Try to send typed errors back and forth

TEMP

TEMP

First pass of structured errors

Improved error handling for channel joining failures

crates/rpc/proto/zed.proto

@@ -197,6 +197,18 @@ message Ack {}
 
 message Error {
     string message = 1;
+    ErrorCode code = 2;
+    repeated string tags = 3;
+}
+
+enum ErrorCode {
+    Internal = 0;
+    NoSuchChannel = 1;
+    Disconnected = 2;
+    SignedOut = 3;
+    UpgradeRequired = 4;
+    Forbidden = 5;
+    WrongReleaseChannel = 6;
 }
 
 message Test {

crates/rpc/src/error.rs

@@ -0,0 +1,223 @@
+/// Some helpers for structured error handling.
+///
+/// The helpers defined here allow you to pass type-safe error codes from
+/// the collab server to the client; and provide a mechanism for additional
+/// structured data alongside the message.
+///
+/// When returning an error, it can be as simple as:
+///
+/// `return Err(Error::Forbidden.into())`
+///
+/// If you'd like to log more context, you can set a message. These messages
+/// show up in our logs, but are not shown visibly to users.
+///
+/// `return Err(Error::Forbidden.message("not an admin").into())`
+///
+/// If you'd like to provide enough context that the UI can render a good error
+/// message (or would be helpful to see in a structured format in the logs), you
+/// can use .with_tag():
+///
+/// `return Err(Error::WrongReleaseChannel.with_tag("required", "stable").into())`
+///
+/// When handling an error you can use .error_code() to match which error it was
+/// and .error_tag() to read any tags.
+///
+/// ```
+/// match err.error_code() {
+///   ErrorCode::Forbidden => alert("I'm sorry I can't do that.")
+///   ErrorCode::WrongReleaseChannel =>
+///     alert(format!("You need to be on the {} release channel.", err.error_tag("required").unwrap()))
+///   ErrorCode::Internal => alert("Sorry, something went wrong")
+/// }
+/// ```
+///
+use crate::proto;
+pub use proto::ErrorCode;
+
+/// ErrorCodeExt provides some helpers for structured error handling.
+///
+/// The primary implementation is on the proto::ErrorCode to easily convert
+/// that into an anyhow::Error, which we use pervasively.
+///
+/// The RPCError struct provides support for further metadata if needed.
+pub trait ErrorCodeExt {
+    /// Return an anyhow::Error containing this.
+    /// (useful in places where .into() doesn't have enough type information)
+    fn anyhow(self) -> anyhow::Error;
+
+    /// Add a message to the error (by default the error code is used)
+    fn message(self, msg: String) -> RPCError;
+
+    /// Add a tag to the error. Tags are key value pairs that can be used
+    /// to send semi-structured data along with the error.
+    fn with_tag(self, k: &str, v: &str) -> RPCError;
+}
+
+impl ErrorCodeExt for proto::ErrorCode {
+    fn anyhow(self) -> anyhow::Error {
+        self.into()
+    }
+
+    fn message(self, msg: String) -> RPCError {
+        let err: RPCError = self.into();
+        err.message(msg)
+    }
+
+    fn with_tag(self, k: &str, v: &str) -> RPCError {
+        let err: RPCError = self.into();
+        err.with_tag(k, v)
+    }
+}
+
+/// ErrorExt provides helpers for structured error handling.
+///
+/// The primary implementation is on the anyhow::Error, which is
+/// what we use throughout our codebase. Though under the hood this
+pub trait ErrorExt {
+    /// error_code() returns the ErrorCode (or ErrorCode::Internal if there is none)
+    fn error_code(&self) -> proto::ErrorCode;
+    /// error_tag() returns the value of the tag with the given key, if any.
+    fn error_tag(&self, k: &str) -> Option<&str>;
+    /// to_proto() convers the error into a proto::Error
+    fn to_proto(&self) -> proto::Error;
+}
+
+impl ErrorExt for anyhow::Error {
+    fn error_code(&self) -> proto::ErrorCode {
+        if let Some(rpc_error) = self.downcast_ref::<RPCError>() {
+            rpc_error.code
+        } else {
+            proto::ErrorCode::Internal
+        }
+    }
+
+    fn error_tag(&self, k: &str) -> Option<&str> {
+        if let Some(rpc_error) = self.downcast_ref::<RPCError>() {
+            rpc_error.error_tag(k)
+        } else {
+            None
+        }
+    }
+
+    fn to_proto(&self) -> proto::Error {
+        if let Some(rpc_error) = self.downcast_ref::<RPCError>() {
+            rpc_error.to_proto()
+        } else {
+            ErrorCode::Internal.message(format!("{}", self)).to_proto()
+        }
+    }
+}
+
+impl From<proto::ErrorCode> for anyhow::Error {
+    fn from(value: proto::ErrorCode) -> Self {
+        RPCError {
+            request: None,
+            code: value,
+            msg: format!("{:?}", value).to_string(),
+            tags: Default::default(),
+        }
+        .into()
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct RPCError {
+    request: Option<String>,
+    msg: String,
+    code: proto::ErrorCode,
+    tags: Vec<String>,
+}
+
+/// RPCError is a structured error type that is returned by the collab server.
+/// In addition to a message, it lets you set a specific ErrorCode, and attach
+/// small amounts of metadata to help the client handle the error appropriately.
+///
+/// This struct is not typically used directly, as we pass anyhow::Error around
+/// in the app; however it is useful for chaining .message() and .with_tag() on
+/// ErrorCode.
+impl RPCError {
+    /// from_proto converts a proto::Error into an anyhow::Error containing
+    /// an RPCError.
+    pub fn from_proto(error: &proto::Error, request: &str) -> anyhow::Error {
+        RPCError {
+            request: Some(request.to_string()),
+            code: error.code(),
+            msg: error.message.clone(),
+            tags: error.tags.clone(),
+        }
+        .into()
+    }
+}
+
+impl ErrorCodeExt for RPCError {
+    fn message(mut self, msg: String) -> RPCError {
+        self.msg = msg;
+        self
+    }
+
+    fn with_tag(mut self, k: &str, v: &str) -> RPCError {
+        self.tags.push(format!("{}={}", k, v));
+        self
+    }
+
+    fn anyhow(self) -> anyhow::Error {
+        self.into()
+    }
+}
+
+impl ErrorExt for RPCError {
+    fn error_tag(&self, k: &str) -> Option<&str> {
+        for tag in &self.tags {
+            let mut parts = tag.split('=');
+            if let Some(key) = parts.next() {
+                if key == k {
+                    return parts.next();
+                }
+            }
+        }
+        None
+    }
+
+    fn error_code(&self) -> proto::ErrorCode {
+        self.code
+    }
+
+    fn to_proto(&self) -> proto::Error {
+        proto::Error {
+            code: self.code as i32,
+            message: self.msg.clone(),
+            tags: self.tags.clone(),
+        }
+    }
+}
+
+impl std::error::Error for RPCError {
+    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+        None
+    }
+}
+
+impl std::fmt::Display for RPCError {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        if let Some(request) = &self.request {
+            write!(f, "RPC request {} failed: {}", request, self.msg)?
+        } else {
+            write!(f, "{}", self.msg)?
+        }
+        for tag in &self.tags {
+            write!(f, " {}", tag)?
+        }
+        Ok(())
+    }
+}
+
+impl From<proto::ErrorCode> for RPCError {
+    fn from(code: proto::ErrorCode) -> Self {
+        RPCError {
+            request: None,
+            code,
+            msg: format!("{:?}", code).to_string(),
+            tags: Default::default(),
+        }
+    }
+}

crates/rpc/src/peer.rs

@@ -1,3 +1,5 @@
+use crate::{ErrorCode, ErrorCodeExt, ErrorExt, RPCError};
+
 use super::{
     proto::{self, AnyTypedEnvelope, EnvelopedMessage, MessageStream, PeerId, RequestMessage},
     Connection,
@@ -423,11 +425,7 @@ impl Peer {
             let (response, _barrier) = rx.await.map_err(|_| anyhow!("connection was closed"))?;
 
             if let Some(proto::envelope::Payload::Error(error)) = &response.payload {
-                Err(anyhow!(
-                    "RPC request {} failed - {}",
-                    T::NAME,
-                    error.message
-                ))
+                Err(RPCError::from_proto(&error, T::NAME))
             } else {
                 Ok(TypedEnvelope {
                     message_id: response.id,
@@ -516,9 +514,12 @@ impl Peer {
         envelope: Box<dyn AnyTypedEnvelope>,
     ) -> Result<()> {
         let connection = self.connection_state(envelope.sender_id())?;
-        let response = proto::Error {
-            message: format!("message {} was not handled", envelope.payload_type_name()),
-        };
+        let response = ErrorCode::Internal
+            .message(format!(
+                "message {} was not handled",
+                envelope.payload_type_name()
+            ))
+            .to_proto();
         let message_id = connection
             .next_message_id
             .fetch_add(1, atomic::Ordering::SeqCst);
@@ -692,17 +693,17 @@ mod tests {
                 server
                     .send(
                         server_to_client_conn_id,
-                        proto::Error {
-                            message: "message 1".to_string(),
-                        },
+                        ErrorCode::Internal
+                            .message("message 1".to_string())
+                            .to_proto(),
                     )
                     .unwrap();
                 server
                     .send(
                         server_to_client_conn_id,
-                        proto::Error {
-                            message: "message 2".to_string(),
-                        },
+                        ErrorCode::Internal
+                            .message("message 2".to_string())
+                            .to_proto(),
                     )
                     .unwrap();
                 server.respond(request.receipt(), proto::Ack {}).unwrap();
@@ -797,17 +798,17 @@ mod tests {
                 server
                     .send(
                         server_to_client_conn_id,
-                        proto::Error {
-                            message: "message 1".to_string(),
-                        },
+                        ErrorCode::Internal
+                            .message("message 1".to_string())
+                            .to_proto(),
                     )
                     .unwrap();
                 server
                     .send(
                         server_to_client_conn_id,
-                        proto::Error {
-                            message: "message 2".to_string(),
-                        },
+                        ErrorCode::Internal
+                            .message("message 2".to_string())
+                            .to_proto(),
                     )
                     .unwrap();
                 server.respond(request1.receipt(), proto::Ack {}).unwrap();

crates/rpc/src/rpc.rs

@@ -1,10 +1,12 @@
 pub mod auth;
 mod conn;
+mod error;
 mod notification;
 mod peer;
 pub mod proto;
 
 pub use conn::Connection;
+pub use error::*;
 pub use notification::*;
 pub use peer::*;
 mod macros;