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LibWeb/CSS: Insert required comments when serializing lists of tokens

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Certain pairs of tokens are required to have `/**/` inserted between
them to prevent eg two `<ident>`s getting merged together when
round-tripping.
This commit is contained in:
Sam Atkins 2025-11-04 12:04:49 +00:00 • committed by Jelle Raaijmakers
parent 9ac0966fc6
commit e026c98d64
Notes: github-actions[bot] 2025-11-04 13:07:01 +00:00
2 changed files with 164 additions and 62 deletions
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106
Libraries/LibWeb/CSS/Serialize.cpp
View file

@ -4,9 +4,11 @@
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/GenericShorthands.h>
#include <AK/StringBuilder.h>
#include <AK/Utf8View.h>
#include <LibWeb/CSS/Parser/ComponentValue.h>
#include <LibWeb/CSS/Parser/TokenStream.h>
#include <LibWeb/CSS/Serialize.h>
#include <LibWeb/Infra/Strings.h>
@ -198,11 +200,111 @@ String serialize_a_css_declaration(StringView property, StringView value, Import
return builder.to_string_without_validation();
}
// https://drafts.csswg.org/css-syntax/#serialization
static bool needs_comment_between(Parser::ComponentValue const& first, Parser::ComponentValue const& second)
{
// For any consecutive pair of tokens, if the first token shows up in the row headings of the following table, and
// the second token shows up in the column headings, and there’s a ✗ in the cell denoted by the intersection of the
// chosen row and column, the pair of tokens must be serialized with a comment between them.
//
// If the tokenizer preserves comments, and there were comments originally between the token pair, the preserved
// comment(s) should be used; otherwise, an empty comment (/**/) must be inserted. (Preserved comments may be
// reinserted even if the following tables don’t require a comment between two tokens.)
//
// Single characters in the row and column headings represent a <delim-token> with that value, except for "(",
// which represents a (-token.
//
// │ ident │ function │ url │ bad url │ - │ number │ percentage │ dimension │ CDC │ ( │ * │ %
// ───────────┼───────┼──────────┼─────┼─────────┼───┼────────┼────────────┼───────────┼─────┼───┼───┼───
// ident │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ │
// at-keyword │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ │ │
// hash │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ │ │
// dimension │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ │ │
// # │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ │ │
// - │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ │ │
// number │ ✗ │ ✗ │ ✗ │ ✗ │ │ ✗ │ ✗ │ ✗ │ ✗ │ │ │ ✗
// @ │ ✗ │ ✗ │ ✗ │ ✗ │ ✗ │ │ │ │ ✗ │ │ │
// . │ │ │ │ │ │ ✗ │ ✗ │ ✗ │ │ │ │
// + │ │ │ │ │ │ ✗ │ ✗ │ ✗ │ │ │ │
// / │ │ │ │ │ │ │ │ │ │ │ ✗ │
if (first.is(Parser::Token::Type::Ident)) {
if (second.is_function())
return true;
// NB: ( may also be part of a block.
if (second.is_block() && second.block().is_paren())
return true;
if (!second.is_token())
return false;
if (second.token().type() == Parser::Token::Type::Delim)
return second.is_delim('-') || second.is_delim('(');
return first_is_one_of(second.token().type(),
Parser::Token::Type::Ident, Parser::Token::Type::Url, Parser::Token::Type::BadUrl, Parser::Token::Type::Number, Parser::Token::Type::Percentage, Parser::Token::Type::Dimension, Parser::Token::Type::CDC);
}
if (first.is(Parser::Token::Type::AtKeyword)
|| first.is(Parser::Token::Type::Hash)
|| first.is(Parser::Token::Type::Dimension)
|| first.is_delim('#')
|| first.is_delim('-')) {
if (second.is_function())
return true;
if (!second.is_token())
return false;
if (second.token().type() == Parser::Token::Type::Delim)
return second.token().delim() == '-';
return first_is_one_of(second.token().type(),
Parser::Token::Type::Ident, Parser::Token::Type::Url, Parser::Token::Type::BadUrl, Parser::Token::Type::Number, Parser::Token::Type::Percentage, Parser::Token::Type::Dimension, Parser::Token::Type::CDC);
}
if (first.is(Parser::Token::Type::Number)) {
if (second.is_function())
return true;
if (!second.is_token())
return false;
if (second.token().type() == Parser::Token::Type::Delim)
return second.token().delim() == '%';
return first_is_one_of(second.token().type(),
Parser::Token::Type::Ident, Parser::Token::Type::Url, Parser::Token::Type::BadUrl, Parser::Token::Type::Number, Parser::Token::Type::Percentage, Parser::Token::Type::Dimension, Parser::Token::Type::CDC);
}
if (first.is_delim('@')) {
if (second.is_function())
return true;
if (!second.is_token())
return false;
if (second.token().type() == Parser::Token::Type::Delim)
return second.token().delim() == '-';
return first_is_one_of(second.token().type(),
Parser::Token::Type::Ident, Parser::Token::Type::Url, Parser::Token::Type::BadUrl, Parser::Token::Type::CDC);
}
if (first.is_delim('.') || first.is_delim('+')) {
return second.is(Parser::Token::Type::Number) || second.is(Parser::Token::Type::Percentage) || second.is(Parser::Token::Type::Dimension);
}
if (first.is_delim('/')) {
return second.is_delim('*');
}
return false;
}
// https://drafts.csswg.org/css-syntax/#serialization
String serialize_a_series_of_component_values(ReadonlySpan<Parser::ComponentValue> component_values)
{
// FIXME: There are special rules here where we should insert a comment between certain tokens. Do that!
return MUST(String::join(""sv, component_values));
Parser::TokenStream tokens { component_values };
StringBuilder builder;
while (tokens.has_next_token()) {
auto const& current_token = tokens.consume_a_token();
auto const& next_token = tokens.next_token();
builder.append(current_token.to_string());
if (needs_comment_between(current_token, next_token))
builder.append("/**/"sv);
}
return builder.to_string_without_validation();
}
}