sort: reject mixing silent and diagnosing --check modes

src/uu/sort/src/sort.rs

@@ -2382,21 +2382,20 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     settings.line_ending = LineEnding::from_zero_flag(matches.get_flag(options::ZERO_TERMINATED));
     settings.merge = matches.get_flag(options::MERGE);
 
-    settings.check = matches.contains_id(options::check::CHECK);
-    if settings.check && matches.get_flag(options::check::CHECK_SILENT) {
+    let check_modes: Vec<&str> = matches
+        .get_many::<String>(options::check::CHECK)
+        .map(|modes| modes.map(String::as_str).collect())
+        .unwrap_or_default();
+    let check_silent = matches.get_flag(options::check::CHECK_SILENT)
+        || check_modes
+            .iter()
+            .any(|m| matches!(*m, options::check::SILENT | options::check::QUIET));
+    let check_diagnose = check_modes.contains(&options::check::DIAGNOSE_FIRST);
+    if check_silent && check_diagnose {
         return Err(incompatible_options_error("cC"));
     }
-    if matches.get_flag(options::check::CHECK_SILENT)
-        || matches!(
-            matches
-                .get_one::<String>(options::check::CHECK)
-                .map(String::as_str),
-            Some(options::check::SILENT | options::check::QUIET)
-        )
-    {
-        settings.check_silent = true;
-        settings.check = true;
-    }
+    settings.check = check_silent || check_diagnose;
+    settings.check_silent = check_silent;
 
     if matches.contains_id(options::OUTPUT) && settings.check {
         let opts = if settings.check_silent { "Co" } else { "co" };
@@ -2605,6 +2604,8 @@ pub fn uu_app() -> Command {
             .long(options::check::CHECK)
             .require_equals(true)
             .num_args(0..)
+            .default_missing_value(options::check::DIAGNOSE_FIRST)
+            .action(ArgAction::Append)
             .value_parser(ShortcutValueParser::new([
                 options::check::SILENT,
                 options::check::QUIET,

tests/by-util/test_sort.rs

@@ -1579,6 +1579,40 @@ fn test_check_silent() {
     }
 }
 
+#[test]
+fn test_check_repeated_modes() {
+    for args in [
+        ["--check=silent", "--check=diagnose-first"],
+        ["-c=silent", "-c=diagnose-first"],
+        ["--check=diagnose-first", "--check=quiet"],
+        ["-c", "--check=quiet"],
+        ["--check=silent", "-c"],
+    ] {
+        new_ucmd!()
+            .args(&args)
+            .arg("check_fail.txt")
+            .fails_with_code(2)
+            .stderr_only("sort: options '-cC' are incompatible\n");
+    }
+
+    for args in [
+        ["--check=quiet", "-C"],
+        ["-C", "--check=silent"],
+        ["--check=quiet", "--check=silent"],
+    ] {
+        new_ucmd!()
+            .args(&args)
+            .arg("check_fail.txt")
+            .fails_with_code(1)
+            .no_output();
+    }
+
+    new_ucmd!()
+        .args(&["--check=diagnose-first", "-c", "check_fail.txt"])
+        .fails_with_code(1)
+        .stderr_only("sort: check_fail.txt:6: disorder: 5\n");
+}
+
 #[test]
 fn test_check_stops_early_without_panicking() {
     // `--check` returns as soon as it finds the first disorder. That used to drop the