wc:Ensure the output order of stdout and stderror remains unchanged. (#9905)

---------

Co-authored-by: Sylvestre Ledru <sylvestre@debian.org>

src/uu/wc/src/wc.rs

@@ -950,12 +950,13 @@ fn wc(inputs: &Inputs, settings: &Settings) -> UResult<()> {
             }
         };
 
-        let word_count = match word_count_from_input(&input, settings) {
-            CountResult::Success(word_count) => word_count,
-            CountResult::Interrupted(word_count, err) => {
-                show!(err.map_err_context(|| input.path_display()));
-                word_count
-            }
+        // Store any I/O error from reading to print AFTER stats (matches GNU wc behavior)
+        let (word_count, deferred_error) = match word_count_from_input(&input, settings) {
+            CountResult::Success(word_count) => (word_count, None),
+            CountResult::Interrupted(word_count, err) => (
+                word_count,
+                Some(err.map_err_context(|| input.path_display())),
+            ),
             CountResult::Failure(err) => {
                 show!(err.map_err_context(|| input.path_display()));
                 continue;
@@ -970,6 +971,11 @@ fn wc(inputs: &Inputs, settings: &Settings) -> UResult<()> {
                 show!(err.map_err_context(|| translate!("wc-error-failed-to-print-result", "title" => title.to_string_lossy())));
             }
         }
+        // Print deferred error after stats to match GNU wc output order
+        if let Some(err) = deferred_error {
+            let _ = io::stdout().flush();
+            show!(err);
+        }
     }
 
     if settings.total_when.is_total_row_visible(num_inputs) {

tests/by-util/test_wc.rs

@@ -8,7 +8,7 @@ use uutests::at_and_ucmd;
 use uutests::new_ucmd;
 use uutests::util::vec_of_size;
 
-// spell-checker:ignore (flags) lwmcL clmwL ; (path) bogusfile emptyfile manyemptylines moby notrailingnewline onelongemptyline onelongword weirdchars
+// spell-checker:ignore (flags) lwmcL clmwL ; (path) bogusfile emptyfile manyemptylines moby notrailingnewline onelongemptyline onelongword weirdchars ioerrdir
 #[test]
 fn test_invalid_arg() {
     new_ucmd!().arg("--definitely-invalid").fails_with_code(1);
@@ -449,6 +449,23 @@ fn test_read_from_directory_error() {
         .stdout_is(STDOUT);
 }
 
+#[cfg(unix)]
+#[test]
+fn test_read_error_order_with_stderr_to_stdout() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    at.mkdir("ioerrdir");
+
+    let expected = format!(
+        "{:>7} {:>7} {:>7} ioerrdir\nwc: ioerrdir: Is a directory\n",
+        0, 0, 0
+    );
+
+    ucmd.arg("ioerrdir")
+        .stderr_to_stdout()
+        .fails()
+        .stdout_only(expected);
+}
+
 /// Test that getting counts from nonexistent file is an error.
 #[test]
 fn test_read_from_nonexistent_file() {