sort: point the caret at the failing part of the -S size

Author: sylvestre

docs/src/extensions-errors.md

@@ -276,7 +276,7 @@ the difference:
 | `mknod`  | the failing part of the mode given to `-m`/`--mode` | [`mknod -m u+q mydev c 1 3`](https://uutils.org/playground/?cmd=mknod+-m+u%2Bq+mydev+c+1+3) |
 | `install`| the failing part of the mode given to `-m`/`--mode` | [`install -m u+q fruits.txt dest`](https://uutils.org/playground/?cmd=install+-m+u%2Bq+fruits.txt+dest) |
 | `tr`     | the part of a set that is at fault (bad class, backwards range, bad repeat count, …) | [`tr 'qw[y-b]' x`](https://uutils.org/playground/?cmd=tr+%27qw%5By-b%5D%27+x) |
-| `sort`   | the failing part of a `-k`/`--key` or field specification | [`sort -k2.3x fruits.txt`](https://uutils.org/playground/?cmd=sort+-k2.3x+fruits.txt) |
+| `sort`   | the failing part of a `-k`/`--key` or field specification, or of the SIZE given to `-S` | [`sort -k2.3x fruits.txt`](https://uutils.org/playground/?cmd=sort+-k2.3x+fruits.txt) |
 | `numfmt` | the failing part of a `--field` or `--format` specification | [`numfmt --format=%q 1000`](https://uutils.org/playground/?cmd=numfmt+--format%3D%25q+1000) |
 | `printf` | the failing conversion or escape in the format string | [`printf %5.2c q`](https://uutils.org/playground/?cmd=printf+%255.2c+q) |
 | `env`    | the failing part of a `-S`/`--split-string` string | [`env -S 'echo ${1FOO}'`](https://uutils.org/playground/?cmd=env+-S+%27echo+%24%7B1FOO%7D%27) |
@@ -335,7 +335,7 @@ repeated per utility. Three parsers work this way:
   `numfmt --field`. `Range::from_list` reports which item of the list failed
   and where it sat.
 - **Sizes** (`uucore::parser::parse_size`), for `head`, `tail`, `truncate`,
-  `split`, `shred` and `stdbuf` today, and available to the other callers of the parser.
+  `split`, `shred`, `stdbuf` and `sort` today, and available to the other callers of the parser.
   `ParseSizeError::span` works out from the operand which of its two parts —
   the number or the unit — was rejected, so the error type keeps the shape its
   callers build by hand.

src/uu/sort/src/sort.rs

@@ -2228,8 +2228,17 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     }
 
     if let Some(size_str) = matches.get_one::<String>(options::BUF_SIZE) {
-        settings.buffer_size = GlobalSettings::parse_byte_count(size_str).map_err(|e| {
-            USimpleError::new(2, format_error_message(&e, size_str, options::BUF_SIZE))
+        settings.buffer_size = GlobalSettings::parse_byte_count(size_str).map_err(|error| {
+            let message = format_error_message(&error, size_str, options::BUF_SIZE);
+            error.size_value_error(
+                key_args.as_deref(),
+                size_str,
+                0,
+                'S',
+                options::BUF_SIZE,
+                &message,
+                USimpleError::new(2, message.clone()),
+            )
         })?;
         settings.buffer_size_is_explicit = true;
     } else {

tests/by-util/test_sort.rs

@@ -3361,6 +3361,30 @@ sort: invalid number at field start: invalid count at start of 'sort'
         );
     }
 
+    #[cfg(unix)]
+    #[test]
+    fn test_snippet_points_at_the_unknown_unit_of_a_buffer_size() {
+        let result = new_ucmd!()
+            .terminal_sim_stderr()
+            .args(&["-S", "8zz", "/dev/null"])
+            .fails_with_code(2);
+
+        // The number parsed; only the unit did not.
+        assert_eq!(
+            result.stderr_as_displayed(),
+            "\
+sort: invalid suffix in --buffer-size argument '8zz'
+   ╭─[ sort:1:10 ]
+   │
+ 1 │ sort -S 8zz /dev/null
+   │          ─┬
+   │           ╰── not a known unit
+   │
+   │ Help: a size is a number and an optional unit: K, M, G and so on for 1024, KB, MB, GB for 1000
+───╯"
+        );
+    }
+
     #[test]
     fn test_plain_message_when_stderr_is_not_a_terminal() {
         // The test harness pipes stderr, so the report must not appear.
@@ -3370,6 +3394,10 @@ sort: invalid number at field start: invalid count at start of 'sort'
             .stderr_only(
                 "sort: stray character in field spec: invalid field specification '2.3q'\n",
             );
+        new_ucmd!()
+            .args(&["-S", "8zz", "/dev/null"])
+            .fails_with_code(2)
+            .stderr_only("sort: invalid suffix in --buffer-size argument '8zz'\n");
     }
 }