more descriptive errors

src/error.rs

@@ -15,18 +15,12 @@ pub enum Error {
     #[error("json: {0}")]
     Json(#[from] serde_json::Error),
 
+    #[error("bad pipe specification: a pipe must have exactly one reader and one writer: {0}")]
+    BadPipe(String),
+
     #[error("bad specification type: only .json files are supported")]
     BadSpecType,
 
-    #[error("bad pipe trigger: this entrypoint is not triggered by a pipe")]
-    BadPipeTrigger,
-
-    #[error("too many pipes: a pipe must have one reader and one writer: {0}")]
-    TooManyPipes(String),
-
-    #[error("read only pipe: a pipe must have one reader and one writer: {0}")]
-    ReadOnlyPipe(String),
-
-    #[error("write only pipe: a pipe must have one reader and one writer: {0}")]
-    WriteOnlyPipe(String),
+    #[error("bad trigger argument: this entrypoint is not triggered by something with arguments")]
+    BadTriggerArgument,
 }

src/lib.rs

@@ -79,45 +79,47 @@ pub fn run() -> Result<()> {
     .spawn()
 }
 
+fn create_pipes(names: Vec<&str>) -> Result<HashMap<String, PipePair>> {
+    let mut pipes = HashMap::new();
+    for pipe in names {
+        info!("creating pipe pair `{}`", pipe);
+        pipes.insert(pipe.to_string(), PipePair::new(pipe)?);
+    }
+
+    Ok(pipes)
+}
+
 pub struct PipePair {
+    name: String,
+
     read: Option<File>,
     write: Option<File>,
 }
 
 impl PipePair {
-    fn take_read(&mut self) -> File {
-        self.read
-            .take()
-            .expect("read pipes should only be used once")
-    }
-
-    fn take_write(&mut self) -> File {
-        self.write
-            .take()
-            .expect("write pipes should only be used once")
-    }
-}
-
-fn create_pipes(names: Vec<&str>) -> Result<HashMap<String, PipePair>> {
-    let mut pipes = HashMap::new();
-
-    for pipe in names {
-        info!("creating pipe pair `{}`", pipe);
-
+    fn new(name: &str) -> Result<PipePair> {
         let (read, write) = unistd::pipe2(OFlag::O_DIRECT).map_err(|e| Error::Nix {
             msg: "pipe2",
             src: e,
         })?;
 
         // safe to create files given the successful return of pipe(2)
-        pipes.insert(
-            pipe.to_string(),
-            PipePair {
-                read: Some(unsafe { File::from_raw_fd(read) }),
-                write: Some(unsafe { File::from_raw_fd(write) }),
-            },
-        );
+        Ok(PipePair {
+            name: name.to_string(),
+            read: Some(unsafe { File::from_raw_fd(read) }),
+            write: Some(unsafe { File::from_raw_fd(write) }),
+        })
     }
 
-    Ok(pipes)
+    fn take_read(&mut self) -> Result<File> {
+        self.read
+            .take()
+            .ok_or_else(|| Error::BadPipe(self.name.to_string()))
+    }
+
+    fn take_write(&mut self) -> Result<File> {
+        self.write
+            .take()
+            .ok_or_else(|| Error::BadPipe(self.name.to_string()))
+    }
 }

src/spawner.rs

@@ -55,7 +55,7 @@ impl<'a> Spawner<'a> {
                 }
 
                 Trigger::Pipe(s) => {
-                    let pipe = self.pipes.get_mut(s).unwrap().take_read();
+                    let pipe = self.pipes.get_mut(s).unwrap().take_read().unwrap();
                     let binary = PathBuf::from(self.binary).canonicalize()?;
 
                     let mut builder = VoidBuilder::new();
@@ -126,11 +126,11 @@ impl<'a> Spawner<'a> {
 
                 Arg::Pipe(p) => out.push(match p {
                     Pipe::Rx(s) => {
-                        let pipe = self.pipes.get_mut(s).unwrap().take_read();
+                        let pipe = self.pipes.get_mut(s).unwrap().take_read().unwrap();
                         CString::new(pipe.as_raw_fd().to_string()).unwrap()
                     }
                     Pipe::Tx(s) => {
-                        let pipe = self.pipes.get_mut(s).unwrap().take_write();
+                        let pipe = self.pipes.get_mut(s).unwrap().take_write().unwrap();
                         CString::new(pipe.as_raw_fd().to_string()).unwrap()
                     }
                 }),

src/specification.rs

@@ -122,25 +122,25 @@ impl Specification {
 
         for pipe in read {
             if !read_set.insert(pipe) {
-                return Err(Error::TooManyPipes(pipe.to_string()));
+                return Err(Error::BadPipe(pipe.to_string()));
             }
         }
 
         let mut write_set = HashSet::with_capacity(write.len());
         for pipe in write {
             if !write_set.insert(pipe) {
-                return Err(Error::TooManyPipes(pipe.to_string()));
+                return Err(Error::BadPipe(pipe.to_string()));
             }
         }
 
         for pipe in read_set {
             if !write_set.remove(pipe) {
-                return Err(Error::ReadOnlyPipe(pipe.to_string()));
+                return Err(Error::BadPipe(pipe.to_string()));
             }
         }
 
         if let Some(pipe) = write_set.into_iter().next() {
-            return Err(Error::WriteOnlyPipe(pipe.to_string()));
+            return Err(Error::BadPipe(pipe.to_string()));
         }
 
         // validate pipe trigger arguments make sense
@@ -148,7 +148,7 @@ impl Specification {
             if entrypoint.args.contains(&Arg::PipeTrigger) {
                 match entrypoint.trigger {
                     Trigger::Pipe(_) => {}
-                    _ => return Err(Error::BadPipeTrigger),
+                    _ => return Err(Error::BadTriggerArgument),
                 }
             }
         }