feat(apigateway): ignore trailing slashes in routes (APIGatewayRestResolver) (#1609)

Co-authored-by: Heitor Lessa <[email protected]>

Author: walmsles

aws_lambda_powertools/event_handler/api_gateway.py

@@ -46,6 +46,7 @@
 # API GW/ALB decode non-safe URI chars; we must support them too
 _UNSAFE_URI = "%<> \[\]{}|^"  # noqa: W605
 _NAMED_GROUP_BOUNDARY_PATTERN = rf"(?P\1[{_SAFE_URI}{_UNSAFE_URI}\\w]+)"
+_ROUTE_REGEX = "^{}$"
 
 
 class ProxyEventType(Enum):
@@ -562,7 +563,7 @@ def _has_debug(debug: Optional[bool] = None) -> bool:
         return powertools_dev_is_set()
 
     @staticmethod
-    def _compile_regex(rule: str):
+    def _compile_regex(rule: str, base_regex: str = _ROUTE_REGEX):
         """Precompile regex pattern
 
         Logic
@@ -592,7 +593,7 @@ def _compile_regex(rule: str):
         NOTE: See #520 for context
         """
         rule_regex: str = re.sub(_DYNAMIC_ROUTE_PATTERN, _NAMED_GROUP_BOUNDARY_PATTERN, rule)
-        return re.compile("^{}$".format(rule_regex))
+        return re.compile(base_regex.format(rule_regex))
 
     def _to_proxy_event(self, event: Dict) -> BaseProxyEvent:
         """Convert the event dict to the corresponding data class"""
@@ -819,6 +820,24 @@ def __init__(
         """Amazon API Gateway REST and HTTP API v1 payload resolver"""
         super().__init__(ProxyEventType.APIGatewayProxyEvent, cors, debug, serializer, strip_prefixes)
 
+    # override route to ignore trailing "/" in routes for REST API
+    def route(
+        self,
+        rule: str,
+        method: Union[str, Union[List[str], Tuple[str]]],
+        cors: Optional[bool] = None,
+        compress: bool = False,
+        cache_control: Optional[str] = None,
+    ):
+        # NOTE: see #1552 for more context.
+        return super().route(rule.rstrip("/"), method, cors, compress, cache_control)
+
+    # Override _compile_regex to exclude trailing slashes for route resolution
+    @staticmethod
+    def _compile_regex(rule: str, base_regex: str = _ROUTE_REGEX):
+
+        return super(APIGatewayRestResolver, APIGatewayRestResolver)._compile_regex(rule, "^{}/*$")
+
 
 class APIGatewayHttpResolver(ApiGatewayResolver):
     current_event: APIGatewayProxyEventV2

docs/core/event_handler/api_gateway.md

@@ -42,19 +42,19 @@ Before you decorate your functions to handle a given path and HTTP method(s), yo
 
 A resolver will handle request resolution, including [one or more routers](#split-routes-with-router), and give you access to the current event via typed properties.
 
-For resolvers, we provide: `APIGatewayRestResolver`, `APIGatewayHttpResolver`, `ALBResolver`, and `LambdaFunctionUrlResolver` .
+For resolvers, we provide: `APIGatewayRestResolver`, `APIGatewayHttpResolver`, `ALBResolver`, and `LambdaFunctionUrlResolver`. From here on, we will default to `APIGatewayRestResolver` across examples.
 
-???+ info
-    We will use `APIGatewayRestResolver` as the default across examples.
+???+ info "Auto-serialization"
+    We serialize `Dict` responses as JSON, trim whitespace for compact responses, and set content-type to `application/json`.
 
 #### API Gateway REST API
 
 When using Amazon API Gateway REST API to front your Lambda functions, you can use `APIGatewayRestResolver`.
 
 Here's an example on how we can handle the `/todos` path.
 
-???+ info
-    We automatically serialize `Dict` responses as JSON, trim whitespace for compact responses, and set content-type to `application/json`.
+???+ info "Trailing slash in routes"
+    For `APIGatewayRestResolver`, we seamless handle routes with a trailing slash (`/todos/`).
 
 === "getting_started_rest_api_resolver.py"
 

tests/e2e/event_handler/handlers/alb_handler.py

@@ -2,9 +2,12 @@
 
 app = ALBResolver()
 
+# The reason we use post is that whoever is writing tests can easily assert on the
+# content being sent (body, headers, cookies, content-type) to reduce cognitive load.
+
 
 @app.post("/todos")
-def hello():
+def todos():
     payload = app.current_event.json_body
 
     body = payload.get("body", "Hello World")

tests/e2e/event_handler/handlers/api_gateway_http_handler.py

@@ -6,9 +6,12 @@
 
 app = APIGatewayHttpResolver()
 
+# The reason we use post is that whoever is writing tests can easily assert on the
+# content being sent (body, headers, cookies, content-type) to reduce cognitive load.
+
 
 @app.post("/todos")
-def hello():
+def todos():
     payload = app.current_event.json_body
 
     body = payload.get("body", "Hello World")

tests/e2e/event_handler/handlers/api_gateway_rest_handler.py

@@ -6,9 +6,12 @@
 
 app = APIGatewayRestResolver()
 
+# The reason we use post is that whoever is writing tests can easily assert on the
+# content being sent (body, headers, cookies, content-type) to reduce cognitive load.
+
 
 @app.post("/todos")
-def hello():
+def todos():
     payload = app.current_event.json_body
 
     body = payload.get("body", "Hello World")

tests/e2e/event_handler/handlers/lambda_function_url_handler.py

@@ -6,9 +6,12 @@
 
 app = LambdaFunctionUrlResolver()
 
+# The reason we use post is that whoever is writing tests can easily assert on the
+# content being sent (body, headers, cookies, content-type) to reduce cognitive load.
+
 
 @app.post("/todos")
-def hello():
+def todos():
     payload = app.current_event.json_body
 
     body = payload.get("body", "Hello World")

tests/e2e/event_handler/test_paths_ending_with_slash.py

@@ -0,0 +1,99 @@
+import pytest
+from requests import HTTPError, Request
+
+from tests.e2e.utils import data_fetcher
+
+
+@pytest.fixture
+def alb_basic_listener_endpoint(infrastructure: dict) -> str:
+    dns_name = infrastructure.get("ALBDnsName")
+    port = infrastructure.get("ALBBasicListenerPort", "")
+    return f"http://{dns_name}:{port}"
+
+
+@pytest.fixture
+def alb_multi_value_header_listener_endpoint(infrastructure: dict) -> str:
+    dns_name = infrastructure.get("ALBDnsName")
+    port = infrastructure.get("ALBMultiValueHeaderListenerPort", "")
+    return f"http://{dns_name}:{port}"
+
+
+@pytest.fixture
+def apigw_rest_endpoint(infrastructure: dict) -> str:
+    return infrastructure.get("APIGatewayRestUrl", "")
+
+
+@pytest.fixture
+def apigw_http_endpoint(infrastructure: dict) -> str:
+    return infrastructure.get("APIGatewayHTTPUrl", "")
+
+
+@pytest.fixture
+def lambda_function_url_endpoint(infrastructure: dict) -> str:
+    return infrastructure.get("LambdaFunctionUrl", "")
+
+
+def test_api_gateway_rest_trailing_slash(apigw_rest_endpoint):
+    # GIVEN API URL ends in a trailing slash
+    url = f"{apigw_rest_endpoint}todos/"
+    body = "Hello World"
+
+    # WHEN
+    response = data_fetcher.get_http_response(
+        Request(
+            method="POST",
+            url=url,
+            json={"body": body},
+        )
+    )
+
+    # THEN expect a HTTP 200 response
+    assert response.status_code == 200
+
+
+def test_api_gateway_http_trailing_slash(apigw_http_endpoint):
+    # GIVEN the URL for the API ends in a trailing slash API gateway should return a 404
+    url = f"{apigw_http_endpoint}todos/"
+    body = "Hello World"
+
+    # WHEN calling an invalid URL (with trailing slash) expect HTTPError exception from data_fetcher
+    with pytest.raises(HTTPError):
+        data_fetcher.get_http_response(
+            Request(
+                method="POST",
+                url=url,
+                json={"body": body},
+            )
+        )
+
+
+def test_lambda_function_url_trailing_slash(lambda_function_url_endpoint):
+    # GIVEN the URL for the API ends in a trailing slash it should behave as if there was not one
+    url = f"{lambda_function_url_endpoint}todos/"  # the function url endpoint already has the trailing /
+    body = "Hello World"
+
+    # WHEN calling an invalid URL (with trailing slash) expect HTTPError exception from data_fetcher
+    with pytest.raises(HTTPError):
+        data_fetcher.get_http_response(
+            Request(
+                method="POST",
+                url=url,
+                json={"body": body},
+            )
+        )
+
+
+def test_alb_url_trailing_slash(alb_multi_value_header_listener_endpoint):
+    # GIVEN url has a trailing slash - it should behave as if there was not one
+    url = f"{alb_multi_value_header_listener_endpoint}/todos/"
+    body = "Hello World"
+
+    # WHEN calling an invalid URL (with trailing slash) expect HTTPError exception from data_fetcher
+    with pytest.raises(HTTPError):
+        data_fetcher.get_http_response(
+            Request(
+                method="POST",
+                url=url,
+                json={"body": body},
+            )
+        )

tests/events/albEventPathTrailingSlash.json

@@ -0,0 +1,28 @@
+{
+    "requestContext": {
+      "elb": {
+        "targetGroupArn": "arn:aws:elasticloadbalancing:us-east-2:123456789012:targetgroup/lambda-279XGJDqGZ5rsrHC2Fjr/49e9d65c45c6791a"
+      }
+    },
+    "httpMethod": "GET",
+    "path": "/lambda/",
+    "queryStringParameters": {
+      "query": "1234ABCD"
+    },
+    "headers": {
+      "accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8",
+      "accept-encoding": "gzip",
+      "accept-language": "en-US,en;q=0.9",
+      "connection": "keep-alive",
+      "host": "lambda-alb-123578498.us-east-2.elb.amazonaws.com",
+      "upgrade-insecure-requests": "1",
+      "user-agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.98 Safari/537.36",
+      "x-amzn-trace-id": "Root=1-5c536348-3d683b8b04734faae651f476",
+      "x-forwarded-for": "72.12.164.125",
+      "x-forwarded-port": "80",
+      "x-forwarded-proto": "http",
+      "x-imforwards": "20"
+    },
+    "body": "Test",
+    "isBase64Encoded": false
+  }

tests/events/apiGatewayProxyEventPathTrailingSlash.json

@@ -0,0 +1,80 @@
+{
+    "version": "1.0",
+    "resource": "/my/path",
+    "path": "/my/path/",
+    "httpMethod": "GET",
+    "headers": {
+      "Header1": "value1",
+      "Header2": "value2"
+    },
+    "multiValueHeaders": {
+      "Header1": [
+        "value1"
+      ],
+      "Header2": [
+        "value1",
+        "value2"
+      ]
+    },
+    "queryStringParameters": {
+      "parameter1": "value1",
+      "parameter2": "value"
+    },
+    "multiValueQueryStringParameters": {
+      "parameter1": [
+        "value1",
+        "value2"
+      ],
+      "parameter2": [
+        "value"
+      ]
+    },
+    "requestContext": {
+      "accountId": "123456789012",
+      "apiId": "id",
+      "authorizer": {
+        "claims": null,
+        "scopes": null
+      },
+      "domainName": "id.execute-api.us-east-1.amazonaws.com",
+      "domainPrefix": "id",
+      "extendedRequestId": "request-id",
+      "httpMethod": "GET",
+      "identity": {
+        "accessKey": null,
+        "accountId": null,
+        "caller": null,
+        "cognitoAuthenticationProvider": null,
+        "cognitoAuthenticationType": null,
+        "cognitoIdentityId": null,
+        "cognitoIdentityPoolId": null,
+        "principalOrgId": null,
+        "sourceIp": "192.168.0.1/32",
+        "user": null,
+        "userAgent": "user-agent",
+        "userArn": null,
+        "clientCert": {
+          "clientCertPem": "CERT_CONTENT",
+          "subjectDN": "www.example.com",
+          "issuerDN": "Example issuer",
+          "serialNumber": "a1:a1:a1:a1:a1:a1:a1:a1:a1:a1:a1:a1:a1:a1:a1:a1",
+          "validity": {
+            "notBefore": "May 28 12:30:02 2019 GMT",
+            "notAfter": "Aug  5 09:36:04 2021 GMT"
+          }
+        }
+      },
+      "path": "/my/path",
+      "protocol": "HTTP/1.1",
+      "requestId": "id=",
+      "requestTime": "04/Mar/2020:19:15:17 +0000",
+      "requestTimeEpoch": 1583349317135,
+      "resourceId": null,
+      "resourcePath": "/my/path",
+      "stage": "$default"
+    },
+    "pathParameters": null,
+    "stageVariables": null,
+    "body": "Hello from Lambda!",
+    "isBase64Encoded": true
+  }