fix: make analysis-stats progress bar Unicode-safe

crates/rust-analyzer/src/cli/progress_report.rs

@@ -65,31 +65,7 @@ impl<'a> ProgressReport<'a> {
     }
 
     fn update_text(&mut self, text: &str) {
-        // Get length of common portion
-        let mut common_prefix_length = 0;
-        let common_length = usize::min(self.text.len(), text.len());
-
-        while common_prefix_length < common_length
-            && text.chars().nth(common_prefix_length).unwrap()
-                == self.text.chars().nth(common_prefix_length).unwrap()
-        {
-            common_prefix_length += 1;
-        }
-
-        // Backtrack to the first differing character
-        let mut output = String::new();
-        output += &'\x08'.to_string().repeat(self.text.len() - common_prefix_length);
-        // Output new suffix, using chars() iter to ensure unicode compatibility
-        output.extend(text.chars().skip(common_prefix_length));
-
-        // If the new text is shorter than the old one: delete overlapping characters
-        if let Some(overlap_count) = self.text.len().checked_sub(text.len())
-            && overlap_count > 0
-        {
-            output += &" ".repeat(overlap_count);
-            output += &"\x08".repeat(overlap_count);
-        }
-
+        let output = render_text_update(&self.text, text);
         let _ = io::stdout().write(output.as_bytes());
         let _ = io::stdout().flush();
         text.clone_into(&mut self.text);
@@ -105,11 +81,86 @@ impl<'a> ProgressReport<'a> {
         }
 
         // Fill all last text to space and return the cursor
-        let spaces = " ".repeat(self.text.len());
-        let backspaces = "\x08".repeat(self.text.len());
+        let len = self.text.chars().count();
+        let spaces = " ".repeat(len);
+        let backspaces = "\x08".repeat(len);
         print!("{backspaces}{spaces}{backspaces}");
         let _ = io::stdout().flush();
 
         self.text = String::new();
     }
 }
+
+fn render_text_update(old: &str, new: &str) -> String {
+    let old_len = old.chars().count();
+    let new_len = new.chars().count();
+
+    // Get length of common portion
+    let mut common_prefix_length = 0;
+    let common_length = usize::min(old_len, new_len);
+
+    while common_prefix_length < common_length
+        && new.chars().nth(common_prefix_length).unwrap()
+            == old.chars().nth(common_prefix_length).unwrap()
+    {
+        common_prefix_length += 1;
+    }
+
+    // Backtrack to the first differing character
+    let mut output = String::new();
+    output += &'\x08'.to_string().repeat(old_len - common_prefix_length);
+    // Output new suffix, using chars() iter to ensure unicode compatibility
+    output.extend(new.chars().skip(common_prefix_length));
+
+    // If the new text is shorter than the old one: delete overlapping characters
+    if let Some(overlap_count) = old_len.checked_sub(new_len)
+        && overlap_count > 0
+    {
+        output += &" ".repeat(overlap_count);
+        output += &"\x08".repeat(overlap_count);
+    }
+
+    output
+}
+
+#[cfg(test)]
+mod tests {
+    use super::render_text_update;
+
+    #[test]
+    fn ascii_prefix_reuse() {
+        let old = "1/7 14% processing: foo";
+        let new = "1/7 28% processing: bar";
+        let update = render_text_update(old, new);
+
+        let common = "1/7 ";
+        let backspaces = old.chars().count() - common.chars().count();
+        let expected = format!("{}{}", "\x08".repeat(backspaces), "28% processing: bar");
+        assert_eq!(update, expected);
+    }
+
+    #[test]
+    fn unicode_identifiers_do_not_panic() {
+        // Regression test for rust-lang/rust-analyzer#22844: previous code
+        // compared byte lengths with char indices, so `chars().nth(...).unwrap()`
+        // panicked on non-ASCII.
+        let old = "1/7 14% processing: f::消息";
+        let new = "2/7 28% processing: f::消息内容";
+        let update = render_text_update(old, new);
+
+        let backspaces = old.chars().count();
+        let expected = format!("{}{new}", "\x08".repeat(backspaces));
+        assert_eq!(update, expected);
+    }
+
+    #[test]
+    fn shorter_unicode_message_clears_overlap() {
+        let old = "processing: 消息内容";
+        let new = "processing: 消息";
+        let update = render_text_update(old, new);
+
+        // Drop the last two chars, then blank/backspace the leftover width.
+        let expected = "\x08\x08  \x08\x08";
+        assert_eq!(update, expected);
+    }
+}