wc: stop processing --files0-from input after stdout write failure (#11023)

* fix(wc): stop processing after stdout write error

When wc encounters a write error to stdout (e.g., when stdout is redirected to /dev/full), it should stop processing immediately rather than continuing to process remaining files. This matches GNU wc behavior and prevents unnecessary processing after the output is already broken.

* fix(wc): improve error message matching in test_files0_stops_after_stdout_write_error

Author: mattsu2020

src/uu/wc/src/wc.rs

@@ -988,6 +988,7 @@ fn wc(inputs: &Inputs, settings: &Settings) -> UResult<()> {
             if let Err(err) = print_stats(settings, &word_count, maybe_title_str, number_width) {
                 let title = maybe_title_str.unwrap_or(OsStr::new("<stdin>"));
                 show!(err.map_err_context(|| translate!("wc-error-failed-to-print-result", "title" => title.to_string_lossy())));
+                return Ok(());
             }
         }
         // Print deferred error after stats to match GNU wc output order

tests/by-util/test_wc.rs

@@ -763,6 +763,30 @@ fn test_files0_progressive_stream() {
         .stdout_only("36 370 2189 total\n");
 }
 
+#[cfg(target_os = "linux")]
+#[test]
+fn test_files0_stops_after_stdout_write_error() {
+    use std::fs::OpenOptions;
+
+    let dev_full = OpenOptions::new().write(true).open("/dev/full").unwrap();
+
+    let stderr = new_ucmd!()
+        .args(&["--files0-from=-", "--total=never"])
+        .set_stdout(dev_full)
+        .pipe_in(b"/dev/null\0/dev/null\0/dev/null\0")
+        .fails()
+        .stderr_str()
+        .to_string();
+
+    assert_eq!(
+        stderr
+            .matches("failed to print result for /dev/null")
+            .count(),
+        1,
+        "wc should stop after the first stdout write error: {stderr:?}"
+    );
+}
+
 #[test]
 fn files0_from_dir() {
     // On Unix, `read(open("."))` fails. On Windows, `open(".")` fails. Thus, the errors happen in