feat(event_source): support custom json_deserializer; add json_body in SQSEvent

aws_lambda_powertools/utilities/data_classes/common.py

@@ -1,17 +1,27 @@
 import base64
 import json
 from collections.abc import Mapping
-from typing import Any, Dict, Iterator, List, Optional
+from typing import Any, Callable, Dict, Iterator, List, Optional
 
 from aws_lambda_powertools.shared.headers_serializer import BaseHeadersSerializer
 
 
 class DictWrapper(Mapping):
     """Provides a single read only access to a wrapper dict"""
 
-    def __init__(self, data: Dict[str, Any]):
+    def __init__(self, data: Dict[str, Any], json_deserializer: Optional[Callable] = None):
+        """
+        Parameters
+        ----------
+        data : Dict[str, Any]
+            Lambda Event Source Event payload
+        json_deserializer : Callable, optional
+            function to deserialize `str`, `bytes`, bytearray` containing a JSON document to a Python `obj`,
+            by default json.loads
+        """
         self._data = data
         self._json_data: Optional[Any] = None
+        self._json_deserializer = json_deserializer or json.loads
 
     def __getitem__(self, key: str) -> Any:
         return self._data[key]
@@ -122,7 +132,7 @@ def body(self) -> Optional[str]:
     def json_body(self) -> Any:
         """Parses the submitted body as json"""
         if self._json_data is None:
-            self._json_data = json.loads(self.decoded_body)
+            self._json_data = self._json_deserializer(self.decoded_body)
         return self._json_data
 
     @property

aws_lambda_powertools/utilities/data_classes/kafka_event.py

@@ -1,5 +1,4 @@
 import base64
-import json
 from typing import Any, Dict, Iterator, List, Optional
 
 from aws_lambda_powertools.utilities.data_classes.common import DictWrapper
@@ -55,7 +54,7 @@ def decoded_value(self) -> bytes:
     def json_value(self) -> Any:
         """Decodes the text encoded data as JSON."""
         if self._json_data is None:
-            self._json_data = json.loads(self.decoded_value.decode("utf-8"))
+            self._json_data = self._json_deserializer(self.decoded_value.decode("utf-8"))
         return self._json_data
 
     @property
@@ -117,7 +116,7 @@ def records(self) -> Iterator[KafkaEventRecord]:
         """The Kafka records."""
         for chunk in self["records"].values():
             for record in chunk:
-                yield KafkaEventRecord(record)
+                yield KafkaEventRecord(data=record, json_deserializer=self._json_deserializer)
 
     @property
     def record(self) -> KafkaEventRecord:

aws_lambda_powertools/utilities/data_classes/kinesis_firehose_event.py

@@ -1,5 +1,4 @@
 import base64
-import json
 from typing import Iterator, Optional
 
 from aws_lambda_powertools.utilities.data_classes.common import DictWrapper
@@ -75,7 +74,7 @@ def data_as_text(self) -> str:
     def data_as_json(self) -> dict:
         """Decoded base64-encoded data loaded to json"""
         if self._json_data is None:
-            self._json_data = json.loads(self.data_as_text)
+            self._json_data = self._json_deserializer(self.data_as_text)
         return self._json_data
 
 
@@ -110,4 +109,4 @@ def region(self) -> str:
     @property
     def records(self) -> Iterator[KinesisFirehoseRecord]:
         for record in self["records"]:
-            yield KinesisFirehoseRecord(record)
+            yield KinesisFirehoseRecord(data=record, json_deserializer=self._json_deserializer)

aws_lambda_powertools/utilities/data_classes/sqs_event.py

@@ -1,4 +1,4 @@
-from typing import Dict, Iterator, Optional
+from typing import Any, Dict, Iterator, Optional
 
 from aws_lambda_powertools.utilities.data_classes.common import DictWrapper
 
@@ -103,6 +103,35 @@ def body(self) -> str:
         """The message's contents (not URL-encoded)."""
         return self["body"]
 
+    @property
+    def json_body(self) -> Any:
+        """Deserializes JSON string available in 'body' property
+
+        Notes
+        -----
+
+        **Strict typing**
+
+        Caller controls the type as we can't use recursive generics here.
+
+        JSON Union types would force caller to have to cast a type. Instead,
+        we choose Any to ease ergonomics and other tools receiving this data.
+
+        Examples
+        --------
+
+        **Type deserialized data from JSON string**
+
+        ```python
+        data: dict = record.json_body  # {"telemetry": [], ...}
+        # or
+        data: list = record.json_body  # ["telemetry_values"]
+        ```
+        """
+        if self._json_data is None:
+            self._json_data = self._json_deserializer(self["body"])
+        return self._json_data
+
     @property
     def attributes(self) -> SQSRecordAttributes:
         """A map of the attributes requested in ReceiveMessage to their respective values."""
@@ -157,4 +186,4 @@ class SQSEvent(DictWrapper):
     @property
     def records(self) -> Iterator[SQSRecord]:
         for record in self["Records"]:
-            yield SQSRecord(record)
+            yield SQSRecord(data=record, json_deserializer=self._json_deserializer)

tests/events/sqsEvent.json

@@ -25,7 +25,7 @@
     {
       "messageId": "2e1424d4-f796-459a-8184-9c92662be6da",
       "receiptHandle": "AQEBzWwaftRI0KuVm4tP+/7q1rGgNqicHq...",
-      "body": "Test message2.",
+      "body": "{\"message\": \"foo1\"}",
       "attributes": {
         "ApproximateReceiveCount": "1",
         "SentTimestamp": "1545082650636",
@@ -39,4 +39,4 @@
       "awsRegion": "us-east-2"
     }
   ]
-}
+}

tests/functional/test_data_classes.py

@@ -113,6 +113,47 @@ def message(self) -> str:
     assert DataClassSample(data1).raw_event is data1
 
 
+def test_dict_wrapper_with_default_custom_json_deserializer():
+    class DataClassSample(DictWrapper):
+        @property
+        def json_body(self) -> dict:
+            return self._json_deserializer(self["body"])
+
+    data = {"body": '{"message": "foo1"}'}
+    event = DataClassSample(data=data)
+    assert event.json_body == json.loads(data["body"])
+
+
+def test_dict_wrapper_with_valid_custom_json_deserializer():
+    class DataClassSample(DictWrapper):
+        @property
+        def json_body(self) -> dict:
+            return self._json_deserializer(self["body"])
+
+    def fake_json_deserializer(record: dict):
+        return json.loads(record)
+
+    data = {"body": '{"message": "foo1"}'}
+    event = DataClassSample(data=data, json_deserializer=fake_json_deserializer)
+    assert event.json_body == json.loads(data["body"])
+
+
+def test_dict_wrapper_with_invalid_custom_json_deserializer():
+    class DataClassSample(DictWrapper):
+        @property
+        def json_body(self) -> dict:
+            return self._json_deserializer(self["body"])
+
+    def fake_json_deserializer() -> None:
+        # invalid fn signature should raise TypeError
+        pass
+
+    data = {"body": {"message": "foo1"}}
+    with pytest.raises(TypeError):
+        event = DataClassSample(data=data, json_deserializer=fake_json_deserializer)
+        assert event.json_body == {"message": "foo1"}
+
+
 def test_dict_wrapper_implements_mapping():
     class DataClassSample(DictWrapper):
         pass
@@ -926,6 +967,9 @@ def test_seq_trigger_event():
     assert record.queue_url == "https://sqs.us-east-2.amazonaws.com/123456789012/my-queue"
     assert record.aws_region == "us-east-2"
 
+    record_2 = records[1]
+    assert record_2.json_body == {"message": "foo1"}
+
 
 def test_default_api_gateway_proxy_event():
     event = APIGatewayProxyEvent(load_event("apiGatewayProxyEvent_noVersionAuth.json"))