clean up error handling

By adding an implicit conversion from std::io::Error to SessionError, a
lot of the .or(SessionError) bits can be dropped.

1 files changed, 12 insertions, 7 deletions

diff --git a/src/lib.rs b/src/lib.rs
index 1b55c8f..73cd9b0 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -27,20 +27,25 @@ fn create_and_open_dir<P: AsRef<Path> + Copy>(
 
 struct SessionError;
 
+impl From<std::io::Error> for SessionError {
+    fn from(_: std::io::Error) -> Self {
+        SessionError
+    }
+}
+
 fn open_session(h: &mut PamHandle) -> Result<(), SessionError> {
     let user = h.get_user(None).or(Err(SessionError))?;
     let user = users::get_user_by_name(&user).ok_or(SessionError)?;
     let aa = cap_std::ambient_authority();
-    let d = Dir::open_ambient_dir(CG_MOUNT, aa).or(Err(SessionError))?;
-    let d = create_and_open_dir(&d, "user").or(Err(SessionError))?;
-    let d = create_and_open_dir(&d, &user.uid().to_string())
-        .or(Err(SessionError))?;
-    let d = create_and_open_dir(&d, "leaf").or(Err(SessionError))?;
+    let d = Dir::open_ambient_dir(CG_MOUNT, aa)?;
+    let d = create_and_open_dir(&d, "user")?;
+    let d = create_and_open_dir(&d, &user.uid().to_string())?;
+    let d = create_and_open_dir(&d, "leaf")?;
     let pid = process::id().to_string();
     let mut options = OpenOptions::new();
     options.write(true);
-    let mut procs = d.open_with("cgroup.procs", &options).or(Err(SessionError))?;
-    procs.write_all(pid.as_bytes()).or(Err(SessionError))?;
+    let mut procs = d.open_with("cgroup.procs", &options)?;
+    procs.write_all(pid.as_bytes())?;
     Ok(())
 }