tsort: refactor error handling

Author: dragutreis

src/uu/tsort/locales/en-US.ftl

@@ -9,3 +9,5 @@ tsort-error-loop = input contains a loop:
 tsort-error-extra-operand = extra operand { $operand }
   Try '{ $util } --help' for more information.
 tsort-error-at-least-one-input = at least one input
+tsort-error-read = read error: { $error }
+tsort-error-write = write error: { $error }

src/uu/tsort/locales/fr-FR.ftl

@@ -9,3 +9,5 @@ tsort-error-loop = l'entrée contient une boucle :
 tsort-error-extra-operand = opérande supplémentaire { $operand }
   Essayez '{ $util } --help' pour plus d'informations.
 tsort-error-at-least-one-input = au moins une entrée
+tsort-error-read = erreur de lecture : { $error }
+tsort-error-write = erreur d'écriture : { $error }

src/uu/tsort/src/tsort.rs

@@ -15,7 +15,7 @@ use string_interner::StringInterner;
 use string_interner::backend::BucketBackend;
 use thiserror::Error;
 use uucore::display::Quotable;
-use uucore::error::{UError, UResult, USimpleError};
+use uucore::error::{UError, UResult, USimpleError, strip_errno};
 use uucore::{format_usage, show, translate};
 
 // short types for switching interning behavior on the fly.
@@ -102,7 +102,7 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
         process_input(reader, &mut g)?;
     }
 
-    g.run_tsort().map_err(|e| USimpleError::new(1, format!("write error: {e}")))?;
+    g.run_tsort()?;
     Ok(())
 }
 
@@ -151,6 +151,12 @@ enum TsortError {
     /// Wrapper for bubbling up IO errors
     #[error("{0}")]
     IO(#[from] io::Error),
+    /// Read error.
+    #[error("{}", translate!("tsort-error-read", "error" => strip_errno(.0)))]
+    Read(io::Error),
+    /// Write error.
+    #[error("{}", translate!("tsort-error-write", "error" => strip_errno(.0)))]
+    Write(io::Error),
 }
 
 // Auxiliary struct, just for printing loop nodes via show! macro
@@ -173,7 +179,7 @@ fn process_input<R: BufRead>(reader: R, graph: &mut Graph) -> Result<(), TsortEr
             if e.kind() == io::ErrorKind::IsADirectory {
                 TsortError::IsDir(graph.name())
             } else {
-                e.into()
+                TsortError::Read(e)
             }
         })?;
         for token in line.split_whitespace() {
@@ -276,7 +282,7 @@ impl Graph {
     }
 
     /// Implementation of algorithm T from TAOCP (Don. Knuth), vol. 1.
-    fn run_tsort(&mut self) -> io::Result<()> {
+    fn run_tsort(&mut self) -> Result<(), TsortError> {
         let mut independent_nodes_queue: VecDeque<Sym> = self
             .nodes
             .iter()
@@ -321,7 +327,7 @@ impl Graph {
             }
         }
 
-        res
+        res.map_err(TsortError::Write)
     }
     pub fn indegree(&self, sym: Sym) -> Option<usize> {
         self.nodes.get(&sym).map(|data| data.predecessor_count)