fix(typing): improve overloads to ensure the return type follows the default_value type (aws-powertools#4114)

Author: tonnico

aws_lambda_powertools/utilities/data_classes/api_gateway_authorizer_event.py

@@ -283,6 +283,17 @@ def path_parameters(self) -> Optional[Dict[str, str]]:
     def stage_variables(self) -> Optional[Dict[str, str]]:
         return self.get("stageVariables")
 
+    @overload
+    def get_header_value(self, name: str, default_value: str, case_sensitive: bool = False) -> str: ...
+
+    @overload
+    def get_header_value(
+        self,
+        name: str,
+        default_value: Optional[str] = None,
+        case_sensitive: Optional[bool] = False,
+    ) -> Optional[str]: ...
+
     def get_header_value(
         self,
         name: str,

aws_lambda_powertools/utilities/data_classes/appsync_resolver_event.py

@@ -1,4 +1,4 @@
-from typing import Any, Dict, List, Optional, Union
+from typing import Any, Dict, List, Optional, Union, overload
 
 from aws_lambda_powertools.utilities.data_classes.common import DictWrapper
 from aws_lambda_powertools.utilities.data_classes.shared_functions import (
@@ -214,6 +214,22 @@ def stash(self) -> Optional[dict]:
         a pipeline resolver."""
         return self.get("stash")
 
+    @overload
+    def get_header_value(
+        self,
+        name: str,
+        default_value: str,
+        case_sensitive: Optional[bool] = False,
+    ) -> str: ...
+
+    @overload
+    def get_header_value(
+        self,
+        name: str,
+        default_value: Optional[str] = None,
+        case_sensitive: Optional[bool] = False,
+    ) -> Optional[str]: ...
+
     def get_header_value(
         self,
         name: str,

aws_lambda_powertools/utilities/data_classes/common.py

@@ -172,6 +172,12 @@ def http_method(self) -> str:
         """The HTTP method used. Valid values include: DELETE, GET, HEAD, OPTIONS, PATCH, POST, and PUT."""
         return self["httpMethod"]
 
+    @overload
+    def get_query_string_value(self, name: str, default_value: str) -> str: ...
+
+    @overload
+    def get_query_string_value(self, name: str, default_value: Optional[str] = None) -> Optional[str]: ...
+
     def get_query_string_value(self, name: str, default_value: Optional[str] = None) -> Optional[str]:
         """Get query string value by name
 

aws_lambda_powertools/utilities/data_classes/kafka_event.py

@@ -1,6 +1,6 @@
 import base64
 from functools import cached_property
-from typing import Any, Dict, Iterator, List, Optional
+from typing import Any, Dict, Iterator, List, Optional, overload
 
 from aws_lambda_powertools.utilities.data_classes.common import DictWrapper
 from aws_lambda_powertools.utilities.data_classes.shared_functions import (
@@ -69,10 +69,26 @@ def decoded_headers(self) -> Dict[str, bytes]:
         """Decodes the headers as a single dictionary."""
         return {k: bytes(v) for chunk in self.headers for k, v in chunk.items()}
 
+    @overload
     def get_header_value(
         self,
         name: str,
-        default_value: Optional[Any] = None,
+        default_value: str,
+        case_sensitive: bool = True,
+    ) -> str: ...
+
+    @overload
+    def get_header_value(
+        self,
+        name: str,
+        default_value: Optional[str] = None,
+        case_sensitive: bool = True,
+    ) -> Optional[str]: ...
+
+    def get_header_value(
+        self,
+        name: str,
+        default_value: Optional[str] = None,
         case_sensitive: bool = True,
     ) -> Optional[str]:
         """Get a decoded header value by name."""

aws_lambda_powertools/utilities/data_classes/s3_object_event.py

@@ -1,4 +1,4 @@
-from typing import Dict, Optional
+from typing import Dict, Optional, overload
 
 from aws_lambda_powertools.utilities.data_classes.common import DictWrapper
 from aws_lambda_powertools.utilities.data_classes.shared_functions import (
@@ -73,6 +73,22 @@ def headers(self) -> Dict[str, str]:
         The case of the original headers is retained in this map."""
         return self["headers"]
 
+    @overload
+    def get_header_value(
+        self,
+        name: str,
+        default_value: str,
+        case_sensitive: Optional[bool] = False,
+    ) -> str: ...
+
+    @overload
+    def get_header_value(
+        self,
+        name: str,
+        default_value: Optional[str] = None,
+        case_sensitive: Optional[bool] = False,
+    ) -> Optional[str]: ...
+
     def get_header_value(
         self,
         name: str,

aws_lambda_powertools/utilities/data_classes/shared_functions.py

@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 import base64
-from typing import Any, Dict
+from typing import Any, Dict, overload
 
 
 def base64_decode(value: str) -> str:
@@ -21,11 +21,29 @@ def base64_decode(value: str) -> str:
     return base64.b64decode(value).decode("UTF-8")
 
 
+@overload
 def get_header_value(
     headers: dict[str, Any],
     name: str,
-    default_value: str | None,
-    case_sensitive: bool | None,
+    default_value: str,
+    case_sensitive: bool | None = False,
+) -> str: ...
+
+
+@overload
+def get_header_value(
+    headers: dict[str, Any],
+    name: str,
+    default_value: str | None = None,
+    case_sensitive: bool | None = False,
+) -> str | None: ...
+
+
+def get_header_value(
+    headers: dict[str, Any],
+    name: str,
+    default_value: str | None = None,
+    case_sensitive: bool | None = False,
 ) -> str | None:
     """
     Get the value of a header by its name.
@@ -39,7 +57,7 @@ def get_header_value(
     default_value: str, optional
         The default value to return if the header is not found. Default is None.
     case_sensitive: bool, optional
-        Indicates whether the header name should be case-sensitive. Default is None.
+        Indicates whether the header name should be case-sensitive. Default is False.
 
     Returns
     -------
@@ -62,6 +80,22 @@ def get_header_value(
     )
 
 
+@overload
+def get_query_string_value(
+    query_string_parameters: Dict[str, str] | None,
+    name: str,
+    default_value: str,
+) -> str: ...
+
+
+@overload
+def get_query_string_value(
+    query_string_parameters: Dict[str, str] | None,
+    name: str,
+    default_value: str | None = None,
+) -> str | None: ...
+
+
 def get_query_string_value(
     query_string_parameters: Dict[str, str] | None,
     name: str,

aws_lambda_powertools/utilities/data_classes/vpc_lattice.py

@@ -47,6 +47,12 @@ def http_method(self) -> str:
         """The HTTP method used. Valid values include: DELETE, GET, HEAD, OPTIONS, PATCH, POST, and PUT."""
         return self["method"]
 
+    @overload
+    def get_query_string_value(self, name: str, default_value: str) -> str: ...
+
+    @overload
+    def get_query_string_value(self, name: str, default_value: Optional[str] = None) -> Optional[str]: ...
+
     def get_query_string_value(self, name: str, default_value: Optional[str] = None) -> Optional[str]:
         """Get query string value by name
 

examples/event_handler_graphql/src/custom_models.py

@@ -26,11 +26,11 @@ class Location(TypedDict, total=False):
 class MyCustomModel(AppSyncResolverEvent):
     @property
     def country_viewer(self) -> str:
-        return self.get_header_value(name="cloudfront-viewer-country", default_value="", case_sensitive=False)  # type: ignore[return-value] # sentinel typing # noqa: E501
+        return self.get_header_value(name="cloudfront-viewer-country", default_value="", case_sensitive=False)
 
     @property
     def api_key(self) -> str:
-        return self.get_header_value(name="x-api-key", default_value="", case_sensitive=False)  # type: ignore[return-value] # sentinel typing # noqa: E501
+        return self.get_header_value(name="x-api-key", default_value="", case_sensitive=False)
 
 
 @app.resolver(type_name="Query", field_name="listLocations")