Merge branch 'error-chain'

1 files changed, 24 insertions, 53 deletions

diff --git a/src/process/monitor.rs b/src/process/monitor.rs
index e8d32a7973..8caac5cc79 100644
--- a/src/process/monitor.rs
+++ b/src/process/monitor.rs
@@ -1,11 +1,27 @@
-use std::error::Error;
-use std::fmt;
 use std::io;
 use std::process::{ChildStdout, ChildStderr};
 use std::sync::{Arc, Mutex};
 use std::thread;
 
 
+error_chain! {
+    errors {
+        /// The transition could not be made because the state machine was not in a state that
+        /// could transition to the desired state.
+        InvalidState {
+            description("Invalid state for desired transition")
+        }
+        /// Error representing a failure in spawning the child process
+        Spawn {
+            description("Unable to spawn child process")
+        }
+        /// Error representing a failure in sending a kill signal to the child process
+        Kill {
+            description("Unable to send kill signal to process")
+        }
+    }
+}
+
 /// Trait for objects that represent child processes that `ChildMonitor` can monitor
 pub trait MonitoredChild: Clone + Send + 'static {
     /// Waits for the child to exit completely, returning if the child exited cleanly or not.
@@ -31,49 +47,6 @@ pub trait ChildSpawner: Send + 'static {
 }
 
 
-/// Type alias for results of transitions in the `ChildMonitor` state machine.
-pub type TransitionResult<T> = Result<T, TransitionError>;
-
-/// Error type for transitions in the `ChildMonitor` state machine.
-#[derive(Debug)]
-pub enum TransitionError {
-    /// The transition could not be made because the state machine was not in a state that could
-    /// transition to the desired state.
-    InvalidState,
-
-    /// The transition failed because of an `io::Error`.
-    IoError(io::Error),
-}
-
-impl From<io::Error> for TransitionError {
-    fn from(error: io::Error) -> Self {
-        TransitionError::IoError(error)
-    }
-}
-
-impl fmt::Display for TransitionError {
-    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
-        fmt.write_str(self.description())
-    }
-}
-
-impl Error for TransitionError {
-    fn description(&self) -> &str {
-        match *self {
-            TransitionError::InvalidState => "Invalid state for desired transition",
-            TransitionError::IoError(..) => "Transition failed due to IO error",
-        }
-    }
-
-    fn cause(&self) -> Option<&Error> {
-        match *self {
-            TransitionError::IoError(ref e) => Some(e),
-            _ => None,
-        }
-    }
-}
-
-
 enum State<C: MonitoredChild> {
     Stopped,
     Running(RunningState<C>),
@@ -104,14 +77,12 @@ impl<S: ChildSpawner> ChildMonitor<S> {
 
     /// Starts the child process and begins to monitor it. `listener` will be called as soon as the
     /// child process exits.
-    pub fn start<L>(&mut self,
-                    listener: L)
-                    -> TransitionResult<(Option<ChildStdout>, Option<ChildStderr>)>
+    pub fn start<L>(&mut self, listener: L) -> Result<(Option<ChildStdout>, Option<ChildStderr>)>
         where L: FnMut(bool) + Send + 'static
     {
         let mut state_lock = self.state.lock().unwrap();
         if let State::Stopped = *state_lock {
-            let mut child = self.spawner.spawn()?;
+            let mut child = self.spawner.spawn().chain_err(|| ErrorKind::Spawn)?;
             let io = (child.stdout(), child.stderr());
             let thread_handle = self.spawn_monitor(child.clone(), listener);
             *state_lock = State::Running(RunningState {
@@ -120,7 +91,7 @@ impl<S: ChildSpawner> ChildMonitor<S> {
             });
             Ok(io)
         } else {
-            Err(TransitionError::InvalidState)
+            Err(ErrorKind::InvalidState.into())
         }
     }
 
@@ -139,13 +110,13 @@ impl<S: ChildSpawner> ChildMonitor<S> {
     }
 
     /// Sends a kill signal to the child process.
-    pub fn stop(&self) -> TransitionResult<()> {
+    pub fn stop(&self) -> Result<()> {
         let state_lock = self.state.lock().unwrap();
         if let State::Running(ref running_state) = *state_lock {
-            running_state.child.kill()?;
+            running_state.child.kill().chain_err(|| ErrorKind::Kill)?;
             Ok(())
         } else {
-            Err(TransitionError::InvalidState)
+            Err(ErrorKind::InvalidState.into())
         }
     }
 }