1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296

use futures_util::future::FusedFuture;
use std::fmt::{Debug, Display};
use std::future::Future;
use std::pin::Pin;
use std::task::{Context, Poll};

use hyper::{Body, Response, StatusCode};
use log::{debug, trace};

use crate::handler::IntoResponse;
use crate::helpers::http::response::create_empty_response;
use crate::state::{request_id, State};

/// Describes an error which occurred during handler execution, and allows the creation of a HTTP
/// `Response`.
#[derive(Debug)]
pub struct HandlerError {
    status_code: StatusCode,
    cause: anyhow::Error,
}

/// Convert a generic `anyhow::Error` into a `HandlerError`, similar as you would a concrete error
/// type with `into_handler_error()`.
impl<E> From<E> for HandlerError
where
    E: Into<anyhow::Error> + Display,
{
    fn from(error: E) -> HandlerError {
        trace!(" converting Error to HandlerError: {}", error);

        HandlerError {
            status_code: StatusCode::INTERNAL_SERVER_ERROR,
            cause: error.into(),
        }
    }
}

impl HandlerError {
    /// Returns the HTTP status code associated with this `HandlerError`.
    pub fn status(&self) -> StatusCode {
        self.status_code
    }

    /// Sets the HTTP status code of the response which is generated by the `IntoResponse`
    /// implementation.
    ///
    /// ```rust
    /// # use std::pin::Pin;
    /// #
    /// # use futures_util::future::{self, FutureExt};
    /// # use hyper::StatusCode;
    /// # use gotham::state::State;
    /// # use gotham::handler::{HandlerError, HandlerFuture};
    /// # use gotham::test::TestServer;
    /// #
    /// fn handler(state: State) -> Pin<Box<HandlerFuture>> {
    ///     // It's OK if this is bogus, we just need something to convert into a `HandlerError`.
    ///     let io_error = std::io::Error::last_os_error();
    ///
    ///     let handler_error = HandlerError::from(io_error).with_status(StatusCode::IM_A_TEAPOT);
    ///
    ///     future::err((state, handler_error)).boxed()
    /// }
    ///
    /// # fn main() {
    /// #
    /// let test_server = TestServer::new(|| Ok(handler)).unwrap();
    /// let response = test_server
    ///     .client()
    ///     .get("http://example.com/")
    ///     .perform()
    ///     .unwrap();
    /// assert_eq!(response.status(), StatusCode::IM_A_TEAPOT);
    /// #
    /// # }
    /// ```
    pub fn with_status(self, status_code: StatusCode) -> HandlerError {
        HandlerError {
            status_code,
            ..self
        }
    }

    /// Returns the cause of this error by reference.
    pub fn cause(&self) -> &anyhow::Error {
        &self.cause
    }

    /// Returns the cause of this error.
    pub fn into_cause(self) -> anyhow::Error {
        self.cause
    }

    /// Attempt to downcast the cause by reference.
    pub fn downcast_cause_ref<E>(&self) -> Option<&E>
    where
        E: Display + Debug + Send + Sync + 'static,
    {
        self.cause.downcast_ref()
    }

    /// Attempt to downcast the cause by mutable reference.
    pub fn downcast_cause_mut<E>(&mut self) -> Option<&mut E>
    where
        E: Display + Debug + Send + Sync + 'static,
    {
        self.cause.downcast_mut()
    }
}

impl IntoResponse for HandlerError {
    fn into_response(self, state: &State) -> Response<Body> {
        debug!(
            "[{}] HandlerError generating {} {} response: {}",
            request_id(state),
            self.status_code.as_u16(),
            self.status_code
                .canonical_reason()
                .unwrap_or("(unregistered)",),
            self.cause
        );

        create_empty_response(state, self.status_code)
    }
}

/// This trait allows you to convert a `Result`'s `Err` case into a handler error with the given
/// status code. This is handy if you want to specify the status code but still use the `?`
/// shorthand.
///
/// ```rust
/// # extern crate gotham;
/// # use gotham::anyhow::anyhow;
/// # use gotham::handler::{HandlerError, MapHandlerError};
/// # use gotham::hyper::StatusCode;
/// fn handler() -> Result<(), HandlerError> {
///     let result = Err(anyhow!("just a test"));
///     result.map_err_with_status(StatusCode::IM_A_TEAPOT)?;
///     unreachable!()
/// }
///
/// # #[allow(non_snake_case)]
/// # fn Err<T>(err: T) -> Result<(), T> {
/// #   Result::Err(err)
/// # }
/// # fn main() {
/// let response = handler();
/// assert_eq!(
///     response.map_err(|err| err.status()),
///     Err(StatusCode::IM_A_TEAPOT)
/// );
/// # }
/// ```
pub trait MapHandlerError<T> {
    /// Equivalent of `map_err(|err| HandlerError::from(err).with_status(status_code))`.
    fn map_err_with_status(self, status_code: StatusCode) -> Result<T, HandlerError>;
}

impl<T, E> MapHandlerError<T> for Result<T, E>
where
    E: Into<anyhow::Error> + Display,
{
    fn map_err_with_status(self, status_code: StatusCode) -> Result<T, HandlerError> {
        self.map_err(|err| {
            trace!(" converting Error to HandlerError: {}", err);
            HandlerError {
                status_code,
                cause: err.into(),
            }
        })
    }
}

// The future for `map_err_with_status`.
#[pin_project::pin_project(project = MapErrWithStatusProj, project_replace = MapErrWithStatusProjOwn)]
#[derive(Debug)]
#[must_use = "futures do nothing unless you `.await` or poll them"]
pub enum MapErrWithStatus<F> {
    Incomplete {
        #[pin]
        future: F,
        status: StatusCode,
    },
    Complete,
}

impl<F> MapErrWithStatus<F> {
    fn new(future: F, status: StatusCode) -> Self {
        Self::Incomplete { future, status }
    }
}

impl<F, T, E> FusedFuture for MapErrWithStatus<F>
where
    F: Future<Output = Result<T, E>>,
    E: Into<anyhow::Error> + Display,
{
    fn is_terminated(&self) -> bool {
        matches!(self, Self::Complete)
    }
}

impl<F, T, E> Future for MapErrWithStatus<F>
where
    F: Future<Output = Result<T, E>>,
    E: Into<anyhow::Error> + Display,
{
    type Output = Result<T, HandlerError>;

    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        match self.as_mut().project() {
            MapErrWithStatusProj::Incomplete { future, .. } => {
                let output = match future.poll(cx) {
                    Poll::Ready(output) => output,
                    Poll::Pending => return Poll::Pending,
                };
                match self.project_replace(MapErrWithStatus::Complete) {
                    MapErrWithStatusProjOwn::Incomplete { status, .. } => {
                        Poll::Ready(output.map_err_with_status(status))
                    }
                    MapErrWithStatusProjOwn::Complete => unreachable!(),
                }
            }
            MapErrWithStatusProj::Complete => {
                panic!("MapErrWithStatus must not be polled after it returned `Poll::Ready`")
            }
        }
    }
}

/// This trait allows you to convert a `Result`'s `Err` case into a handler error with the given
/// status code. This is handy if you want to specify the status code but still use the `?`
/// shorthand.
/// ```rust
/// # use futures_executor::block_on;
/// # use gotham::anyhow::anyhow;
/// # use gotham::handler::{HandlerError, MapHandlerErrorFuture};
/// # use gotham::hyper::StatusCode;
/// # use std::future::Future;
/// fn handler() -> impl Future<Output = Result<(), HandlerError>> {
///     let result = async { Err(anyhow!("just a test")) };
///     result.map_err_with_status(StatusCode::IM_A_TEAPOT)
/// }
///
/// # #[allow(non_snake_case)]
/// # fn Err<T>(err: T) -> Result<(), T> {
/// #   Result::Err(err)
/// # }
/// # fn main() {
/// let response = block_on(handler());
/// assert_eq!(
///     response.map_err(|err| err.status()),
///     Err(StatusCode::IM_A_TEAPOT)
/// );
/// # }
/// ```
pub trait MapHandlerErrorFuture {
    /// Equivalent of `map_err(|err| HandlerError::from(err).with_status(status_code))`.
    fn map_err_with_status(self, status_code: StatusCode) -> MapErrWithStatus<Self>
    where
        Self: Sized;
}

impl<T, E, F> MapHandlerErrorFuture for F
where
    E: Into<anyhow::Error> + Display,
    F: Future<Output = Result<T, E>>,
{
    fn map_err_with_status(self, status_code: StatusCode) -> MapErrWithStatus<Self> {
        MapErrWithStatus::new(self, status_code)
    }
}

#[cfg(test)]
mod test {
    use super::*;
    use std::io;
    use thiserror::Error;

    #[derive(Debug, Error)]
    #[error("Dummy Error")]
    struct DummyError;

    fn error_prone() -> Result<(), HandlerError> {
        Err(DummyError.into())
    }

    #[test]
    fn test_error_downcast() {
        let mut err = error_prone().unwrap_err();
        assert!(err.downcast_cause_ref::<DummyError>().is_some());
        assert!(err.downcast_cause_mut::<DummyError>().is_some());
        assert!(err.downcast_cause_ref::<io::Error>().is_none());
        assert!(err.downcast_cause_mut::<io::Error>().is_none());
    }
}