sort: reject conflicting --compress-program values

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

@@ -24,6 +24,7 @@ sort-file-operands-combined = extra operand {$file}
     file operands cannot be combined with --files0-from
     Try '{$help} --help' for more information.
 sort-multiple-output-files = multiple output files specified
+sort-multiple-compress-programs = multiple compress programs specified
 sort-incompatible-tabs = incompatible tabs
 sort-minus-in-stdin = when reading file names from standard input, no file name of '-' allowed
 sort-no-input-from = no input from {$file}

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

@@ -24,6 +24,7 @@ sort-file-operands-combined = opérande supplémentaire {$file}
     les opérandes de fichier ne peuvent pas être combinées avec --files0-from
     Essayez '{$help} --help' pour plus d'informations.
 sort-multiple-output-files = plusieurs fichiers de sortie spécifiés
+sort-multiple-compress-programs = plusieurs programmes de compression spécifiés
 sort-incompatible-tabs = tabulations incompatibles
 sort-minus-in-stdin = lors de la lecture des noms de fichiers depuis l'entrée standard, aucun nom de fichier '-' n'est autorisé
 sort-no-input-from = aucune entrée depuis {$file}

src/uu/sort/src/sort.rs

@@ -185,6 +185,9 @@ pub enum SortError {
     #[error("{}", translate!("sort-multiple-output-files"))]
     MultipleOutputFiles,
 
+    #[error("{}", translate!("sort-multiple-compress-programs"))]
+    MultipleCompressPrograms,
+
     #[error("{}", translate!("sort-incompatible-tabs"))]
     IncompatibleTabs,
 
@@ -2179,6 +2182,11 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
         return Err(SortError::MultipleOutputFiles.into());
     }
 
+    // Same as -o: repeating --compress-program is fine as long as the value is the same
+    if has_conflicting_values::<String>(&matches, options::COMPRESS_PROG) {
+        return Err(SortError::MultipleCompressPrograms.into());
+    }
+
     // Prevent -t/--field-separator from being given different values. Raw
     // values suffice: `\0` is the only spelling rewritten later, and argv cannot hold a NUL.
     if has_conflicting_values::<OsString>(&matches, options::SEPARATOR) {
@@ -2725,7 +2733,9 @@ pub fn uu_app() -> Command {
             .long(options::COMPRESS_PROG)
             .help(translate!("sort-help-compress-prog"))
             .value_name("PROG")
-            .value_hint(clap::ValueHint::CommandName),
+            .value_hint(clap::ValueHint::CommandName)
+            // To detect multiple occurrences and raise an error
+            .action(ArgAction::Append),
     )
     .arg(
         Arg::new(options::BATCH_SIZE)

tests/by-util/test_sort.rs

@@ -2448,6 +2448,24 @@ fn test_same_output_flag_twice_ok() {
         .no_stderr();
 }
 
+#[test]
+fn test_error_on_multiple_compress_programs() {
+    new_ucmd!()
+        .args(&["--compress-program", "pwd", "--compress-program", "python3"])
+        .fails_with_code(2)
+        .stderr_only("sort: multiple compress programs specified\n");
+}
+
+#[test]
+fn test_same_compress_program_twice_ok() {
+    // The input is far below the buffer size, so the program is never spawned.
+    new_ucmd!()
+        .args(&["--compress-program", "gzip", "--compress-program", "gzip"])
+        .pipe_in("b\na\n")
+        .succeeds()
+        .stdout_only("a\nb\n");
+}
+
 #[test]
 fn test_output_file_with_leading_dash() {
     let test_cases = [