runtime_error.rs

/*
 * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 * SPDX-License-Identifier: Apache-2.0
 */

//! Runtime error type.
//!
//! This module contains the [`RuntimeError`] type.
//!
//! As opposed to rejection types (see [`crate::proto::rest_json_1::rejection`]), which are an internal detail about
//! the framework, `RuntimeError` is surfaced to clients in HTTP responses: indeed, it implements
//! [`RuntimeError::into_response`]. Rejections can be "grouped" and converted into a
//! specific `RuntimeError` kind: for example, all request rejections due to serialization issues
//! can be conflated under the [`RuntimeError::Serialization`] enum variant.
//!
//! The HTTP response representation of the specific `RuntimeError` is protocol-specific: for
//! example, the runtime error in the [`crate::proto::rest_json_1`] protocol sets the `X-Amzn-Errortype` header.
//!
//! Generated code works always works with [`crate::rejection`] types when deserializing requests
//! and serializing response. Just before a response needs to be sent, the generated code looks up
//! and converts into the corresponding `RuntimeError`, and then it uses the its
//! [`RuntimeError::into_response`] method to render and send a response.
//!
//! This module hosts the `RuntimeError` type _specific_ to the [`crate::proto::rest_json_1`] protocol, but
//! the paragraphs above apply to _all_ protocol-specific rejection types.
//!
//! Similarly, `RuntimeError` variants are exhaustively documented solely in this module if they have
//! direct counterparts in other protocols. This is to avoid documentation getting out of date.
//!
//! Consult `crate::proto::$protocolName::runtime_error` for the `RuntimeError` type for other protocols.

use super::rejection::RequestRejection;
use super::rejection::ResponseRejection;
use super::RestJson1;
use crate::extension::RuntimeErrorExtension;
use crate::response::IntoResponse;
use crate::runtime_error::InternalFailureException;
use crate::runtime_error::INVALID_HTTP_RESPONSE_FOR_RUNTIME_ERROR_PANIC_MESSAGE;
use http::StatusCode;

#[derive(Debug)]
pub enum RuntimeError {
    /// Request failed to deserialize or response failed to serialize.
    Serialization(crate::Error),
    /// As of writing, this variant can only occur upon failure to extract an
    /// [`crate::extension::Extension`] from the request.
    InternalFailure(crate::Error),
    /// Request contained an `Accept` header with a MIME type, and the server cannot return a response
    /// body adhering to that MIME type.
    NotAcceptable,
    /// The request does not contain the expected `Content-Type` header value.
    UnsupportedMediaType,
    /// Operation input contains data that does not adhere to the modeled [constraint traits].
    /// [constraint traits]: <https://awslabs.github.io/smithy/2.0/spec/constraint-traits.html>
    Validation(String),
}

impl RuntimeError {
    /// String representation of the `RuntimeError` kind.
    /// Used as the value passed to construct an [`crate::extension::RuntimeErrorExtension`].
    /// Used as the value of the `X-Amzn-Errortype` header.
    pub fn name(&self) -> &'static str {
        match self {
            Self::Serialization(_) => "SerializationException",
            Self::InternalFailure(_) => "InternalFailureException",
            Self::NotAcceptable => "NotAcceptableException",
            Self::UnsupportedMediaType => "UnsupportedMediaTypeException",
            Self::Validation(_) => "ValidationException",
        }
    }

    pub fn status_code(&self) -> StatusCode {
        match self {
            Self::Serialization(_) => StatusCode::BAD_REQUEST,
            Self::InternalFailure(_) => StatusCode::INTERNAL_SERVER_ERROR,
            Self::NotAcceptable => StatusCode::NOT_ACCEPTABLE,
            Self::UnsupportedMediaType => StatusCode::UNSUPPORTED_MEDIA_TYPE,
            Self::Validation(_) => StatusCode::BAD_REQUEST,
        }
    }
}

impl IntoResponse<RestJson1> for InternalFailureException {
    fn into_response(self) -> http::Response<crate::body::BoxBody> {
        IntoResponse::<RestJson1>::into_response(RuntimeError::InternalFailure(crate::Error::new(String::new())))
    }
}

impl IntoResponse<RestJson1> for RuntimeError {
    fn into_response(self) -> http::Response<crate::body::BoxBody> {
        let res = http::Response::builder()
            .status(self.status_code())
            .header("Content-Type", "application/json")
            .header("X-Amzn-Errortype", self.name())
            .extension(RuntimeErrorExtension::new(self.name().to_string()));

        let body = match self {
            RuntimeError::Validation(reason) => crate::body::to_boxed(reason),
            _ => crate::body::to_boxed("{}"),
        };

        res.body(body)
            .expect(INVALID_HTTP_RESPONSE_FOR_RUNTIME_ERROR_PANIC_MESSAGE)
    }
}

impl From<ResponseRejection> for RuntimeError {
    fn from(err: ResponseRejection) -> Self {
        Self::Serialization(crate::Error::new(err))
    }
}

impl From<RequestRejection> for RuntimeError {
    fn from(err: RequestRejection) -> Self {
        match err {
            RequestRejection::MissingContentType(_reason) => Self::UnsupportedMediaType,
            RequestRejection::ConstraintViolation(reason) => Self::Validation(reason),
            RequestRejection::NotAcceptable(_reason) => Self::NotAcceptable,
            _ => Self::Serialization(crate::Error::new(err)),
        }
    }
}