expand: add support for "--tabs" shortcuts

Fixes #3575

src/uu/expand/src/expand.rs

@@ -7,13 +7,14 @@
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
 
-// spell-checker:ignore (ToDO) ctype cwidth iflag nbytes nspaces nums tspaces uflag
+// spell-checker:ignore (ToDO) ctype cwidth iflag nbytes nspaces nums tspaces uflag Preprocess
 
 #[macro_use]
 extern crate uucore;
 
 use clap::{crate_version, Arg, ArgMatches, Command};
 use std::error::Error;
+use std::ffi::OsString;
 use std::fmt;
 use std::fs::File;
 use std::io::{stdin, stdout, BufRead, BufReader, BufWriter, Read, Write};
@@ -21,7 +22,7 @@ use std::num::IntErrorKind;
 use std::str::from_utf8;
 use unicode_width::UnicodeWidthChar;
 use uucore::display::Quotable;
-use uucore::error::{FromIo, UError, UResult};
+use uucore::error::{FromIo, UError, UResult, UUsageError};
 use uucore::format_usage;
 
 static ABOUT: &str = "Convert tabs in each FILE to spaces, writing to standard output.
@@ -61,6 +62,11 @@ fn is_space_or_comma(c: char) -> bool {
     c == ' ' || c == ','
 }
 
+/// Decide whether the character is either a digit or a comma.
+fn is_digit_or_comma(c: char) -> bool {
+    c.is_ascii_digit() || c == ','
+}
+
 /// Errors that can occur when parsing a `--tabs` argument.
 #[derive(Debug)]
 enum ParseError {
@@ -243,9 +249,35 @@ impl Options {
     }
 }
 
+/// Preprocess command line arguments and expand shortcuts. For example, "-7" is expanded to
+/// "--tabs=7" and "-1,3" to "--tabs=1 --tabs=3".
+fn expand_shortcuts<'a>(
+    mut args: impl uucore::Args + 'a,
+) -> Result<Box<dyn Iterator<Item = OsString> + 'a>, Box<(dyn UError + 'static)>> {
+    // argv[0] is always present
+    let mut processed_args = vec![args.next().unwrap()];
+
+    for arg in args {
+        if let Some(s) = arg.to_str() {
+            if s.starts_with('-') && s[1..].chars().all(is_digit_or_comma) {
+                s[1..]
+                    .split(',')
+                    .filter(|s| !s.is_empty())
+                    .for_each(|s| processed_args.push(format!("--tabs={}", s).into()));
+            } else {
+                processed_args.push(arg);
+            }
+        } else {
+            return Err(UUsageError::new(1, "bad argument encoding".to_owned()));
+        }
+    }
+
+    Ok(Box::new(processed_args.into_iter()))
+}
+
 #[uucore::main]
 pub fn uumain(args: impl uucore::Args) -> UResult<()> {
-    let matches = uu_app().get_matches_from(args);
+    let matches = uu_app().get_matches_from(expand_shortcuts(args)?);
 
     expand(&Options::new(&matches)?).map_err_context(|| "failed to write output".to_string())
 }
@@ -445,6 +477,8 @@ fn expand(options: &Options) -> std::io::Result<()> {
 
 #[cfg(test)]
 mod tests {
+    use crate::is_digit_or_comma;
+
     use super::next_tabstop;
     use super::RemainingMode;
 
@@ -468,4 +502,11 @@ mod tests {
         assert_eq!(next_tabstop(&[1, 5], 3, &RemainingMode::Slash), 2);
         assert_eq!(next_tabstop(&[1, 5], 6, &RemainingMode::Slash), 4);
     }
+
+    #[test]
+    fn test_is_digit_or_comma() {
+        assert!(is_digit_or_comma('1'));
+        assert!(is_digit_or_comma(','));
+        assert!(!is_digit_or_comma('a'));
+    }
 }

tests/by-util/test_expand.rs

@@ -263,3 +263,33 @@ fn test_tabs_with_too_large_size() {
 
     new_ucmd!().arg(arg).fails().stderr_contains(expected_error);
 }
+
+#[test]
+fn test_tabs_shortcut() {
+    new_ucmd!()
+        .args(&["-2", "-5", "-7"])
+        .pipe_in("\ta\tb\tc")
+        .succeeds()
+        //          01234567890
+        .stdout_is("  a  b c");
+}
+
+#[test]
+fn test_comma_separated_tabs_shortcut() {
+    new_ucmd!()
+        .args(&["-2,5", "-7"])
+        .pipe_in("\ta\tb\tc")
+        .succeeds()
+        //          01234567890
+        .stdout_is("  a  b c");
+}
+
+#[test]
+fn test_tabs_and_tabs_shortcut_mixed() {
+    new_ucmd!()
+        .args(&["-2", "--tabs=5", "-7"])
+        .pipe_in("\ta\tb\tc")
+        .succeeds()
+        //          01234567890
+        .stdout_is("  a  b c");
+}