head: refactor to use specific error enums

Cargo.lock

@@ -2770,6 +2770,7 @@ version = "0.0.28"
 dependencies = [
  "clap",
  "memchr",
+ "thiserror 2.0.9",
  "uucore",
 ]
 

src/uu/head/Cargo.toml

@@ -19,6 +19,7 @@ path = "src/head.rs"
 [dependencies]
 clap = { workspace = true }
 memchr = { workspace = true }
+thiserror = { workspace = true }
 uucore = { workspace = true, features = ["ringbuffer", "lines", "fs"] }
 
 [[bin]]

src/uu/head/src/head.rs

@@ -8,8 +8,10 @@
 use clap::{crate_version, Arg, ArgAction, ArgMatches, Command};
 use std::ffi::OsString;
 use std::io::{self, BufWriter, ErrorKind, Read, Seek, SeekFrom, Write};
+use std::num::TryFromIntError;
+use thiserror::Error;
 use uucore::display::Quotable;
-use uucore::error::{FromIo, UResult, USimpleError};
+use uucore::error::{FromIo, UError, UResult};
 use uucore::line_ending::LineEnding;
 use uucore::lines::lines;
 use uucore::{format_usage, help_about, help_usage, show};
@@ -37,6 +39,36 @@ mod take;
 use take::take_all_but;
 use take::take_lines;
 
+#[derive(Error, Debug)]
+enum HeadError {
+    /// Wrapper around `io::Error`
+    #[error("error reading {name}: {err}")]
+    Io { name: String, err: io::Error },
+
+    #[error("parse error: {0}")]
+    ParseError(String),
+
+    #[error("bad argument encoding")]
+    BadEncoding,
+
+    #[error("{0}: number of -bytes or -lines is too large")]
+    NumTooLarge(#[from] TryFromIntError),
+
+    #[error("clap error: {0}")]
+    Clap(#[from] clap::Error),
+
+    #[error("{0}")]
+    MatchOption(String),
+}
+
+impl UError for HeadError {
+    fn code(&self) -> i32 {
+        1
+    }
+}
+
+type HeadResult<T> = Result<T, HeadError>;
+
 pub fn uu_app() -> Command {
     Command::new(uucore::util_name())
         .version(crate_version!())
@@ -152,7 +184,7 @@ impl Mode {
 
 fn arg_iterate<'a>(
     mut args: impl uucore::Args + 'a,
-) -> UResult<Box<dyn Iterator<Item = OsString> + 'a>> {
+) -> HeadResult<Box<dyn Iterator<Item = OsString> + 'a>> {
     // argv[0] is always present
     let first = args.next().unwrap();
     if let Some(second) = args.next() {
@@ -160,22 +192,19 @@ fn arg_iterate<'a>(
             match parse::parse_obsolete(s) {
                 Some(Ok(iter)) => Ok(Box::new(vec![first].into_iter().chain(iter).chain(args))),
                 Some(Err(e)) => match e {
-                    parse::ParseError::Syntax => Err(USimpleError::new(
-                        1,
-                        format!("bad argument format: {}", s.quote()),
-                    )),
-                    parse::ParseError::Overflow => Err(USimpleError::new(
-                        1,
-                        format!(
-                            "invalid argument: {} Value too large for defined datatype",
-                            s.quote()
-                        ),
-                    )),
+                    parse::ParseError::Syntax => Err(HeadError::ParseError(format!(
+                        "bad argument format: {}",
+                        s.quote()
+                    ))),
+                    parse::ParseError::Overflow => Err(HeadError::ParseError(format!(
+                        "invalid argument: {} Value too large for defined datatype",
+                        s.quote()
+                    ))),
                 },
                 None => Ok(Box::new(vec![first, second].into_iter().chain(args))),
             }
         } else {
-            Err(USimpleError::new(1, "bad argument encoding".to_owned()))
+            Err(HeadError::BadEncoding)
         }
     } else {
         Ok(Box::new(vec![first].into_iter()))
@@ -247,10 +276,7 @@ fn catch_too_large_numbers_in_backwards_bytes_or_lines(n: u64) -> Option<usize>
     match usize::try_from(n) {
         Ok(value) => Some(value),
         Err(e) => {
-            show!(USimpleError::new(
-                1,
-                format!("{e}: number of -bytes or -lines is too large")
-            ));
+            show!(HeadError::NumTooLarge(e));
             None
         }
     }
@@ -511,16 +537,17 @@ fn uu_head(options: &HeadOptions) -> UResult<()> {
                 head_file(&mut file, options)
             }
         };
-        if res.is_err() {
+        if let Err(e) = res {
             let name = if file.as_str() == "-" {
                 "standard input"
             } else {
                 file
             };
-            show!(USimpleError::new(
-                1,
-                format!("error reading {name}: Input/output error")
-            ));
+            return Err(HeadError::Io {
+                name: name.to_string(),
+                err: e,
+            }
+            .into());
         }
         first = false;
     }
@@ -537,7 +564,7 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     let args = match HeadOptions::get_from(&matches) {
         Ok(o) => o,
         Err(s) => {
-            return Err(USimpleError::new(1, s));
+            return Err(HeadError::MatchOption(s).into());
         }
     };
     uu_head(&args)