chgrp: reject the :gid format for the group operand

src/uu/chgrp/src/chgrp.rs

@@ -27,21 +27,26 @@ enum ChgrpError {
 
 impl UError for ChgrpError {}
 
+fn parse_group(group: &str) -> Result<u32, String> {
+    // Try as group name first
+    match entries::grp2gid(group) {
+        Ok(g) => Ok(g),
+        // If group name lookup fails, try parsing as raw number
+        Err(_) => group
+            .parse::<u32>()
+            .map_err(|_| translate!("chgrp-error-invalid-group", "group" => group)),
+    }
+}
+
+/// Parse the `--from` value, which also accepts the `:gid` format.
 fn parse_gid_from_str(group: &str) -> Result<u32, String> {
     if let Some(gid_str) = group.strip_prefix(':') {
         // Handle :gid format
         gid_str
             .parse::<u32>()
             .map_err(|_| translate!("chgrp-error-invalid-group-id", "gid_str" => gid_str))
     } else {
-        // Try as group name first
-        match entries::grp2gid(group) {
-            Ok(g) => Ok(g),
-            // If group name lookup fails, try parsing as raw number
-            Err(_) => group
-                .parse::<u32>()
-                .map_err(|_| translate!("chgrp-error-invalid-group", "group" => group)),
-        }
+        parse_group(group)
     }
 }
 
@@ -67,7 +72,8 @@ fn get_dest_gid(matches: &ArgMatches) -> UResult<(Option<u32>, String)> {
         if group.is_empty() {
             None
         } else {
-            match parse_gid_from_str(group) {
+            // Unlike --from, GNU does not accept the `:gid` format here.
+            match parse_group(group) {
                 Ok(g) => Some(g),
                 Err(e) => return Err(USimpleError::new(1, e)),
             }

tests/by-util/test_chgrp.rs

@@ -62,6 +62,18 @@ fn test_invalid_group() {
         .stderr_is("chgrp: invalid group: '__nosuchgroup__'\n");
 }
 
+#[test]
+fn test_invalid_group_with_colon_prefix() {
+    // The `:gid` format is only accepted by --from, not for the group operand
+    let (at, mut ucmd) = at_and_ucmd!();
+    at.touch("file");
+    let gid = getegid().as_raw();
+    ucmd.arg(format!(":{gid}"))
+        .arg("file")
+        .fails_with_code(1)
+        .stderr_is(format!("chgrp: invalid group: ':{gid}'\n"));
+}
+
 #[test]
 fn test_error_1() {
     if !getegid().is_root() {
@@ -604,11 +616,11 @@ fn test_numeric_group_formats() {
     let new_gid = at.plus("test_file").metadata().unwrap().gid();
     assert_eq!(new_gid, second_group.as_raw());
 
-    // Test :gid format in target group
+    // Test numeric gid in target group (the :gid format is only valid for --from)
     scene
         .ucmd()
         .arg(format!("--from={}", second_group.as_raw()))
-        .arg(format!(":{}", first_group.as_raw()))
+        .arg(first_group.as_raw().to_string())
         .arg("test_file")
         .succeeds()
         .no_stderr();