micha's suggestion for normalize_whitespace

ntBre · ntBre · commit 1c764d11e276 · 2026-03-24T15:24:57.000-04:00
diff --git a/crates/ruff_annotate_snippets/src/renderer/display_list.rs b/crates/ruff_annotate_snippets/src/renderer/display_list.rs
@@ -1849,36 +1849,42 @@ fn is_annotation_empty(annotation: &Annotation<'_>) -> bool {
         .all(|fragment| fragment.content.is_empty())
 }
 
-// We replace some characters so the CLI output is always consistent and underlines aligned.
-const OUTPUT_REPLACEMENTS: &[(char, &str)] = &[
-    ('\t', "    "),   // We do our own tab replacement
-    ('\u{200D}', ""), // Replace ZWJ with nothing for consistent terminal output of grapheme clusters.
-    ('\u{202A}', ""), // The following unicode text flow control characters are inconsistently
-    ('\u{202B}', ""), // supported across CLIs and can cause confusion due to the bytes on disk
-    ('\u{202D}', ""), // not corresponding to the visible source code, so we replace them always.
-    ('\u{202E}', ""),
-    ('\u{2066}', ""),
-    ('\u{2067}', ""),
-    ('\u{2068}', ""),
-    ('\u{202C}', ""),
-    ('\u{2069}', ""),
-];
-
 fn normalize_whitespace(str: &str) -> Cow<'_, str> {
-    // This is an optimization to avoid repeated `str::replace` calls in the typical case of no
-    // valid replacements. Note that this list needs to be kept in sync with `OUTPUT_REPLACEMENTS`.
-    if !str.contains([
-        '\t', '\u{200d}', '\u{202a}', '\u{202b}', '\u{202d}', '\u{202e}', '\u{2066}', '\u{2067}',
-        '\u{2068}', '\u{202c}', '\u{2069}',
-    ]) {
-        return Cow::Borrowed(str);
+    let mut output = String::new();
+    let mut last_index = 0usize;
+
+    // We replace some characters so the CLI output is always consistent and underlines aligned.
+    for (index, c) in str.char_indices() {
+        let replacement = match c {
+            '\t' => "    ",   // We do our own tab replacement
+            '\u{200D}' => "", // Replace ZWJ with nothing for consistent terminal output of grapheme clusters.
+            '\u{202A}' => "", // The following unicode text flow control characters are inconsistently
+            '\u{202B}' => "", // supported across CLIs and can cause confusion due to the bytes on disk
+            '\u{202D}' => "", // not corresponding to the visible source code, so we replace them always.
+            '\u{202E}' => "",
+            '\u{2066}' => "",
+            '\u{2067}' => "",
+            '\u{2068}' => "",
+            '\u{202C}' => "",
+            '\u{2069}' => "",
+            _ => continue,
+        };
+
+        if output.is_empty() {
+            output.reserve(str.len());
+        }
+
+        output.push_str(&str[last_index..index]);
+        output.push_str(replacement);
+        last_index = index + c.len_utf8();
     }
 
-    let mut s = str.to_owned();
-    for (c, replacement) in OUTPUT_REPLACEMENTS {
-        s = s.replace(*c, replacement);
+    if output.is_empty() {
+        Cow::Borrowed(str)
+    } else {
+        output.push_str(&str[last_index..]);
+        Cow::Owned(output)
     }
-    Cow::Owned(s)
 }
 
 fn overlaps(
