process: Simplify child IO registration

src/lib.rs

@@ -164,7 +164,7 @@ extern crate tokio_reactor;
 extern crate mio;
 
 use std::io::{self, Read, Write};
-use std::process::{self, ExitStatus, Output, Stdio};
+use std::process::{Command, ExitStatus, Output, Stdio};
 
 use futures::{Future, Poll, IntoFuture};
 use futures::future::{Either, ok};
@@ -320,25 +320,16 @@ pub trait CommandExt {
 }
 
 
-impl CommandExt for process::Command {
+impl CommandExt for Command {
     fn spawn_async_with_handle(&mut self, handle: &Handle) -> io::Result<Child> {
-        let mut child = Child {
-            child: imp::Child::new(try!(self.spawn()), handle),
-            stdin: None,
-            stdout: None,
-            stderr: None,
-            kill_on_drop: true,
-        };
-        child.stdin = try!(child.child.register_stdin(handle)).map(|io| {
-            ChildStdin { inner: io }
-        });
-        child.stdout = try!(child.child.register_stdout(handle)).map(|io| {
-            ChildStdout { inner: io }
-        });
-        child.stderr = try!(child.child.register_stderr(handle)).map(|io| {
-            ChildStderr { inner: io }
-        });
-        Ok(child)
+        imp::Child::new(self.spawn()?, handle)
+            .map(|(child, stdin, stdout, stderr)| Child {
+                child,
+                stdin: stdin.map(|inner| ChildStdin { inner }),
+                stdout: stdout.map(|inner| ChildStdout { inner }),
+                stderr: stderr.map(|inner| ChildStderr { inner }),
+                kill_on_drop: true,
+            })
     }
 
     fn status_async_with_handle(&mut self, handle: &Handle) -> io::Result<StatusAsync> {

src/unix/mod.rs

@@ -58,27 +58,20 @@ impl fmt::Debug for Child {
 }
 
 impl Child {
-    pub fn new(inner: process::Child, handle: &Handle) -> Child {
-        Child {
+    pub fn new(mut inner: process::Child, handle: &Handle)
+        -> io::Result<(Child, Option<ChildStdin>, Option<ChildStdout>, Option<ChildStderr>)>
+    {
+        let stdin = stdio(inner.stdin.take(), handle)?;
+        let stdout = stdio(inner.stdout.take(), handle)?;
+        let stderr = stdio(inner.stderr.take(), handle)?;
+
+        let child = Child {
             inner: inner,
             reaped: false,
             sigchld: Signal::with_handle(libc::SIGCHLD, handle).flatten_stream(),
-        }
-    }
+        };
 
-    pub fn register_stdin(&mut self, handle: &Handle)
-                          -> io::Result<Option<ChildStdin>> {
-        stdio(self.inner.stdin.take(), handle)
-    }
-
-    pub fn register_stdout(&mut self, handle: &Handle)
-                           -> io::Result<Option<ChildStdout>> {
-        stdio(self.inner.stdout.take(), handle)
-    }
-
-    pub fn register_stderr(&mut self, handle: &Handle)
-                           -> io::Result<Option<ChildStderr>> {
-        stdio(self.inner.stderr.take(), handle)
+        Ok((child, stdin, stdout, stderr))
     }
 
     pub fn id(&self) -> u32 {

src/windows.rs

@@ -64,26 +64,19 @@ unsafe impl Sync for Waiting {}
 unsafe impl Send for Waiting {}
 
 impl Child {
-    pub fn new(child: process::Child, _handle: &Handle) -> Child {
-        Child {
-            child: child,
+    pub fn new(mut inner: process::Child, handle: &Handle)
+        -> io::Result<(Child, Option<ChildStdin>, Option<ChildStdout>, Option<ChildStderr>)>
+    {
+        let stdin = stdio(inner.stdin.take(), handle)?;
+        let stdout = stdio(inner.stdout.take(), handle)?;
+        let stderr = stdio(inner.stderr.take(), handle)?;
+
+        let child = Child {
+            child: inner,
             waiting: None,
-        }
-    }
+        };
 
-    pub fn register_stdin(&mut self, handle: &Handle)
-                          -> io::Result<Option<ChildStdin>> {
-        stdio(self.child.stdin.take(), handle)
-    }
-
-    pub fn register_stdout(&mut self, handle: &Handle)
-                           -> io::Result<Option<ChildStdout>> {
-        stdio(self.child.stdout.take(), handle)
-    }
-
-    pub fn register_stderr(&mut self, handle: &Handle)
-                           -> io::Result<Option<ChildStderr>> {
-        stdio(self.child.stderr.take(), handle)
+        Ok((child, stdin, stdout, stderr))
     }
 
     pub fn id(&self) -> u32 {