spawn errors: Fix arti-client, tor-chanmgr, tor-circmgr

Provide an enum variant to contain the SpawnError and a From impl.

We use `#[from]` here because it doesn't really make sense to attach
any context, as it's not likely to be very relevant.

crates/arti-client/src/err.rs

@@ -1,5 +1,8 @@
 //! Declare tor client specific errors.
 
+use std::sync::Arc;
+
+use futures::task::SpawnError;
 use thiserror::Error;
 use tor_rtcompat::TimeoutError;
 
@@ -54,6 +57,10 @@ pub enum Error {
     /// Unable to change configuration.
     #[error("Reconfiguration failed: {0}")]
     Reconfigure(#[from] tor_config::ReconfigureError),
+
+    /// Unable to spawn task
+    #[error("unable to spawn task")]
+    Spawn(#[from] Arc<SpawnError>),
 }
 
 impl From<TimeoutError> for Error {
@@ -62,8 +69,8 @@ impl From<TimeoutError> for Error {
     }
 }
 
-impl From<futures::task::SpawnError> for Error {
-    fn from(_: futures::task::SpawnError) -> Error {
-        Error::Internal("Couldn't spawn channel reactor")
+impl From<SpawnError> for Error {
+    fn from(e: SpawnError) -> Error {
+        Arc::new(e).into()
     }
 }

crates/tor-chanmgr/src/err.rs

@@ -1,6 +1,8 @@
 //! Declare error types for tor-chanmgr
 
 use std::sync::Arc;
+
+use futures::task::SpawnError;
 use thiserror::Error;
 
 /// An error returned by a channel manager.
@@ -27,14 +29,18 @@ pub enum Error {
     #[error("I/O error while opening a channel: {0}")]
     Io(#[source] Arc<std::io::Error>),
 
+    /// Unable to spawn task
+    #[error("unable to spawn task")]
+    Spawn(#[from] Arc<SpawnError>),
+
     /// An internal error of some kind that should never occur.
     #[error("Internal error: {0}")]
     Internal(&'static str),
 }
 
-impl From<futures::task::SpawnError> for Error {
-    fn from(_: futures::task::SpawnError) -> Error {
-        Error::Internal("Couldn't spawn channel reactor")
+impl From<SpawnError> for Error {
+    fn from(e: SpawnError) -> Error {
+        Arc::new(e).into()
     }
 }
 

crates/tor-circmgr/src/err.rs

@@ -1,5 +1,8 @@
 //! Declare an error type for tor-circmgr
 
+use std::sync::Arc;
+
+use futures::task::SpawnError;
 use retry_error::RetryError;
 use thiserror::Error;
 
@@ -77,6 +80,10 @@ pub enum Error {
     /// We have an expired consensus
     #[error("Consensus is expired")]
     ExpiredConsensus,
+
+    /// Unable to spawn task
+    #[error("unable to spawn task")]
+    Spawn(#[from] Arc<SpawnError>),
 }
 
 impl From<futures::channel::oneshot::Canceled> for Error {
@@ -85,9 +92,9 @@ impl From<futures::channel::oneshot::Canceled> for Error {
     }
 }
 
-impl From<futures::task::SpawnError> for Error {
-    fn from(_: futures::task::SpawnError) -> Error {
-        Error::Internal("Unable to spawn new task in executor.".into())
+impl From<SpawnError> for Error {
+    fn from(e: SpawnError) -> Error {
+        Arc::new(e).into()
     }
 }