stat: handle error better. should make tests/stat/stat-printf.pl pass

src/uu/stat/src/stat.rs

@@ -563,6 +563,15 @@ impl Stater {
         if let Some((field_width, offset)) = format_str[j..].scan_num::<usize>() {
             width = field_width;
             j += offset;
+
+            // Reject directives like `%<NUMBER>` by checking if width has been parsed.
+            if j >= bound || chars[j] == '%' {
+                let invalid_directive: String = chars[old..=j.min(bound - 1)].iter().collect();
+                return Err(USimpleError::new(
+                    1,
+                    format!("{}: invalid directive", invalid_directive.quote()),
+                ));
+            }
         }
         check_bound(format_str, bound, old, j)?;
 

tests/by-util/test_stat.rs

@@ -412,3 +412,20 @@ fn test_printf_bel_etc() {
         .succeeds()
         .stdout_is_bytes(expected_stdout);
 }
+
+#[test]
+fn test_printf_invalid_directive() {
+    let ts = TestScenario::new(util_name!());
+
+    ts.ucmd()
+        .args(&["--printf=%9", "."])
+        .fails()
+        .code_is(1)
+        .stderr_contains("'%9': invalid directive");
+
+    ts.ucmd()
+        .args(&["--printf=%9%", "."])
+        .fails()
+        .code_is(1)
+        .stderr_contains("'%9%': invalid directive");
+}