fix(data_classes): return None for the SQS attribute value an attribute does not carry

aws_lambda_powertools/utilities/data_classes/sqs_event.py

@@ -74,15 +74,15 @@ class SQSMessageAttribute(DictWrapper):
 
     @property
     def string_value(self) -> str | None:
-        """Strings are Unicode with UTF-8 binary encoding."""
-        return self["stringValue"]
+        """Strings are Unicode with UTF-8 binary encoding. None for a Binary attribute."""
+        return self.get("stringValue")
 
     @property
     def binary_value(self) -> str | None:
         """Binary type attributes can store any binary data, such as compressed data, encrypted data, or images.
 
-        Base64-encoded binary data object"""
-        return self["binaryValue"]
+        Base64-encoded binary data object. None for a String or Number attribute."""
+        return self.get("binaryValue")
 
     @property
     def data_type(self) -> str:

tests/unit/data_classes/required_dependencies/test_sqs_event.py

@@ -169,3 +169,22 @@ def test_sqs_event_typing():
 
     # This assertion compares the return from .items() to the return of __getitem__
     assert list(attributes.items())[0][1] == attributes["key"]
+
+
+def test_sqs_message_attribute_with_only_one_value():
+    # GIVEN message attributes as Lambda delivers them: a String attribute carries no binaryValue
+    # and a Binary attribute carries no stringValue
+    raw_event = load_event("sqsEvent.json")
+    raw_event["Records"][0]["messageAttributes"] = {
+        "text": {"stringValue": "myValue", "stringListValues": [], "binaryListValues": [], "dataType": "String"},
+        "blob": {"binaryValue": "YmFzZTY0", "stringListValues": [], "binaryListValues": [], "dataType": "Binary"},
+    }
+
+    # WHEN reading the attributes
+    attributes = next(SQSEvent(raw_event).records).message_attributes
+
+    # THEN the value a type doesn't carry is None
+    assert attributes["text"].string_value == "myValue"
+    assert attributes["text"].binary_value is None
+    assert attributes["blob"].binary_value == "YmFzZTY0"
+    assert attributes["blob"].string_value is None