swc-project/swc · warning · Error

Non-space character in "frameset"

Error message

Non-space character in "frameset"

What it means

A non-whitespace character token was dispatched in the 'in frameset' insertion mode. The spec says: parse error, ignore the token — frameset content cannot hold text, so the character is dropped from the tree. NonSpaceCharacterInFrameset records the loss with the character's span.

Source

Thrown at crates/swc_html_parser/src/parser/mod.rs:6433

                                self.errors.push(Error::new(
                                    token_and_info.span,
                                    ErrorKind::EofWithUnclosedElements,
                                ));
                            }
                            _ => {}
                        }

                        self.stopped = true;
                    }
                    // Anything else
                    //
                    // Parse error. Ignore the token.
                    _ => match token {
                        // Doctype handled above
                        // Comment handled above
                        // EOF handled above
                        Token::Character { .. } => {
                            self.errors.push(Error::new(
                                token_and_info.span,
                                ErrorKind::NonSpaceCharacterInFrameset,
                            ));
                        }
                        Token::StartTag { tag_name, .. } => {
                            self.errors.push(Error::new(
                                token_and_info.span,
                                ErrorKind::StrayStartTag(tag_name.clone()),
                            ));
                        }
                        Token::EndTag { tag_name, .. } => {
                            self.errors.push(Error::new(
                                token_and_info.span,
                                ErrorKind::StrayEndTag(tag_name.clone()),
                            ));
                        }
                        _ => {
                            unreachable!()

View on GitHub (pinned to 5176682b65)

Solutions

  1. Wrap fallback text in <noframes>...</noframes> (or a <frame src> document).
  2. Remove stray text nodes from the frameset region entirely.
  3. If the input is third-party, filter ErrorKind::NonSpaceCharacterInFrameset; note the text is dropped, not relocated.

Example fix

<!-- before -->
<frameset cols="*">
  Please enable frames.
  <frame src="a.html">
</frameset>

<!-- after -->
<frameset cols="*">
  <frame src="a.html">
  <noframes>Please enable frames.</noframes>
</frameset>
Defensive patterns

Strategy: validation

Validate before calling

// Heuristic: text (not wrapped in <noframes>) inside the frameset region.
fn has_bare_text_in_frameset(src: &str) -> bool {
    let lower = src.to_ascii_lowercase();
    if let (Some(s), Some(e)) = (lower.find("<frameset"), lower.find("</frameset>")) {
        if e > s {
            let region = &src[s..e];
            // crude: strip tags, see if visible text remains
            let mut text = String::new();
            let mut in_tag = false;
            for c in region.chars() {
                match c { '<' => in_tag = true, '>' => in_tag = false, _ if !in_tag => text.push(c), _ => {} }
            }
            return text.chars().any(|c| !c.is_ascii_whitespace());
        }
    }
    false
}

Type guard

use swc_html_parser::error::{Error, ErrorKind};

fn is_non_space_in_frameset(err: &Error) -> bool {
    matches!(err.kind(), ErrorKind::NonSpaceCharacterInFrameset)
}

Try / catch

let mut errors = Vec::new();
let doc = parse_file_as_document(&fm, config, &mut errors)?;
if errors.iter().any(is_non_space_in_frameset) {
    log::warn!("text inside <frameset> was dropped; use <noframes>");
}

Prevention

When it happens

Trigger: Visible text between frameset tags, e.g. `<frameset rows="*">Your browser does not support frames</frameset>` (text directly, not inside <noframes>). The 'anything else' arm of InFrameset mode pushes the error.

Common situations: Fallback messages intended for non-frame browsers written directly into the frameset instead of inside <noframes>; copy-pasting body-style content into frameset layouts; legacy migration errors.

Related errors

AI-assisted analysis of swc-project/swc@5176682b65 (2026-08-17). Data as JSON: /api/errors/344a1d0a180affd4. Report an issue: GitHub.