topcoat-router 0.6.0

A modular, batteries-included Rust web framework for server-rendered apps.
Documentation 
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

use std::{
    convert::Infallible,
    pin::Pin,
    task::{Context, Poll},
};

use bytes::Bytes;
use http_body::{Frame, SizeHint};
use http_body_util::{
    BodyExt, BodyStream, Empty, Full, LengthLimitError, Limited, combinators::UnsyncBoxBody,
};
use topcoat_core::error::Result;

use crate::error::{bad_request, content_too_large};

/// A boxed error type used by the response body machinery.
pub type BoxError = Box<dyn std::error::Error + Send + Sync>;

/// The HTTP body type used for both requests and responses.
#[must_use]
pub struct Body(UnsyncBoxBody<Bytes, BoxError>);

impl Body {
    /// Creates an empty body.
    pub fn empty() -> Self {
        Self::from(Bytes::new())
    }

    /// Wraps any [`http_body::Body`] that yields [`Bytes`].
    pub fn new<B>(body: B) -> Self
    where
        B: http_body::Body<Data = Bytes> + Send + 'static,
        B::Error: Into<BoxError>,
    {
        Self(body.map_err(Into::into).boxed_unsync())
    }

    /// Consumes the body, returning a [`Stream`](futures_core::Stream) of its
    /// data frames.
    pub fn into_data_stream(self) -> BodyDataStream {
        BodyDataStream(BodyStream::new(self))
    }
}

impl Default for Body {
    fn default() -> Self {
        Self::empty()
    }
}

impl From<Bytes> for Body {
    fn from(bytes: Bytes) -> Self {
        Self(
            Full::new(bytes)
                .map_err(|never: Infallible| match never {})
                .boxed_unsync(),
        )
    }
}

impl From<()> for Body {
    fn from((): ()) -> Self {
        Self(
            Empty::new()
                .map_err(|never: Infallible| match never {})
                .boxed_unsync(),
        )
    }
}

impl From<Vec<u8>> for Body {
    fn from(value: Vec<u8>) -> Self {
        Self::from(Bytes::from(value))
    }
}

impl From<&'static [u8]> for Body {
    fn from(value: &'static [u8]) -> Self {
        Self::from(Bytes::from_static(value))
    }
}

impl From<String> for Body {
    fn from(value: String) -> Self {
        Self::from(Bytes::from(value))
    }
}

impl From<&'static str> for Body {
    fn from(value: &'static str) -> Self {
        Self::from(Bytes::from_static(value.as_bytes()))
    }
}

impl http_body::Body for Body {
    type Data = Bytes;
    type Error = BoxError;

    fn poll_frame(
        mut self: Pin<&mut Self>,
        cx: &mut Context<'_>,
    ) -> Poll<Option<Result<Frame<Self::Data>, Self::Error>>> {
        Pin::new(&mut self.0).poll_frame(cx)
    }

    fn size_hint(&self) -> SizeHint {
        self.0.size_hint()
    }

    fn is_end_stream(&self) -> bool {
        self.0.is_end_stream()
    }
}

impl std::fmt::Debug for Body {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("Body").finish_non_exhaustive()
    }
}

/// A [`Stream`](futures_core::Stream) over the data frames of a [`Body`],
/// yielding the raw [`Bytes`] of each frame.
#[must_use]
pub struct BodyDataStream(BodyStream<Body>);

impl futures_core::Stream for BodyDataStream {
    type Item = Result<Bytes, BoxError>;

    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
        loop {
            return match Pin::new(&mut self.0).poll_next(cx) {
                Poll::Ready(Some(Ok(frame))) => match frame.into_data() {
                    Ok(data) => Poll::Ready(Some(Ok(data))),
                    Err(_frame) => continue,
                },
                Poll::Ready(Some(Err(error))) => Poll::Ready(Some(Err(error))),
                Poll::Ready(None) => Poll::Ready(None),
                Poll::Pending => Poll::Pending,
            };
        }
    }
}

/// Collects an entire [`Body`] into [`Bytes`], failing if it exceeds `limit`.
///
/// Pass [`usize::MAX`] to read the body without enforcing a limit. When
/// reading a request body, pass the request's
/// [`body_limit`](crate::body_limit) so the configured limit applies.
///
/// # Errors
///
/// Returns a [`ContentTooLargeError`](crate::error::ContentTooLargeError) when
/// the body exceeds `limit` bytes, and a
/// [`BadRequestError`](crate::error::BadRequestError) when reading it fails.
/// Both render themselves as a response, so a
/// [`FromRequest`](crate::request::FromRequest) implementation can propagate them with
/// `?` rather than mapping them by hand.
pub async fn to_bytes(body: Body, limit: usize) -> Result<Bytes> {
    let collected = if limit == usize::MAX {
        body.collect().await
    } else {
        Limited::new(body, limit).collect().await
    };

    match collected {
        Ok(collected) => Ok(collected.to_bytes()),
        Err(error) => Err(match error.downcast::<LengthLimitError>() {
            Ok(_) => content_too_large().into(),
            Err(error) => bad_request(format!("failed to read the body: {error}")).into(),
        }),
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::error::{BadRequestError, ContentTooLargeError};

    /// A body that fails on its first frame, standing in for a connection that
    /// breaks mid-stream.
    struct FailingBody;

    impl http_body::Body for FailingBody {
        type Data = Bytes;
        type Error = BoxError;

        fn poll_frame(
            self: Pin<&mut Self>,
            _cx: &mut Context<'_>,
        ) -> Poll<Option<Result<Frame<Bytes>, BoxError>>> {
            Poll::Ready(Some(Err("body stream broke".into())))
        }
    }

    #[tokio::test]
    async fn a_body_within_the_limit_reads_in_full() {
        let bytes = to_bytes(Body::from("hello"), 1024).await.unwrap();
        assert_eq!(bytes, Bytes::from_static(b"hello"));
    }

    #[tokio::test]
    async fn usize_max_reads_without_enforcing_a_limit() {
        let bytes = to_bytes(Body::from("hello"), usize::MAX).await.unwrap();
        assert_eq!(bytes, Bytes::from_static(b"hello"));
    }

    #[tokio::test]
    async fn a_body_over_the_limit_is_content_too_large() {
        let error = to_bytes(Body::from("hello"), 4).await.unwrap_err();
        assert!(error.is::<ContentTooLargeError>());
    }

    #[tokio::test]
    async fn a_read_failure_is_a_bad_request_carrying_the_cause() {
        // Both branches are covered: a limit installs `Limited` around the
        // body, which boxes the failure a second time.
        for limit in [usize::MAX, 1024] {
            let error = to_bytes(Body::new(FailingBody), limit).await.unwrap_err();
            let error = error
                .downcast::<BadRequestError>()
                .expect("a read failure is a bad request");
            assert_eq!(
                error.description(),
                "failed to read the body: body stream broke"
            );
        }
    }
}