feat(event_handler): generate OpenAPI specifications and validate input/output

aws_lambda_powertools/event_handler/lambda_function_url.py

@@ -52,5 +52,13 @@ def __init__(
         debug: Optional[bool] = None,
         serializer: Optional[Callable[[Dict], str]] = None,
         strip_prefixes: Optional[List[Union[str, Pattern]]] = None,
+        enable_validation: bool = False,
     ):
-        super().__init__(ProxyEventType.LambdaFunctionUrlEvent, cors, debug, serializer, strip_prefixes)
+        super().__init__(
+            ProxyEventType.LambdaFunctionUrlEvent,
+            cors,
+            debug,
+            serializer,
+            strip_prefixes,
+            enable_validation,
+        )

aws_lambda_powertools/event_handler/middlewares/openapi_validation.py

@@ -0,0 +1,342 @@
+import dataclasses
+import json
+import logging
+from copy import deepcopy
+from typing import Any, Dict, List, Mapping, Optional, Sequence, Tuple
+
+from pydantic import BaseModel
+
+from aws_lambda_powertools.event_handler import Response
+from aws_lambda_powertools.event_handler.api_gateway import Route
+from aws_lambda_powertools.event_handler.middlewares import BaseMiddlewareHandler, NextMiddleware
+from aws_lambda_powertools.event_handler.openapi.compat import (
+    ModelField,
+    _model_dump,
+    _normalize_errors,
+    _regenerate_error_with_loc,
+    get_missing_field_error,
+)
+from aws_lambda_powertools.event_handler.openapi.encoders import jsonable_encoder
+from aws_lambda_powertools.event_handler.openapi.exceptions import RequestValidationError
+from aws_lambda_powertools.event_handler.openapi.params import Param
+from aws_lambda_powertools.event_handler.openapi.types import IncEx
+from aws_lambda_powertools.event_handler.types import EventHandlerInstance
+
+logger = logging.getLogger(__name__)
+
+
+class OpenAPIValidationMiddleware(BaseMiddlewareHandler):
+    """
+    OpenAPIValidationMiddleware is a middleware that validates the request against the OpenAPI schema defined by the
+    Lambda handler. It also validates the response against the OpenAPI schema defined by the Lambda handler. It
+    should not be used directly, but rather through the `enable_validation` parameter of the `ApiGatewayResolver`.
+
+    Examples
+    --------
+
+    ```python
+    from typing import List
+
+    from pydantic import BaseModel
+
+    from aws_lambda_powertools.event_handler.api_gateway import (
+        APIGatewayRestResolver,
+    )
+
+    class Todo(BaseModel):
+      name: str
+
+    app = APIGatewayRestResolver(enable_validation=True)
+
+    @app.get("/todos")
+    def get_todos(): List[Todo]:
+      return [Todo(name="hello world")]
+    ```
+    """
+
+    def handler(self, app: EventHandlerInstance, next_middleware: NextMiddleware) -> Response:
+        logger.debug("OpenAPIValidationMiddleware handler")
+
+        route: Route = app.context["_route"]
+
+        values: Dict[str, Any] = {}
+        errors: List[Any] = []
+
+        try:
+            # Process path values, which can be found on the route_args
+            path_values, path_errors = _request_params_to_args(
+                route.dependant.path_params,
+                app.context["_route_args"],
+            )
+
+            # Process query values
+            query_values, query_errors = _request_params_to_args(
+                route.dependant.query_params,
+                app.current_event.query_string_parameters or {},
+            )
+
+            values.update(path_values)
+            values.update(query_values)
+            errors += path_errors + query_errors
+
+            # Process the request body, if it exists
+            if route.dependant.body_params:
+                (body_values, body_errors) = _request_body_to_args(
+                    required_params=route.dependant.body_params,
+                    received_body=self._get_body(app),
+                )
+                values.update(body_values)
+                errors.extend(body_errors)
+
+            if errors:
+                # Raise the validation errors
+                raise RequestValidationError(_normalize_errors(errors))
+            else:
+                # Re-write the route_args with the validated values, and call the next middleware
+                app.context["_route_args"] = values
+                response = next_middleware(app)
+
+                # Process the response body if it exists
+                raw_response = jsonable_encoder(response.body)
+
+                # Validate and serialize the response
+                return self._serialize_response(field=route.dependant.return_param, response_content=raw_response)
+        except RequestValidationError as e:
+            return Response(
+                status_code=422,
+                content_type="application/json",
+                body=json.dumps({"detail": e.errors()}),
+            )
+
+    def _serialize_response(
+        self,
+        *,
+        field: Optional[ModelField] = None,
+        response_content: Any,
+        include: Optional[IncEx] = None,
+        exclude: Optional[IncEx] = None,
+        by_alias: bool = True,
+        exclude_unset: bool = False,
+        exclude_defaults: bool = False,
+        exclude_none: bool = False,
+    ) -> Any:
+        """
+        Serialize the response content according to the field type.
+        """
+        if field:
+            errors: List[Dict[str, Any]] = []
+            # MAINTENANCE: remove this when we drop pydantic v1
+            if not hasattr(field, "serializable"):
+                response_content = self._prepare_response_content(
+                    response_content,
+                    exclude_unset=exclude_unset,
+                    exclude_defaults=exclude_defaults,
+                    exclude_none=exclude_none,
+                )
+
+            value = _validate_field(field=field, value=response_content, loc=("response",), existing_errors=errors)
+            if errors:
+                raise RequestValidationError(errors=_normalize_errors(errors), body=response_content)
+
+            if hasattr(field, "serialize"):
+                return field.serialize(
+                    value,
+                    include=include,
+                    exclude=exclude,
+                    by_alias=by_alias,
+                    exclude_unset=exclude_unset,
+                    exclude_defaults=exclude_defaults,
+                    exclude_none=exclude_none,
+                )
+
+            return jsonable_encoder(
+                value,
+                include=include,
+                exclude=exclude,
+                by_alias=by_alias,
+                exclude_unset=exclude_unset,
+                exclude_defaults=exclude_defaults,
+                exclude_none=exclude_none,
+            )
+        else:
+            # Just serialize the response content returned from the handler
+            return jsonable_encoder(response_content)
+
+    def _prepare_response_content(
+        self,
+        res: Any,
+        *,
+        exclude_unset: bool,
+        exclude_defaults: bool = False,
+        exclude_none: bool = False,
+    ) -> Any:
+        """
+        Prepares the response content for serialization.
+        """
+        if isinstance(res, BaseModel):
+            return _model_dump(
+                res,
+                by_alias=True,
+                exclude_unset=exclude_unset,
+                exclude_defaults=exclude_defaults,
+                exclude_none=exclude_none,
+            )
+        elif isinstance(res, list):
+            return [
+                self._prepare_response_content(item, exclude_unset=exclude_unset, exclude_defaults=exclude_defaults)
+                for item in res
+            ]
+        elif isinstance(res, dict):
+            return {
+                k: self._prepare_response_content(v, exclude_unset=exclude_unset, exclude_defaults=exclude_defaults)
+                for k, v in res.items()
+            }
+        elif dataclasses.is_dataclass(res):
+            return dataclasses.asdict(res)
+        return res
+
+    def _get_body(self, app: EventHandlerInstance) -> Dict[str, Any]:
+        """
+        Get the request body from the event, and parse it as JSON.
+        """
+
+        content_type_value = app.current_event.get_header_value("content-type")
+        if not content_type_value or content_type_value.startswith("application/json"):
+            try:
+                return app.current_event.json_body
+            except json.JSONDecodeError as e:
+                raise RequestValidationError(
+                    [
+                        {
+                            "type": "json_invalid",
+                            "loc": ("body", e.pos),
+                            "msg": "JSON decode error",
+                            "input": {},
+                            "ctx": {"error": e.msg},
+                        },
+                    ],
+                    body=e.doc,
+                ) from e
+        else:
+            raise NotImplementedError("Only JSON body is supported")
+
+
+def _request_params_to_args(
+    required_params: Sequence[ModelField],
+    received_params: Mapping[str, Any],
+) -> Tuple[Dict[str, Any], List[Any]]:
+    """
+    Convert the request params to a dictionary of values using validation, and returns a list of errors.
+    """
+    values = {}
+    errors = []
+
+    for field in required_params:
+        value = received_params.get(field.alias)
+
+        field_info = field.field_info
+        if not isinstance(field_info, Param):
+            raise AssertionError(f"Expected Param field_info, got {field_info}")
+
+        loc = (field_info.in_.value, field.alias)
+
+        # If we don't have a value, see if it's required or has a default
+        if value is None:
+            if field.required:
+                errors.append(get_missing_field_error(loc=loc))
+            else:
+                values[field.name] = deepcopy(field.default)
+            continue
+
+        # Finally, validate the value
+        values[field.name] = _validate_field(field=field, value=value, loc=loc, existing_errors=errors)
+
+    return values, errors
+
+
+def _request_body_to_args(
+    required_params: List[ModelField],
+    received_body: Optional[Dict[str, Any]],
+) -> Tuple[Dict[str, Any], List[Dict[str, Any]]]:
+    """
+    Convert the request body to a dictionary of values using validation, and returns a list of errors.
+    """
+    values: Dict[str, Any] = {}
+    errors: List[Dict[str, Any]] = []
+
+    received_body, field_alias_omitted = _get_embed_body(
+        field=required_params[0],
+        required_params=required_params,
+        received_body=received_body,
+    )
+
+    for field in required_params:
+        # This sets the location to:
+        # { "user": { object } } if field.alias == user
+        # { { object } if field_alias is omitted
+        loc: Tuple[str, ...] = ("body", field.alias)
+        if field_alias_omitted:
+            loc = ("body",)
+
+        value: Optional[Any] = None
+
+        # Now that we know what to look for, try to get the value from the received body
+        if received_body is not None:
+            try:
+                value = received_body.get(field.alias)
+            except AttributeError:
+                errors.append(get_missing_field_error(loc))
+                continue
+
+        # Determine if the field is required
+        if value is None:
+            if field.required:
+                errors.append(get_missing_field_error(loc))
+            else:
+                values[field.name] = deepcopy(field.default)
+            continue
+
+        # MAINTENANCE: Handle byte and file fields
+
+        # Finally, validate the value
+        values[field.name] = _validate_field(field=field, value=value, loc=loc, existing_errors=errors)
+
+    return values, errors
+
+
+def _validate_field(
+    *,
+    field: ModelField,
+    value: Any,
+    loc: Tuple[str, ...],
+    existing_errors: List[Dict[str, Any]],
+):
+    """
+    Validate a field, and append any errors to the existing_errors list.
+    """
+    validated_value, errors = field.validate(value, value, loc=loc)
+
+    if isinstance(errors, list):
+        processed_errors = _regenerate_error_with_loc(errors=errors, loc_prefix=())
+        existing_errors.extend(processed_errors)
+    elif errors:
+        existing_errors.append(errors)
+
+    return validated_value
+
+
+def _get_embed_body(
+    *,
+    field: ModelField,
+    required_params: List[ModelField],
+    received_body: Optional[Dict[str, Any]],
+) -> Tuple[Optional[Dict[str, Any]], bool]:
+    field_info = field.field_info
+    embed = getattr(field_info, "embed", None)
+
+    # If the field is an embed, and the field alias is omitted, we need to wrap the received body in the field alias.
+    field_alias_omitted = len(required_params) == 1 and not embed
+    if field_alias_omitted:
+        received_body = {field.alias: received_body}
+
+    return received_body, field_alias_omitted