fold: keep zero-width characters after a newline

src/uu/fold/src/fold.rs

@@ -569,6 +569,12 @@ fn process_utf8_chars<W: Write>(line: &str, ctx: &mut FoldContext<'_, W>) -> URe
     let mut iter = line.char_indices().peekable();
 
     while let Some((byte_idx, ch)) = iter.next() {
+        if ch == '\n' {
+            *ctx.last_space = None;
+            emit_output(ctx)?;
+            continue;
+        }
+
         // Include combining characters with the base character when we are
         // measuring by display columns. In character-counting mode every
         // scalar value must advance the counter to match `chars().count()`
@@ -586,12 +592,6 @@ fn process_utf8_chars<W: Write>(line: &str, ctx: &mut FoldContext<'_, W>) -> URe
 
         let next_idx = iter.peek().map_or(line_bytes.len(), |(idx, _)| *idx);
 
-        if ch == '\n' {
-            *ctx.last_space = None;
-            emit_output(ctx)?;
-            continue;
-        }
-
         if *ctx.col_count >= ctx.width {
             emit_output(ctx)?;
         }

tests/by-util/test_fold.rs

@@ -253,6 +253,18 @@ fn test_zero_width_spaces_in_column_mode() {
         .stdout_is(&input);
 }
 
+#[test]
+fn test_zero_width_after_newline_in_column_mode() {
+    let input = "abc\n\u{200B}From x\n\u{200D}\u{0301}\nb\n";
+    for args in [&[][..], &["-s"]] {
+        new_ucmd!()
+            .args(args)
+            .pipe_in(input)
+            .succeeds()
+            .stdout_is(input);
+    }
+}
+
 #[test]
 fn test_zero_width_spaces_in_character_mode() {
     let len = io_buf_size_times_two();