fix: Fix issue with strip_prefixes (#647)

* Fix issue with strip_prefixes

* Add test

* Update docs to clarify usage

Co-authored-by: Brian Villemarette <[email protected]>

Author: BVMiko

Diff for: aws_lambda_powertools/event_handler/api_gateway.py

@@ -546,6 +546,8 @@ def _remove_prefix(self, path: str) -> str:
             return path
 
         for prefix in self._strip_prefixes:
+            if path == prefix:
+                return "/"
             if self._path_starts_with(path, prefix):
                 return path[len(prefix) :]
 

Diff for: docs/core/event_handler/api_gateway.md

@@ -476,6 +476,8 @@ This will lead to a HTTP 404 despite having your Lambda configured correctly. Se
     }
     ```
 
+Note: After removing a path prefix with `strip_prefixes`, the new root path will automatically be mapped to the path argument of `/`. For example, when using `strip_prefixes` value of `/pay`, there is no difference between a request path of `/pay` and `/pay/`; and the path argument would be defined as `/`.
+
 ## Advanced
 
 ### CORS

Diff for: tests/functional/event_handler/test_api_gateway.py

@@ -842,3 +842,21 @@ def foo():
     # THEN process event correctly
     assert result["statusCode"] == 200
     assert result["headers"]["Content-Type"] == content_types.APPLICATION_JSON
+
+
+def test_api_gateway_request_path_equals_strip_prefix():
+    # GIVEN a strip_prefix matches the request path
+    app = ApiGatewayResolver(strip_prefixes=["/foo"])
+    event = {"httpMethod": "GET", "path": "/foo"}
+
+    @app.get("/")
+    def base():
+        return {}
+
+    # WHEN calling the event handler
+    # WITH a route "/"
+    result = app(event, {})
+
+    # THEN process event correctly
+    assert result["statusCode"] == 200
+    assert result["headers"]["Content-Type"] == content_types.APPLICATION_JSON