client-api: Add support for the Retry-After header

According to MSC4041 / Matrix 1.10

Co-authored-by: Jonas Platte <jplatte+git@posteo.de>

crates/ruma-client-api/CHANGELOG.md

@@ -16,6 +16,9 @@ Breaking changes:
 - `Error` is now non-exhaustive.
 - `ErrorKind::Forbidden` is now a non-exhaustive struct variant that can be
   constructed with `ErrorKind::forbidden()`.
+- The `retry_after_ms` field of `ErrorKind::LimitExceeded` was renamed to
+  `retry_after` and is now an `Option<RetryAfter>`, to add support for the
+  Retry-After header, according to MSC4041 / Matrix 1.10 
 
 Improvements:
 

crates/ruma-client-api/Cargo.toml

@@ -52,6 +52,7 @@ unstable-msc3983 = []
 as_variant = { workspace = true }
 assign = { workspace = true }
 bytes = "1.0.1"
+date_header = "1.0.5"
 http = { workspace = true }
 js_int = { workspace = true, features = ["serde"] }
 js_option = "0.1.1"
@@ -61,6 +62,8 @@ ruma-events = { workspace = true }
 serde = { workspace = true }
 serde_html_form = { workspace = true }
 serde_json = { workspace = true }
+thiserror = { workspace = true }
+web-time = { workspace = true }
 
 [dev-dependencies]
 assert_matches2 = { workspace = true }

crates/ruma-client-api/src/error.rs

@@ -1,6 +1,6 @@
 //! Errors that can be sent from the homeserver.
 
-use std::{collections::BTreeMap, fmt, sync::Arc, time::Duration};
+use std::{collections::BTreeMap, fmt, str::FromStr, sync::Arc};
 
 use as_variant::as_variant;
 use bytes::{BufMut, Bytes};
@@ -13,6 +13,8 @@ use ruma_common::{
 };
 use serde::{Deserialize, Serialize};
 use serde_json::{from_slice as from_json_slice, Value as JsonValue};
+use thiserror::Error;
+use web_time::{Duration, SystemTime, UNIX_EPOCH};
 
 use crate::PrivOwnedStr;
 
@@ -59,8 +61,8 @@ pub enum ErrorKind {
 
     /// M_LIMIT_EXCEEDED
     LimitExceeded {
-        /// How long a client should wait in milliseconds before they can try again.
-        retry_after_ms: Option<Duration>,
+        /// How long a client should wait before they can try again.
+        retry_after: Option<RetryAfter>,
     },
 
     /// M_UNKNOWN
@@ -350,19 +352,29 @@ impl EndpointError for Error {
 
         let body_bytes = &response.body().as_ref();
         let error_body: ErrorBody = match from_json_slice(body_bytes) {
-            Ok(StandardErrorBody { kind, message }) => {
-                #[cfg(feature = "unstable-msc2967")]
-                let kind = if let ErrorKind::Forbidden { .. } = kind {
-                    let authenticate = response
-                        .headers()
-                        .get(http::header::WWW_AUTHENTICATE)
-                        .and_then(|val| val.to_str().ok())
-                        .and_then(AuthenticateError::from_str);
+            Ok(StandardErrorBody { mut kind, message }) => {
+                let headers = response.headers();
 
-                    ErrorKind::Forbidden { authenticate }
-                } else {
-                    kind
-                };
+                match &mut kind {
+                    #[cfg(feature = "unstable-msc2967")]
+                    ErrorKind::Forbidden { authenticate } => {
+                        *authenticate = headers
+                            .get(http::header::WWW_AUTHENTICATE)
+                            .and_then(|val| val.to_str().ok())
+                            .and_then(AuthenticateError::from_str);
+                    }
+                    ErrorKind::LimitExceeded { retry_after } => {
+                        // The Retry-After header takes precedence over the retry_after_ms field in
+                        // the body.
+                        if let Some(retry_after_header) = headers
+                            .get(http::header::RETRY_AFTER)
+                            .and_then(RetryAfter::from_header_value)
+                        {
+                            *retry_after = Some(retry_after_header);
+                        }
+                    }
+                    _ => {}
+                }
 
                 ErrorBody::Standard { kind, message }
             }
@@ -406,20 +418,24 @@ impl OutgoingResponse for Error {
     fn try_into_http_response<T: Default + BufMut>(
         self,
     ) -> Result<http::Response<T>, IntoHttpError> {
-        let builder = http::Response::builder()
+        let mut builder = http::Response::builder()
             .header(http::header::CONTENT_TYPE, "application/json")
             .status(self.status_code);
 
-        #[cfg(feature = "unstable-msc2967")]
-        let builder = if let ErrorBody::Standard {
-            kind: ErrorKind::Forbidden { authenticate: Some(auth_error) },
-            ..
-        } = &self.body
-        {
-            builder.header(http::header::WWW_AUTHENTICATE, auth_error)
-        } else {
-            builder
-        };
+        #[allow(clippy::collapsible_match)]
+        if let ErrorBody::Standard { kind, .. } = &self.body {
+            match kind {
+                #[cfg(feature = "unstable-msc2967")]
+                ErrorKind::Forbidden { authenticate: Some(auth_error) } => {
+                    builder = builder.header(http::header::WWW_AUTHENTICATE, auth_error);
+                }
+                ErrorKind::LimitExceeded { retry_after: Some(retry_after) } => {
+                    let header_value = http::HeaderValue::try_from(retry_after)?;
+                    builder = builder.header(http::header::RETRY_AFTER, header_value);
+                }
+                _ => {}
+            }
+        }
 
         builder
             .body(match self.body {
@@ -532,6 +548,72 @@ impl TryFrom<&AuthenticateError> for http::HeaderValue {
     }
 }
 
+/// How long a client should wait before it tries again.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[allow(clippy::exhaustive_enums)]
+pub enum RetryAfter {
+    /// The client should wait for the given duration.
+    ///
+    /// This variant should be preferred for backwards compatibility, as it will also populate the
+    /// `retry_after_ms` field in the body of the response.
+    Delay(Duration),
+    /// The client should wait for the given date and time.
+    DateTime(SystemTime),
+}
+
+impl RetryAfter {
+    fn from_header_value(value: &http::HeaderValue) -> Option<Self> {
+        let bytes = value.as_bytes();
+
+        if bytes.iter().all(|b| b.is_ascii_digit()) {
+            // It should be a duration.
+            Some(Self::Delay(Duration::from_secs(u64::from_str(value.to_str().ok()?).ok()?)))
+        } else {
+            // It should be a date.
+            let ts = date_header::parse(bytes).ok()?;
+            Some(Self::DateTime(UNIX_EPOCH.checked_add(Duration::from_secs(ts))?))
+        }
+    }
+}
+
+impl TryFrom<&RetryAfter> for http::HeaderValue {
+    type Error = RetryAfterInvalidDateTime;
+
+    fn try_from(value: &RetryAfter) -> Result<Self, Self::Error> {
+        match value {
+            RetryAfter::Delay(duration) => Ok(duration.as_secs().into()),
+            RetryAfter::DateTime(time) => {
+                let mut buffer = [0; 29];
+                let duration =
+                    time.duration_since(UNIX_EPOCH).map_err(|_| RetryAfterInvalidDateTime)?;
+                date_header::format(duration.as_secs(), &mut buffer)
+                    .map_err(|_| RetryAfterInvalidDateTime)?;
+                let value = http::HeaderValue::from_bytes(&buffer)
+                    .expect("date_header should produce a valid header value");
+
+                Ok(value)
+            }
+        }
+    }
+}
+
+/// An error when converting a [`RetryAfter`] to a [`http::HeaderValue`].
+///
+/// Happens when the `DateTime` is too far in the past (before the Unix epoch) or the
+/// future (after the year 9999).
+#[derive(Debug, Error)]
+#[allow(clippy::exhaustive_structs)]
+#[error(
+    "Retry-After header serialization failed: the datetime is too far in the past or the future"
+)]
+pub struct RetryAfterInvalidDateTime;
+
+impl From<RetryAfterInvalidDateTime> for IntoHttpError {
+    fn from(_value: RetryAfterInvalidDateTime) -> Self {
+        IntoHttpError::RetryAfterInvalidDatetime
+    }
+}
+
 /// Extension trait for `FromHttpResponseError<ruma_client_api::Error>`.
 pub trait FromHttpResponseErrorExt {
     /// If `self` is a server error in the `errcode` + `error` format expected
@@ -548,9 +630,13 @@ impl FromHttpResponseErrorExt for FromHttpResponseError<Error> {
 #[cfg(test)]
 mod tests {
     use assert_matches2::assert_matches;
-    use serde_json::{from_value as from_json_value, json};
+    use ruma_common::api::{EndpointError, OutgoingResponse};
+    use serde_json::{
+        from_slice as from_json_slice, from_value as from_json_value, json, Value as JsonValue,
+    };
+    use web_time::{Duration, UNIX_EPOCH};
 
-    use super::{ErrorKind, StandardErrorBody};
+    use super::{Error, ErrorBody, ErrorKind, RetryAfter, StandardErrorBody};
 
     #[test]
     fn deserialize_forbidden() {
@@ -615,9 +701,7 @@ mod tests {
     #[cfg(feature = "unstable-msc2967")]
     #[test]
     fn deserialize_insufficient_scope() {
-        use ruma_common::api::EndpointError;
-
-        use super::{AuthenticateError, Error, ErrorBody};
+        use super::AuthenticateError;
 
         let response = http::Response::builder()
             .header(
@@ -642,4 +726,223 @@ mod tests {
         assert_matches!(authenticate, Some(AuthenticateError::InsufficientScope { scope }));
         assert_eq!(scope, "something_privileged");
     }
+
+    #[test]
+    fn deserialize_limit_exceeded_no_retry_after() {
+        let response = http::Response::builder()
+            .status(http::StatusCode::TOO_MANY_REQUESTS)
+            .body(
+                serde_json::to_string(&json!({
+                    "errcode": "M_LIMIT_EXCEEDED",
+                    "error": "Too many requests",
+                }))
+                .unwrap(),
+            )
+            .unwrap();
+        let error = Error::from_http_response(response);
+
+        assert_eq!(error.status_code, http::StatusCode::TOO_MANY_REQUESTS);
+        assert_matches!(
+            error.body,
+            ErrorBody::Standard { kind: ErrorKind::LimitExceeded { retry_after: None }, message }
+        );
+        assert_eq!(message, "Too many requests");
+    }
+
+    #[test]
+    fn deserialize_limit_exceeded_retry_after_body() {
+        let response = http::Response::builder()
+            .status(http::StatusCode::TOO_MANY_REQUESTS)
+            .body(
+                serde_json::to_string(&json!({
+                    "errcode": "M_LIMIT_EXCEEDED",
+                    "error": "Too many requests",
+                    "retry_after_ms": 2000,
+                }))
+                .unwrap(),
+            )
+            .unwrap();
+        let error = Error::from_http_response(response);
+
+        assert_eq!(error.status_code, http::StatusCode::TOO_MANY_REQUESTS);
+        assert_matches!(
+            error.body,
+            ErrorBody::Standard {
+                kind: ErrorKind::LimitExceeded { retry_after: Some(retry_after) },
+                message
+            }
+        );
+        assert_matches!(retry_after, RetryAfter::Delay(delay));
+        assert_eq!(delay.as_millis(), 2000);
+        assert_eq!(message, "Too many requests");
+    }
+
+    #[test]
+    fn deserialize_limit_exceeded_retry_after_header_delay() {
+        let response = http::Response::builder()
+            .status(http::StatusCode::TOO_MANY_REQUESTS)
+            .header(http::header::RETRY_AFTER, "2")
+            .body(
+                serde_json::to_string(&json!({
+                    "errcode": "M_LIMIT_EXCEEDED",
+                    "error": "Too many requests",
+                }))
+                .unwrap(),
+            )
+            .unwrap();
+        let error = Error::from_http_response(response);
+
+        assert_eq!(error.status_code, http::StatusCode::TOO_MANY_REQUESTS);
+        assert_matches!(
+            error.body,
+            ErrorBody::Standard {
+                kind: ErrorKind::LimitExceeded { retry_after: Some(retry_after) },
+                message
+            }
+        );
+        assert_matches!(retry_after, RetryAfter::Delay(delay));
+        assert_eq!(delay.as_millis(), 2000);
+        assert_eq!(message, "Too many requests");
+    }
+
+    #[test]
+    fn deserialize_limit_exceeded_retry_after_header_datetime() {
+        let response = http::Response::builder()
+            .status(http::StatusCode::TOO_MANY_REQUESTS)
+            .header(http::header::RETRY_AFTER, "Fri, 15 May 2015 15:34:21 GMT")
+            .body(
+                serde_json::to_string(&json!({
+                    "errcode": "M_LIMIT_EXCEEDED",
+                    "error": "Too many requests",
+                }))
+                .unwrap(),
+            )
+            .unwrap();
+        let error = Error::from_http_response(response);
+
+        assert_eq!(error.status_code, http::StatusCode::TOO_MANY_REQUESTS);
+        assert_matches!(
+            error.body,
+            ErrorBody::Standard {
+                kind: ErrorKind::LimitExceeded { retry_after: Some(retry_after) },
+                message
+            }
+        );
+        assert_matches!(retry_after, RetryAfter::DateTime(time));
+        assert_eq!(time.duration_since(UNIX_EPOCH).unwrap().as_secs(), 1_431_704_061);
+        assert_eq!(message, "Too many requests");
+    }
+
+    #[test]
+    fn deserialize_limit_exceeded_retry_after_header_over_body() {
+        let response = http::Response::builder()
+            .status(http::StatusCode::TOO_MANY_REQUESTS)
+            .header(http::header::RETRY_AFTER, "2")
+            .body(
+                serde_json::to_string(&json!({
+                    "errcode": "M_LIMIT_EXCEEDED",
+                    "error": "Too many requests",
+                    "retry_after_ms": 3000,
+                }))
+                .unwrap(),
+            )
+            .unwrap();
+        let error = Error::from_http_response(response);
+
+        assert_eq!(error.status_code, http::StatusCode::TOO_MANY_REQUESTS);
+        assert_matches!(
+            error.body,
+            ErrorBody::Standard {
+                kind: ErrorKind::LimitExceeded { retry_after: Some(retry_after) },
+                message
+            }
+        );
+        assert_matches!(retry_after, RetryAfter::Delay(delay));
+        assert_eq!(delay.as_millis(), 2000);
+        assert_eq!(message, "Too many requests");
+    }
+
+    #[test]
+    fn serialize_limit_exceeded_retry_after_none() {
+        let error = Error::new(
+            http::StatusCode::TOO_MANY_REQUESTS,
+            ErrorBody::Standard {
+                kind: ErrorKind::LimitExceeded { retry_after: None },
+                message: "Too many requests".to_owned(),
+            },
+        );
+
+        let response = error.try_into_http_response::<Vec<u8>>().unwrap();
+
+        assert_eq!(response.status(), http::StatusCode::TOO_MANY_REQUESTS);
+        assert_eq!(response.headers().get(http::header::RETRY_AFTER), None);
+
+        let json_body: JsonValue = from_json_slice(response.body()).unwrap();
+        assert_eq!(
+            json_body,
+            json!({
+                "errcode": "M_LIMIT_EXCEEDED",
+                "error": "Too many requests",
+            })
+        );
+    }
+
+    #[test]
+    fn serialize_limit_exceeded_retry_after_delay() {
+        let error = Error::new(
+            http::StatusCode::TOO_MANY_REQUESTS,
+            ErrorBody::Standard {
+                kind: ErrorKind::LimitExceeded {
+                    retry_after: Some(RetryAfter::Delay(Duration::from_secs(3))),
+                },
+                message: "Too many requests".to_owned(),
+            },
+        );
+
+        let response = error.try_into_http_response::<Vec<u8>>().unwrap();
+
+        assert_eq!(response.status(), http::StatusCode::TOO_MANY_REQUESTS);
+        let retry_after_header = response.headers().get(http::header::RETRY_AFTER).unwrap();
+        assert_eq!(retry_after_header.to_str().unwrap(), "3");
+
+        let json_body: JsonValue = from_json_slice(response.body()).unwrap();
+        assert_eq!(
+            json_body,
+            json!({
+                "errcode": "M_LIMIT_EXCEEDED",
+                "error": "Too many requests",
+                "retry_after_ms": 3000,
+            })
+        );
+    }
+
+    #[test]
+    fn serialize_limit_exceeded_retry_after_datetime() {
+        let error = Error::new(
+            http::StatusCode::TOO_MANY_REQUESTS,
+            ErrorBody::Standard {
+                kind: ErrorKind::LimitExceeded {
+                    retry_after: Some(RetryAfter::DateTime(
+                        UNIX_EPOCH + Duration::from_secs(1_431_704_061),
+                    )),
+                },
+                message: "Too many requests".to_owned(),
+            },
+        );
+
+        let response = error.try_into_http_response::<Vec<u8>>().unwrap();
+
+        assert_eq!(response.status(), http::StatusCode::TOO_MANY_REQUESTS);
+        let retry_after_header = response.headers().get(http::header::RETRY_AFTER).unwrap();
+        assert_eq!(retry_after_header.to_str().unwrap(), "Fri, 15 May 2015 15:34:21 GMT");
+
+        let json_body: JsonValue = from_json_slice(response.body()).unwrap();
+        assert_eq!(
+            json_body,
+            json!({
+                "errcode": "M_LIMIT_EXCEEDED",
+                "error": "Too many requests",
+            })
+        );
+    }
 }

crates/ruma-client-api/src/error/kind_serde.rs

@@ -13,7 +13,7 @@ use serde::{
 };
 use serde_json::from_value as from_json_value;
 
-use super::{ErrorKind, Extra};
+use super::{ErrorKind, Extra, RetryAfter};
 use crate::PrivOwnedStr;
 
 enum Field<'de> {
@@ -178,12 +178,13 @@ impl<'de> Visitor<'de> for ErrorKindVisitor {
             ErrCode::NotJson => ErrorKind::NotJson,
             ErrCode::NotFound => ErrorKind::NotFound,
             ErrCode::LimitExceeded => ErrorKind::LimitExceeded {
-                retry_after_ms: retry_after_ms
+                retry_after: retry_after_ms
                     .map(from_json_value::<UInt>)
                     .transpose()
                     .map_err(de::Error::custom)?
                     .map(Into::into)
-                    .map(Duration::from_millis),
+                    .map(Duration::from_millis)
+                    .map(RetryAfter::Delay),
             },
             ErrCode::Unknown => ErrorKind::Unknown,
             ErrCode::Unrecognized => ErrorKind::Unrecognized,
@@ -328,7 +329,7 @@ impl Serialize for ErrorKind {
             Self::UnknownToken { soft_logout: true } => {
                 st.serialize_entry("soft_logout", &true)?;
             }
-            Self::LimitExceeded { retry_after_ms: Some(duration) } => {
+            Self::LimitExceeded { retry_after: Some(RetryAfter::Delay(duration)) } => {
                 st.serialize_entry(
                     "retry_after_ms",
                     &UInt::try_from(duration.as_millis()).map_err(ser::Error::custom)?,

crates/ruma-common/src/api/error.rs

@@ -129,6 +129,13 @@ pub enum IntoHttpError {
     #[error("header serialization failed: {0}")]
     Header(#[from] http::header::InvalidHeaderValue),
 
+    /// Retry-After header serialization failed because the datetime provided is after the year
+    /// 9999.
+    #[error(
+        "Retry-After header serialization failed: the year of the datetime is bigger than 9999"
+    )]
+    RetryAfterInvalidDatetime,
+
     /// HTTP request construction failed.
     #[error("HTTP request construction failed: {0}")]
     Http(#[from] http::Error),