chore: Add copyright and fix missing type info

Signed-off-by: Tudor Plugaru <plugaru.tudor@protonmail.com>

Author: PlugaruT

src/cloudevents/core/v1/__init__.py

@@ -1,3 +1,17 @@
+#  Copyright 2018-Present The CloudEvents Authors
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
 """
 CloudEvent implementation for v1.0
 """

src/cloudevents/core/v1/event.py

@@ -12,34 +12,48 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-from typing import Any, Optional
+from typing import Any, Optional, Final
 from datetime import datetime
 import re
 
-REQUIRED_ATTRIBUTES = {"id", "source", "type", "specversion"}
-OPTIONAL_ATTRIBUTES = {"datacontenttype", "dataschema", "subject", "time"}
+REQUIRED_ATTRIBUTES: Final[set[str]] = {"id", "source", "type", "specversion"}
+OPTIONAL_ATTRIBUTES: Final[set[str]] = {
+    "datacontenttype",
+    "dataschema",
+    "subject",
+    "time",
+}
 
 
 class CloudEvent:
-    def __init__(self, attributes: dict, data: Optional[dict] = None) -> None:
+    """
+    The CloudEvent Python wrapper contract exposing generically-available
+    properties and APIs.
+
+    Implementations might handle fields and have other APIs exposed but are
+    obliged to follow this contract.
+    """
+
+    def __init__(self, attributes: dict[str, Any], data: Optional[dict] = None) -> None:
         """
         Create a new CloudEvent instance.
 
         :param attributes: The attributes of the CloudEvent instance.
-        :type attributes: dict
         :param data: The payload of the CloudEvent instance.
-        :type data: Optional[dict]
 
         :raises ValueError: If any of the required attributes are missing or have invalid values.
         :raises TypeError: If any of the attributes have invalid types.
         """
         self._validate_attribute(attributes)
-        self._attributes = attributes
-        self._data = data
+        self._attributes: dict = attributes
+        self._data: Optional[dict] = data
 
-    def _validate_attribute(self, attributes: dict) -> None:
+    @staticmethod
+    def _validate_attribute(attributes: dict) -> None:
         """
-        Private method that validates the attributes of the CloudEvent as per the CloudEvents specification.
+        Validates the attributes of the CloudEvent as per the CloudEvents specification.
+
+        See https://github.com/cloudevents/spec/blob/main/cloudevents/spec.md#required-attributes
         """
         missing_attributes = [
             attr for attr in REQUIRED_ATTRIBUTES if attr not in attributes
@@ -95,38 +109,31 @@ def _validate_attribute(self, attributes: dict) -> None:
             if not attributes["dataschema"]:
                 raise ValueError("Attribute 'dataschema' must not be empty")
 
-        for custom_extension in (
+        for extension_attributes in (
             set(attributes.keys()) - REQUIRED_ATTRIBUTES - OPTIONAL_ATTRIBUTES
         ):
-            if custom_extension == "data":
+            if extension_attributes == "data":
                 raise ValueError(
                     "Extension attribute 'data' is reserved and must not be used"
                 )
 
-            if not custom_extension[0].isalpha():
-                raise ValueError(
-                    f"Extension attribute '{custom_extension}' should start with a letter"
-                )
-
-            if not (5 <= len(custom_extension) <= 20):
+            if not (1 <= len(extension_attributes) <= 20):
                 raise ValueError(
-                    f"Extension attribute '{custom_extension}' should be between 5 and 20 characters long"
+                    f"Extension attribute '{extension_attributes}' should be between 1 and 20 characters long"
                 )
 
-            if not re.match(r"^[a-z0-9]+$", custom_extension):
+            if not re.match(r"^[a-z0-9]+$", extension_attributes):
                 raise ValueError(
-                    f"Extension attribute '{custom_extension}' should only contain lowercase letters and numbers"
+                    f"Extension attribute '{extension_attributes}' should only contain lowercase letters and numbers"
                 )
 
     def get_attribute(self, attribute: str) -> Optional[Any]:
         """
         Retrieve a value of an attribute of the event denoted by the given `attribute`.
 
         :param attribute: The name of the event attribute to retrieve the value for.
-        :type attribute: str
 
         :return: The event attribute value.
-        :rtype: Optional[Any]
         """
         return self._attributes[attribute]
 
@@ -135,6 +142,5 @@ def get_data(self) -> Optional[dict]:
         Retrieve data of the event.
 
         :return: The data of the event.
-        :rtype: Optional[dict]
         """
         return self._data

tests/test_core/__init__.py

@@ -0,0 +1,13 @@
+#  Copyright 2018-Present The CloudEvents Authors
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.

tests/test_core/test_v1/__init__.py

@@ -0,0 +1,13 @@
+#  Copyright 2018-Present The CloudEvents Authors
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.

tests/test_core/test_v1/test_event.py

@@ -1,3 +1,17 @@
+#  Copyright 2018-Present The CloudEvents Authors
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    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 cloudevents.core.v1.event import CloudEvent
 
 import pytest
@@ -162,14 +176,13 @@ def test_dataschema_validation(dataschema: Any, error: str) -> None:
 @pytest.mark.parametrize(
     "extension_name,error",
     [
-        ("123", "Extension attribute '123' should start with a letter"),
         (
-            "shrt",
-            "Extension attribute 'shrt' should be between 5 and 20 characters long",
+            "",
+            "Extension attribute '' should be between 1 and 20 characters long",
         ),
         (
             "thisisaverylongextension",
-            "Extension attribute 'thisisaverylongextension' should be between 5 and 20 characters long",
+            "Extension attribute 'thisisaverylongextension' should be between 1 and 20 characters long",
         ),
         (
             "ThisIsNotValid",