feat(event-sources): cache parsed json in data class

aws_lambda_powertools/utilities/data_classes/common.py

@@ -45,6 +45,10 @@ def get_header_value(
 
 
 class BaseProxyEvent(DictWrapper):
+    def __init__(self, data: Dict[str, Any]):
+        super().__init__(data)
+        self._parsed_json_body: Optional[Any] = None
+
     @property
     def headers(self) -> Dict[str, str]:
         return self["headers"]
@@ -65,7 +69,11 @@ def body(self) -> Optional[str]:
     @property
     def json_body(self) -> Any:
         """Parses the submitted body as json"""
-        return json.loads(self.decoded_body)
+        if self._parsed_json_body:
+            return self._parsed_json_body
+
+        self._parsed_json_body = json.loads(self.decoded_body)
+        return self._parsed_json_body
 
     @property
     def decoded_body(self) -> str:

tests/functional/test_data_classes.py

@@ -1053,7 +1053,9 @@ def test_base_proxy_event_json_body_key_error():
 def test_base_proxy_event_json_body():
     data = {"message": "Foo"}
     event = BaseProxyEvent({"body": json.dumps(data)})
+    assert event._parsed_json_body is None
     assert event.json_body == data
+    assert event.json_body == event._parsed_json_body == data
 
 
 def test_base_proxy_event_decode_body_key_error():
@@ -1084,7 +1086,7 @@ def test_base_proxy_event_json_body_with_base64_encoded_data():
     event = BaseProxyEvent({"body": encoded_data, "isBase64Encoded": True})
 
     # WHEN calling json_body
-    # THEN then base64 decode and json load
+    # THEN base64 decode and json load
     assert event.json_body == data