feat: Add __str__ to Data Classes base DictWrapper

Add in a __str__ method to the base class used by all Data Classes.
This provides a dictionary string primarily for debugging purposes.

To construct the dictionary a helper method _str_helper recursively
works through `properties` in each instance of a Data Class.

Some Data Classes have sensitive properties, such as credentials,
which can be excluded by setting the `_str_blacklist` attribute
(list of strings).
These properties will have their value replaced with "[SENSITIVE]",
which allows a developer to see a value arrived, but was hidden
as it is sensitive.

Author: neilramsay

aws_lambda_powertools/utilities/data_classes/common.py

@@ -1,7 +1,7 @@
 import base64
 import json
 from collections.abc import Mapping
-from typing import Any, Dict, Iterator, Optional
+from typing import Any, Dict, Iterator, List, Optional
 
 from aws_lambda_powertools.shared.headers_serializer import BaseHeadersSerializer
 
@@ -28,6 +28,49 @@ def __iter__(self) -> Iterator:
     def __len__(self) -> int:
         return len(self._data)
 
+    def __str__(self) -> str:
+        return str(self._str_helper())
+
+    def _str_helper(self) -> Dict[str, Any]:
+        """
+        Recursively get a Dictionary of DictWrapper properties primarily
+        for use by __str__ for debugging purposes.
+
+        Will remove "raw_event" properties, and any defined by the Data Class
+        `_str_sensitive_data` list field.
+        This should be used in case where secrets, such as access keys, are
+        stored in the Data Class but should not be logged out.
+        """
+        properties = self._properties()
+        sensitive_properties = ["raw_event"]
+        try:
+            sensitive_properties.extend(self.__getattribute__("_str_sensitive_data"))
+        except AttributeError:
+            pass
+
+        result: Dict[str, Any] = {}
+        for property_key in properties:
+            if property_key in sensitive_properties:
+                result[property_key] = "[SENSITIVE]"
+            else:
+                try:
+                    property_value = getattr(self, property_key)
+                    result[property_key] = property_value
+
+                    if issubclass(property_value.__class__, DictWrapper):
+                        result[property_key] = property_value._str_helper()
+                    elif isinstance(property_value, list):
+                        for seq, item in enumerate(property_value):
+                            if issubclass(item.__class__, DictWrapper):
+                                result[property_key][seq] = item._str_helper()
+                except Exception as e:
+                    result[property_key] = f"[EXCEPTION {type(e)}]"
+
+        return result
+
+    def _properties(self) -> List[str]:
+        return [p for p in dir(self.__class__) if isinstance(getattr(self.__class__, p), property)]
+
     def get(self, key: str, default: Optional[Any] = None) -> Optional[Any]:
         return self._data.get(key, default)