refined error model (#2253)

src/error/response_error.rs

@@ -0,0 +1,144 @@
+//! `ResponseError` trait and foreign impls.
+
+use std::{
+    error::Error as StdError,
+    fmt,
+    io::{self, Write as _},
+};
+
+use actix_http::{body::AnyBody, header, Response, StatusCode};
+use bytes::BytesMut;
+
+use crate::{__downcast_dyn, __downcast_get_type_id};
+use crate::{helpers, HttpResponse};
+
+/// Errors that can generate responses.
+// TODO: add std::error::Error bound when replacement for Box<dyn Error> is found
+pub trait ResponseError: fmt::Debug + fmt::Display {
+    /// Returns appropriate status code for error.
+    ///
+    /// A 500 Internal Server Error is used by default. If [error_response](Self::error_response) is
+    /// also implemented and does not call `self.status_code()`, then this will not be used.
+    fn status_code(&self) -> StatusCode {
+        StatusCode::INTERNAL_SERVER_ERROR
+    }
+
+    /// Creates full response for error.
+    ///
+    /// By default, the generated response uses a 500 Internal Server Error status code, a
+    /// `Content-Type` of `text/plain`, and the body is set to `Self`'s `Display` impl.
+    fn error_response(&self) -> HttpResponse {
+        let mut res = HttpResponse::new(self.status_code());
+
+        let mut buf = BytesMut::new();
+        let _ = write!(helpers::MutWriter(&mut buf), "{}", self);
+
+        res.headers_mut().insert(
+            header::CONTENT_TYPE,
+            header::HeaderValue::from_static("text/plain; charset=utf-8"),
+        );
+
+        res.set_body(AnyBody::from(buf))
+    }
+
+    __downcast_get_type_id!();
+}
+
+__downcast_dyn!(ResponseError);
+
+impl ResponseError for Box<dyn StdError + 'static> {}
+
+#[cfg(feature = "openssl")]
+impl ResponseError for actix_tls::accept::openssl::SslError {}
+
+impl ResponseError for serde::de::value::Error {
+    fn status_code(&self) -> StatusCode {
+        StatusCode::BAD_REQUEST
+    }
+}
+
+impl ResponseError for std::str::Utf8Error {
+    fn status_code(&self) -> StatusCode {
+        StatusCode::BAD_REQUEST
+    }
+}
+
+impl ResponseError for std::io::Error {
+    fn status_code(&self) -> StatusCode {
+        // TODO: decide if these errors should consider not found or permission errors
+        match self.kind() {
+            io::ErrorKind::NotFound => StatusCode::NOT_FOUND,
+            io::ErrorKind::PermissionDenied => StatusCode::FORBIDDEN,
+            _ => StatusCode::INTERNAL_SERVER_ERROR,
+        }
+    }
+}
+
+impl ResponseError for actix_http::error::HttpError {}
+
+impl ResponseError for actix_http::Error {
+    fn status_code(&self) -> StatusCode {
+        // TODO: map error kinds to status code better
+        StatusCode::INTERNAL_SERVER_ERROR
+    }
+
+    fn error_response(&self) -> HttpResponse {
+        HttpResponse::new(self.status_code()).set_body(self.to_string().into())
+    }
+}
+
+impl ResponseError for actix_http::header::InvalidHeaderValue {
+    fn status_code(&self) -> StatusCode {
+        StatusCode::BAD_REQUEST
+    }
+}
+
+impl ResponseError for actix_http::error::ParseError {
+    fn status_code(&self) -> StatusCode {
+        StatusCode::BAD_REQUEST
+    }
+}
+
+impl ResponseError for actix_http::error::BlockingError {}
+
+impl ResponseError for actix_http::error::PayloadError {
+    fn status_code(&self) -> StatusCode {
+        match *self {
+            actix_http::error::PayloadError::Overflow => StatusCode::PAYLOAD_TOO_LARGE,
+            _ => StatusCode::BAD_REQUEST,
+        }
+    }
+}
+
+impl ResponseError for actix_http::ws::ProtocolError {}
+
+impl ResponseError for actix_http::error::ContentTypeError {
+    fn status_code(&self) -> StatusCode {
+        StatusCode::BAD_REQUEST
+    }
+}
+
+impl ResponseError for actix_http::ws::HandshakeError {
+    fn error_response(&self) -> HttpResponse {
+        Response::from(self).into()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_error_casting() {
+        use actix_http::error::{ContentTypeError, PayloadError};
+
+        let err = PayloadError::Overflow;
+        let resp_err: &dyn ResponseError = &err;
+
+        let err = resp_err.downcast_ref::<PayloadError>().unwrap();
+        assert_eq!(err.to_string(), "Payload reached size limit.");
+
+        let not_err = resp_err.downcast_ref::<ContentTypeError>();
+        assert!(not_err.is_none());
+    }
+}