType = typing.Callable[[typing.Any], typing.AnyStr]
 
 UnmarshallerType = typing.Callable[[typing.AnyStr], typing.Any]
+
+
+class SupportsDuplicateItems(typing.Protocol[_K_co, _V_co]):
+    """
+    Dict-like objects with an items() method that may produce duplicate keys.
+    """
+
+    # This is wider than _typeshed.SupportsItems, which expects items() to
+    # return type an AbstractSet. werkzeug's Headers class satisfies this type,
+    # but not _typeshed.SupportsItems.
+
+    def items(self) -> typing.Iterable[typing.Tuple[_K_co, _V_co]]:
+        pass

cloudevents/tests/test_converters.py

@@ -21,7 +21,7 @@
 def test_binary_converter_raise_unsupported():
     with pytest.raises(exceptions.UnsupportedEvent):
         cnvtr = binary.BinaryHTTPCloudEventConverter()
-        cnvtr.read(None, {}, None, None)
+        cnvtr.read(None, {}, None, None)  # type: ignore[arg-type] # intentionally wrong type # noqa: E501
 
 
 def test_base_converters_raise_exceptions():
@@ -35,8 +35,8 @@ def test_base_converters_raise_exceptions():
 
     with pytest.raises(Exception):
         cnvtr = base.Converter()
-        cnvtr.write(None, None)
+        cnvtr.write(None, None)  # type: ignore[arg-type] # intentionally wrong type
 
     with pytest.raises(Exception):
         cnvtr = base.Converter()
-        cnvtr.read(None, None, None, None)
+        cnvtr.read(None, None, None, None)  # type: ignore[arg-type] # intentionally wrong type # noqa: E501

cloudevents/tests/test_event_from_request_converter.py

@@ -25,7 +25,7 @@
 @pytest.mark.parametrize("event_class", [v03.Event, v1.Event])
 def test_binary_converter_upstream(event_class):
     m = marshaller.NewHTTPMarshaller([binary.NewBinaryHTTPCloudEventConverter()])
-    event = m.FromRequest(event_class(), data.headers[event_class], None, lambda x: x)
+    event = m.FromRequest(event_class(), data.headers[event_class], b"", lambda x: x)
     assert event is not None
     assert event.EventType() == data.ce_type
     assert event.EventID() == data.ce_id

cloudevents/tests/test_event_pipeline.py

@@ -77,7 +77,7 @@ def test_object_event_v1():
     _, structured_body = m.ToRequest(event)
     assert isinstance(structured_body, bytes)
     structured_obj = json.loads(structured_body)
-    error_msg = f"Body was {structured_body}, obj is {structured_obj}"
+    error_msg = f"Body was {structured_body!r}, obj is {structured_obj}"
     assert isinstance(structured_obj, dict), error_msg
     assert isinstance(structured_obj["data"], dict), error_msg
     assert len(structured_obj["data"]) == 1, error_msg