#7123 Tech debt: Improve documentation of Event model fields in DynamoDB parser models

Author: sreejaaryahi18

aws_lambda_powertools/utilities/parser/models/dynamodb.py

@@ -2,53 +2,133 @@
 from datetime import datetime
 from typing import Any, Dict, List, Literal, Optional, Type, Union
 
-from pydantic import BaseModel, field_validator
-
+from pydantic import BaseModel, Field, field_validator
 from aws_lambda_powertools.shared.dynamodb_deserializer import TypeDeserializer
 
 _DESERIALIZER = TypeDeserializer()
 
 
 class DynamoDBStreamChangedRecordModel(BaseModel):
-    ApproximateCreationDateTime: Optional[datetime] = None
-    Keys: Dict[str, Any]
-    NewImage: Optional[Union[Dict[str, Any], Type[BaseModel], BaseModel]] = None
-    OldImage: Optional[Union[Dict[str, Any], Type[BaseModel], BaseModel]] = None
-    SequenceNumber: str
-    SizeBytes: int
-    StreamViewType: Literal["NEW_AND_OLD_IMAGES", "KEYS_ONLY", "NEW_IMAGE", "OLD_IMAGE"]
-
-    # context on why it's commented: https://github.com/aws-powertools/powertools-lambda-python/pull/118
-    # since both images are optional, they can both be None. However, at least one must
-    # exist in a legal model of NEW_AND_OLD_IMAGES type
-    # @root_validator
-    # def check_one_image_exists(cls, values): # noqa: ERA001
-    #     new_img, old_img = values.get("NewImage"), values.get("OldImage") # noqa: ERA001
-    #     stream_type = values.get("StreamViewType") # noqa: ERA001
-    #     if stream_type == "NEW_AND_OLD_IMAGES" and not new_img and not old_img: # noqa: ERA001
-    #         raise TypeError("DynamoDB streams model failed validation, missing both new & old stream images") # noqa: ERA001,E501
-    #     return values # noqa: ERA001
+    ApproximateCreationDateTime: Optional[float] = Field(  # AWS sends this as Unix epoch float
+        default=None,
+        description="The approximate date and time when the stream record was created (Unix epoch time).",
+        examples=[1693997155.0]
+    )
+    Keys: Dict[str, Any] = Field(
+        description="Primary key attributes for the item.",
+        examples=[{"Id": {"N": "101"}}]
+    )
+    NewImage: Optional[Union[Dict[str, Any], Type[BaseModel], BaseModel]] = Field(
+        default=None,
+        description="The item after modifications, in DynamoDB attribute-value format.",
+        examples=[{
+            "Message": {"S": "New item!"},
+            "Id": {"N": "101"}
+        }]
+    )
+    OldImage: Optional[Union[Dict[str, Any], Type[BaseModel], BaseModel]] = Field(
+        default=None,
+        description="The item before modifications, in DynamoDB attribute-value format.",
+        examples=[{
+            "Message": {"S": "Old item!"},
+            "Id": {"N": "100"}
+        }]
+    )
+    SequenceNumber: str = Field(
+        description="A unique identifier for the stream record.",
+        examples=["222"]
+    )
+    SizeBytes: int = Field(
+        description="The size of the stream record, in bytes.",
+        examples=[26]
+    )
+    StreamViewType: Literal["NEW_AND_OLD_IMAGES", "KEYS_ONLY", "NEW_IMAGE", "OLD_IMAGE"] = Field(
+        description="The type of data included in the stream record.",
+        examples=["NEW_AND_OLD_IMAGES"]
+    )
 
     @field_validator("Keys", "NewImage", "OldImage", mode="before")
     def deserialize_field(cls, value):
-        return {k: _DESERIALIZER.deserialize(v) for k, v in value.items()}
+        return {k: _DESERIALIZER.deserialize(v) for k, v in value.items()} if value else value
 
 
 class UserIdentity(BaseModel):
-    type: Literal["Service"]  # noqa: VNE003, A003
-    principalId: Literal["dynamodb.amazonaws.com"]
+    type: Literal["Service"] = Field(
+        default="Service",
+        description="The type of identity that made the request, which is always 'Service' for DynamoDB streams.",
+        examples=["Service"]
+    )
+    principalId: str = Field(
+        description="The unique identifier for the principal that made the request.",
+        examples=["dynamodb.amazonaws.com"]
+    )
 
 
 class DynamoDBStreamRecordModel(BaseModel):
-    eventID: str
-    eventName: Literal["INSERT", "MODIFY", "REMOVE"]
-    eventVersion: float
-    eventSource: Literal["aws:dynamodb"]
-    awsRegion: str
-    eventSourceARN: str
-    dynamodb: DynamoDBStreamChangedRecordModel
-    userIdentity: Optional[UserIdentity] = None
+    eventID: str = Field(
+        description="A unique identifier for the event.",
+        examples=["1"]
+    )
+    eventName: Literal["INSERT", "MODIFY", "REMOVE"] = Field(
+        description="The type of operation that was performed on the item.",
+        examples=["INSERT"]
+    )
+    eventVersion: str = Field(
+        default="1.0",
+        description="The version of the stream record format.",
+        examples=["1.0"]
+    )
+    eventSource: str = Field(
+        default="aws:dynamodb",
+        description="The source of the event, which is always 'aws:dynamodb' for DynamoDB streams.",
+        examples=["aws:dynamodb"]
+    )
+    awsRegion: str = Field(
+        description="The AWS region where the stream record was generated.",
+        examples=["us-west-2"]
+    )
+    eventSourceARN: str = Field(
+        description="The Amazon Resource Name (ARN) of the DynamoDB stream.",
+        examples=["arn:aws:dynamodb:us-west-2:123456789012:table/ExampleTable/stream/2021-01-01T00:00:00.000"]
+    )
+    dynamodb: DynamoDBStreamChangedRecordModel = Field(
+        description="Contains the details of the DynamoDB stream record.",
+        examples=[{
+            "ApproximateCreationDateTime": 1693997155.0,
+            "Keys": {"Id": {"N": "101"}},
+            "NewImage": {"Message": {"S": "New item!"}, "Id": {"N": "101"}},
+            "OldImage": {"Message": {"S": "Old item!"}, "Id": {"N": "100"}},
+            "SequenceNumber": "222",
+            "SizeBytes": 26,
+            "StreamViewType": "NEW_AND_OLD_IMAGES"
+        }]
+    )
+    userIdentity: Optional[UserIdentity] = Field(
+        default=None,
+        description="Information about the identity that made the request.",
+        examples=[{"type": "Service", "principalId": "dynamodb.amazonaws.com"}]
+    )
 
 
 class DynamoDBStreamModel(BaseModel):
-    Records: List[DynamoDBStreamRecordModel]
+    Records: List[DynamoDBStreamRecordModel] = Field(
+        description="A list of records that contain the details of the DynamoDB stream events.",
+        examples=[{
+            "eventID": "1",
+            "eventName": "INSERT",
+            "eventVersion": "1.0",
+            "eventSource": "aws:dynamodb",
+            "awsRegion": "us-west-2",
+            "eventSourceARN": "arn:aws:dynamodb:us-west-2:123456789012:table/ExampleTable/stream/2021-01-01T00:00:00.000",
+            "dynamodb": {
+                "ApproximateCreationDateTime": 1693997155.0,
+                "Keys": {"Id": {"N": "101"}},
+                "NewImage": {"Message": {"S": "New item!"}, "Id": {"N": "101"}},
+                "OldImage": {"Message": {"S": "Old item!"}, "Id": {"N": "100"}},
+                "SequenceNumber": "222",
+                "SizeBytes": 26,
+                "StreamViewType": "NEW_AND_OLD_IMAGES"
+            },
+            "userIdentity": {"type": "Service", "principalId": "dynamodb.amazonaws.com"}
+        }]
+    )