Use anyhow more idiomatically (#31052)

https://github.com/zed-industries/zed/issues/30972 brought up another
case where our context is not enough to track the actual source of the
issue: we get a general top-level error without inner error.

The reason for this was `.ok_or_else(|| anyhow!("failed to read HEAD
SHA"))?; ` on the top level.

The PR finally reworks the way we use anyhow to reduce such issues (or
at least make it simpler to bubble them up later in a fix).
On top of that, uses a few more anyhow methods for better readability.

* `.ok_or_else(|| anyhow!("..."))`, `map_err` and other similar error
conversion/option reporting cases are replaced with `context` and
`with_context` calls
* in addition to that, various `anyhow!("failed to do ...")` are
stripped with `.context("Doing ...")` messages instead to remove the
parasitic `failed to` text
* `anyhow::ensure!` is used instead of `if ... { return Err(...); }`
calls
* `anyhow::bail!` is used instead of `return Err(anyhow!(...));`

Release Notes:

- N/A

crates/rpc/src/conn.rs

@@ -4,12 +4,8 @@ use futures::{SinkExt as _, StreamExt as _};
 pub struct Connection {
     pub(crate) tx:
         Box<dyn 'static + Send + Unpin + futures::Sink<WebSocketMessage, Error = anyhow::Error>>,
-    pub(crate) rx: Box<
-        dyn 'static
-            + Send
-            + Unpin
-            + futures::Stream<Item = Result<WebSocketMessage, anyhow::Error>>,
-    >,
+    pub(crate) rx:
+        Box<dyn 'static + Send + Unpin + futures::Stream<Item = anyhow::Result<WebSocketMessage>>>,
 }
 
 impl Connection {
@@ -19,7 +15,7 @@ impl Connection {
             + Send
             + Unpin
             + futures::Sink<WebSocketMessage, Error = anyhow::Error>
-            + futures::Stream<Item = Result<WebSocketMessage, anyhow::Error>>,
+            + futures::Stream<Item = anyhow::Result<WebSocketMessage>>,
     {
         let (tx, rx) = stream.split();
         Self {
@@ -28,7 +24,7 @@ impl Connection {
         }
     }
 
-    pub async fn send(&mut self, message: WebSocketMessage) -> Result<(), anyhow::Error> {
+    pub async fn send(&mut self, message: WebSocketMessage) -> anyhow::Result<()> {
         self.tx.send(message).await
     }
 
@@ -56,7 +52,7 @@ impl Connection {
             executor: gpui::BackgroundExecutor,
         ) -> (
             Box<dyn Send + Unpin + futures::Sink<WebSocketMessage, Error = anyhow::Error>>,
-            Box<dyn Send + Unpin + futures::Stream<Item = Result<WebSocketMessage, anyhow::Error>>>,
+            Box<dyn Send + Unpin + futures::Stream<Item = anyhow::Result<WebSocketMessage>>>,
         ) {
             use anyhow::anyhow;
             use futures::channel::mpsc;

crates/rpc/src/message_stream.rs

@@ -2,7 +2,6 @@
 
 pub use ::proto::*;
 
-use anyhow::anyhow;
 use async_tungstenite::tungstenite::Message as WebSocketMessage;
 use futures::{SinkExt as _, StreamExt as _};
 use proto::Message as _;
@@ -40,7 +39,7 @@ impl<S> MessageStream<S>
 where
     S: futures::Sink<WebSocketMessage, Error = anyhow::Error> + Unpin,
 {
-    pub async fn write(&mut self, message: Message) -> Result<(), anyhow::Error> {
+    pub async fn write(&mut self, message: Message) -> anyhow::Result<()> {
         #[cfg(any(test, feature = "test-support"))]
         const COMPRESSION_LEVEL: i32 = -7;
 
@@ -81,9 +80,9 @@ where
 
 impl<S> MessageStream<S>
 where
-    S: futures::Stream<Item = Result<WebSocketMessage, anyhow::Error>> + Unpin,
+    S: futures::Stream<Item = anyhow::Result<WebSocketMessage>> + Unpin,
 {
-    pub async fn read(&mut self) -> Result<(Message, Instant), anyhow::Error> {
+    pub async fn read(&mut self) -> anyhow::Result<(Message, Instant)> {
         while let Some(bytes) = self.stream.next().await {
             let received_at = Instant::now();
             match bytes? {
@@ -102,7 +101,7 @@ where
                 _ => {}
             }
         }
-        Err(anyhow!("connection closed"))
+        anyhow::bail!("connection closed");
     }
 }
 
@@ -113,7 +112,7 @@ mod tests {
     #[gpui::test]
     async fn test_buffer_size() {
         let (tx, rx) = futures::channel::mpsc::unbounded();
-        let mut sink = MessageStream::new(tx.sink_map_err(|_| anyhow!("")));
+        let mut sink = MessageStream::new(tx.sink_map_err(|_| anyhow::anyhow!("")));
         sink.write(Message::Envelope(Envelope {
             payload: Some(envelope::Payload::UpdateWorktree(UpdateWorktree {
                 root_name: "abcdefg".repeat(10),

crates/rpc/src/peer.rs

@@ -197,7 +197,7 @@ impl Peer {
                                     }
                                     _ = create_timer(WRITE_TIMEOUT).fuse() => {
                                         tracing::trace!(%connection_id, "outgoing rpc message: writing timed out");
-                                        Err(anyhow!("timed out writing message"))?;
+                                        anyhow::bail!("timed out writing message");
                                     }
                                 }
                             }
@@ -217,7 +217,7 @@ impl Peer {
                                 }
                                 _ = create_timer(WRITE_TIMEOUT).fuse() => {
                                     tracing::trace!(%connection_id, "keepalive interval: pinging timed out");
-                                    Err(anyhow!("timed out sending keepalive"))?;
+                                    anyhow::bail!("timed out sending keepalive");
                                 }
                             }
                         }
@@ -240,7 +240,7 @@ impl Peer {
                                     },
                                     _ = create_timer(WRITE_TIMEOUT).fuse() => {
                                         tracing::trace!(%connection_id, "incoming rpc message: processing timed out");
-                                        Err(anyhow!("timed out processing incoming message"))?
+                                        anyhow::bail!("timed out processing incoming message");
                                     }
                                 }
                             }
@@ -248,7 +248,7 @@ impl Peer {
                         },
                         _ = receive_timeout => {
                             tracing::trace!(%connection_id, "receive timeout: delay between messages too long");
-                            Err(anyhow!("delay between messages too long"))?
+                            anyhow::bail!("delay between messages too long");
                         }
                     }
                 }
@@ -441,7 +441,7 @@ impl Peer {
                 sender_id: receiver_id.into(),
                 original_sender_id: response.original_sender_id,
                 payload: T::Response::from_envelope(response)
-                    .ok_or_else(|| anyhow!("received response of the wrong type"))?,
+                    .context("received response of the wrong type")?,
                 received_at,
             })
         }
@@ -465,18 +465,17 @@ impl Peer {
                 .response_channels
                 .lock()
                 .as_mut()
-                .ok_or_else(|| anyhow!("connection was closed"))?
+                .context("connection was closed")?
                 .insert(envelope.id, tx);
             connection
                 .outgoing_tx
                 .unbounded_send(Message::Envelope(envelope))
-                .map_err(|_| anyhow!("connection was closed"))?;
+                .context("connection was closed")?;
             Ok(())
         });
         async move {
             send?;
-            let (response, received_at, _barrier) =
-                rx.await.map_err(|_| anyhow!("connection was closed"))?;
+            let (response, received_at, _barrier) = rx.await.context("connection was closed")?;
             if let Some(proto::envelope::Payload::Error(error)) = &response.payload {
                 return Err(RpcError::from_proto(error, type_name));
             }
@@ -496,14 +495,14 @@ impl Peer {
             stream_response_channels
                 .lock()
                 .as_mut()
-                .ok_or_else(|| anyhow!("connection was closed"))?
+                .context("connection was closed")?
                 .insert(message_id, tx);
             connection
                 .outgoing_tx
                 .unbounded_send(Message::Envelope(
                     request.into_envelope(message_id, None, None),
                 ))
-                .map_err(|_| anyhow!("connection was closed"))?;
+                .context("connection was closed")?;
             Ok((message_id, stream_response_channels))
         });
 
@@ -530,7 +529,7 @@ impl Peer {
                         } else {
                             Some(
                                 T::Response::from_envelope(response)
-                                    .ok_or_else(|| anyhow!("received response of the wrong type")),
+                                    .context("received response of the wrong type"),
                             )
                         }
                     }
@@ -662,7 +661,7 @@ impl Peer {
         let connections = self.connections.read();
         let connection = connections
             .get(&connection_id)
-            .ok_or_else(|| anyhow!("no such connection: {}", connection_id))?;
+            .with_context(|| format!("no such connection: {connection_id}"))?;
         Ok(connection.clone())
     }
 }

crates/rpc/src/proto_client.rs

@@ -1,4 +1,4 @@
-use anyhow::anyhow;
+use anyhow::Context;
 use collections::HashMap;
 use futures::{
     Future, FutureExt as _,
@@ -190,7 +190,7 @@ impl AnyProtoClient {
         let response = self.0.request(envelope, T::NAME);
         async move {
             T::Response::from_envelope(response.await?)
-                .ok_or_else(|| anyhow!("received response of the wrong type"))
+                .context("received response of the wrong type")
         }
     }