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LibWeb: Remember when HTML parser should ignore next line feed character

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There's a quirk in HTML where the parser should ignore any line feed
character immediately following a `pre` or `textarea` start tag.

This was working fine when we could peek ahead in the input stream and
see the next token, but didn't work in character-at-a-time parsing with
document.write().

This commit adds the "can ignore next line feed character" as a parser
flag that is maintained across invocations, making it work in this
parsing mode as well.

20 new passes in WPT/html/syntax/parsing/ :^)
This commit is contained in:
Andreas Kling 2025-02-19 16:54:28 +01:00 • committed by Andreas Kling
parent 611833429a
commit 550613e526
Notes: github-actions[bot] 2025-02-20 13:33:19 +00:00
11 changed files with 51 additions and 61 deletions
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39
Libraries/LibWeb/HTML/Parser/HTMLParser.cpp
View file

@ -199,6 +199,13 @@ void HTMLParser::run(HTMLTokenizer::StopAtInsertionPoint stop_at_insertion_point
dbgln_if(HTML_PARSER_DEBUG, "[{}] {}", insertion_mode_name(), token.to_string());
if (m_next_line_feed_can_be_ignored) {
m_next_line_feed_can_be_ignored = false;
if (token.is_character() && token.code_point() == '\n') {
continue;
}
}
// https://html.spec.whatwg.org/multipage/parsing.html#tree-construction-dispatcher
// As each token is emitted from the tokenizer, the user agent must follow the appropriate steps from the following list, known as the tree construction dispatcher:
if (m_stack_of_open_elements.is_empty()
@ -2017,20 +2024,13 @@ void HTMLParser::handle_in_body(HTMLToken& token)
// Insert an HTML element for the token.
(void)insert_html_element(token);
// AD-HOC: We move this step before handling LINE FEED below, to ensure the flag is updated before
// we process the next token. This is necessary due to how we implement token reprocessing.
// Set the frameset-ok flag to "not ok".
m_frameset_ok = false;
// If the next token is a U+000A LINE FEED (LF) character token,
// then ignore that token and move on to the next one.
// (Newlines at the start of pre blocks are ignored as an authoring convenience.)
auto next_token = m_tokenizer.next_token();
if (next_token.has_value() && next_token.value().is_character() && next_token.value().code_point() == '\n') {
// Ignore it.
} else if (next_token.has_value()) {
process_using_the_rules_for(m_insertion_mode, next_token.value());
}
m_next_line_feed_can_be_ignored = true;
// Set the frameset-ok flag to "not ok".
m_frameset_ok = false;
return;
}
@ -2567,16 +2567,14 @@ void HTMLParser::handle_in_body(HTMLToken& token)
// 1. Insert an HTML element for the token.
(void)insert_html_element(token);
// FIXME: 2. If the next token is a U+000A LINE FEED (LF) character token, then ignore that token and move on to the next one. (Newlines at the start of textarea elements are ignored as an authoring convenience.)
// 2. If the next token is a U+000A LINE FEED (LF) character token,
// then ignore that token and move on to the next one.
// (Newlines at the start of textarea elements are ignored as an authoring convenience.)
m_next_line_feed_can_be_ignored = true;
// 3. Switch the tokenizer to the RCDATA state.
m_tokenizer.switch_to({}, HTMLTokenizer::State::RCDATA);
// If the next token is a U+000A LINE FEED (LF) character token,
// then ignore that token and move on to the next one.
// (Newlines at the start of pre blocks are ignored as an authoring convenience.)
auto next_token = m_tokenizer.next_token();
// 4. Let the original insertion mode be the current insertion mode.
m_original_insertion_mode = m_insertion_mode;
@ -2585,13 +2583,6 @@ void HTMLParser::handle_in_body(HTMLToken& token)
// 6. Switch the insertion mode to "text".
m_insertion_mode = InsertionMode::Text;
// FIXME: This step is not in the spec.
if (next_token.has_value() && next_token.value().is_character() && next_token.value().code_point() == '\n') {
// Ignore it.
} else if (next_token.has_value()) {
process_using_the_rules_for(m_insertion_mode, next_token.value());
}
return;
}