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LibWeb/CSS: Bring TokenStream in line with spec

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When the TokenStream code was originally written, there was no such
concept in the CSS Syntax spec. But since then, it's been officially
added, (https://drafts.csswg.org/css-syntax/#css-token-stream) and the
parsing algorithms are described in terms of it. This patch brings our
implementation in line with the spec. A few deprecated TokenStream
methods are left around until their users are also updated to match the
newer spec.

There are a few differences:

- They name things differently. The main confusing one is we had
  `next_token()` which consumed a token and returned it, but the spec
  has a `next_token()` which peeks the next token. The spec names are
  honestly better than what I'd come up with. (`discard_a_token()` is a
  nice addition too!)

- We used to store the index of the token that was just consumed, and
  they instead store the index of the token that will be consumed next.
  This is a perfect breeding ground for off-by-one errors, so I've
  finally added a test suite for TokenStream itself.

- We use a transaction system for rewinding, and the spec uses a stack
  of "marks", which can be manually rewound to. These should be able to
  coexist as long as we stick with marks in the parser spec algorithms,
  and stick with transactions elsewhere.
This commit is contained in:
Sam Atkins 2024-10-09 12:29:29 +01:00 • committed by Sam Atkins
commit b645e26e9b
Notes: github-actions[bot] 2024-10-09 16:30:23 +00:00
8 changed files with 763 additions and 603 deletions
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122
Userland/Libraries/LibWeb/CSS/Parser/MediaParsing.cpp
View file

@ -29,7 +29,7 @@ Vector<NonnullRefPtr<MediaQuery>> Parser::parse_a_media_query_list(TokenStream<T
// AD-HOC: Ignore whitespace-only queries
// to make `@media {..}` equivalent to `@media all {..}`
tokens.skip_whitespace();
tokens.discard_whitespace();
if (!tokens.has_next_token())
return {};
@ -64,8 +64,8 @@ NonnullRefPtr<MediaQuery> Parser::parse_media_query(TokenStream<ComponentValue>&
// `[ not | only ]?`, Returns whether to negate the query
auto parse_initial_modifier = [](auto& tokens) -> Optional<bool> {
auto transaction = tokens.begin_transaction();
tokens.skip_whitespace();
auto& token = tokens.next_token();
tokens.discard_whitespace();
auto& token = tokens.consume_a_token();
if (!token.is(Token::Type::Ident))
return {};
@ -92,11 +92,11 @@ NonnullRefPtr<MediaQuery> Parser::parse_media_query(TokenStream<ComponentValue>&
};
auto media_query = MediaQuery::create();
tokens.skip_whitespace();
tokens.discard_whitespace();
// `<media-condition>`
if (auto media_condition = parse_media_condition(tokens, MediaCondition::AllowOr::Yes)) {
tokens.skip_whitespace();
tokens.discard_whitespace();
if (tokens.has_next_token())
return invalid_media_query();
media_query->m_media_condition = move(media_condition);
@ -106,13 +106,13 @@ NonnullRefPtr<MediaQuery> Parser::parse_media_query(TokenStream<ComponentValue>&
// `[ not | only ]?`
if (auto modifier = parse_initial_modifier(tokens); modifier.has_value()) {
media_query->m_negated = modifier.value();
tokens.skip_whitespace();
tokens.discard_whitespace();
}
// `<media-type>`
if (auto media_type = parse_media_type(tokens); media_type.has_value()) {
media_query->m_media_type = media_type.value();
tokens.skip_whitespace();
tokens.discard_whitespace();
} else {
return invalid_media_query();
}
@ -121,9 +121,9 @@ NonnullRefPtr<MediaQuery> Parser::parse_media_query(TokenStream<ComponentValue>&
return media_query;
// `[ and <media-condition-without-or> ]?`
if (auto maybe_and = tokens.next_token(); maybe_and.is_ident("and"sv)) {
if (auto maybe_and = tokens.consume_a_token(); maybe_and.is_ident("and"sv)) {
if (auto media_condition = parse_media_condition(tokens, MediaCondition::AllowOr::No)) {
tokens.skip_whitespace();
tokens.discard_whitespace();
if (tokens.has_next_token())
return invalid_media_query();
media_query->m_media_condition = move(media_condition);
@ -142,14 +142,14 @@ OwnPtr<MediaCondition> Parser::parse_media_condition(TokenStream<ComponentValue>
{
// `<media-not> | <media-in-parens> [ <media-and>* | <media-or>* ]`
auto transaction = tokens.begin_transaction();
tokens.skip_whitespace();
tokens.discard_whitespace();
// `<media-not> = not <media-in-parens>`
auto parse_media_not = [&](auto& tokens) -> OwnPtr<MediaCondition> {
auto local_transaction = tokens.begin_transaction();
tokens.skip_whitespace();
tokens.discard_whitespace();
auto& first_token = tokens.next_token();
auto& first_token = tokens.consume_a_token();
if (first_token.is_ident("not"sv)) {
if (auto child_condition = parse_media_condition(tokens, MediaCondition::AllowOr::Yes)) {
local_transaction.commit();
@ -162,11 +162,11 @@ OwnPtr<MediaCondition> Parser::parse_media_condition(TokenStream<ComponentValue>
auto parse_media_with_combinator = [&](auto& tokens, StringView combinator) -> OwnPtr<MediaCondition> {
auto local_transaction = tokens.begin_transaction();
tokens.skip_whitespace();
tokens.discard_whitespace();
auto& first = tokens.next_token();
auto& first = tokens.consume_a_token();
if (first.is_ident(combinator)) {
tokens.skip_whitespace();
tokens.discard_whitespace();
if (auto media_in_parens = parse_media_in_parens(tokens)) {
local_transaction.commit();
return media_in_parens;
@ -189,7 +189,7 @@ OwnPtr<MediaCondition> Parser::parse_media_condition(TokenStream<ComponentValue>
// `<media-in-parens> [ <media-and>* | <media-or>* ]`
if (auto maybe_media_in_parens = parse_media_in_parens(tokens)) {
tokens.skip_whitespace();
tokens.discard_whitespace();
// Only `<media-in-parens>`
if (!tokens.has_next_token()) {
transaction.commit();
@ -203,11 +203,11 @@ OwnPtr<MediaCondition> Parser::parse_media_condition(TokenStream<ComponentValue>
if (auto media_and = parse_media_and(tokens)) {
child_conditions.append(media_and.release_nonnull());
tokens.skip_whitespace();
tokens.discard_whitespace();
while (tokens.has_next_token()) {
if (auto next_media_and = parse_media_and(tokens)) {
child_conditions.append(next_media_and.release_nonnull());
tokens.skip_whitespace();
tokens.discard_whitespace();
continue;
}
// We failed - invalid syntax!
@ -223,11 +223,11 @@ OwnPtr<MediaCondition> Parser::parse_media_condition(TokenStream<ComponentValue>
if (auto media_or = parse_media_or(tokens)) {
child_conditions.append(media_or.release_nonnull());
tokens.skip_whitespace();
tokens.discard_whitespace();
while (tokens.has_next_token()) {
if (auto next_media_or = parse_media_or(tokens)) {
child_conditions.append(next_media_or.release_nonnull());
tokens.skip_whitespace();
tokens.discard_whitespace();
continue;
}
// We failed - invalid syntax!
@ -247,7 +247,7 @@ OwnPtr<MediaCondition> Parser::parse_media_condition(TokenStream<ComponentValue>
Optional<MediaFeature> Parser::parse_media_feature(TokenStream<ComponentValue>& tokens)
{
// `[ <mf-plain> | <mf-boolean> | <mf-range> ]`
tokens.skip_whitespace();
tokens.discard_whitespace();
// `<mf-name> = <ident>`
struct MediaFeatureName {
@ -260,7 +260,7 @@ Optional<MediaFeature> Parser::parse_media_feature(TokenStream<ComponentValue>&
};
auto parse_mf_name = [](auto& tokens, bool allow_min_max_prefix) -> Optional<MediaFeatureName> {
auto transaction = tokens.begin_transaction();
auto& token = tokens.next_token();
auto& token = tokens.consume_a_token();
if (token.is(Token::Type::Ident)) {
auto name = token.token().ident();
if (auto id = media_feature_id_from_string(name); id.has_value()) {
@ -285,10 +285,10 @@ Optional<MediaFeature> Parser::parse_media_feature(TokenStream<ComponentValue>&
// `<mf-boolean> = <mf-name>`
auto parse_mf_boolean = [&](auto& tokens) -> Optional<MediaFeature> {
auto transaction = tokens.begin_transaction();
tokens.skip_whitespace();
tokens.discard_whitespace();
if (auto maybe_name = parse_mf_name(tokens, false); maybe_name.has_value()) {
tokens.skip_whitespace();
tokens.discard_whitespace();
if (!tokens.has_next_token()) {
transaction.commit();
return MediaFeature::boolean(maybe_name->id);
@ -301,14 +301,14 @@ Optional<MediaFeature> Parser::parse_media_feature(TokenStream<ComponentValue>&
// `<mf-plain> = <mf-name> : <mf-value>`
auto parse_mf_plain = [&](auto& tokens) -> Optional<MediaFeature> {
auto transaction = tokens.begin_transaction();
tokens.skip_whitespace();
tokens.discard_whitespace();
if (auto maybe_name = parse_mf_name(tokens, true); maybe_name.has_value()) {
tokens.skip_whitespace();
if (tokens.next_token().is(Token::Type::Colon)) {
tokens.skip_whitespace();
tokens.discard_whitespace();
if (tokens.consume_a_token().is(Token::Type::Colon)) {
tokens.discard_whitespace();
if (auto maybe_value = parse_media_feature_value(maybe_name->id, tokens); maybe_value.has_value()) {
tokens.skip_whitespace();
tokens.discard_whitespace();
if (!tokens.has_next_token()) {
transaction.commit();
switch (maybe_name->type) {
@ -333,9 +333,9 @@ Optional<MediaFeature> Parser::parse_media_feature(TokenStream<ComponentValue>&
// <mf-comparison> = <mf-lt> | <mf-gt> | <mf-eq>`
auto parse_comparison = [](auto& tokens) -> Optional<MediaFeature::Comparison> {
auto transaction = tokens.begin_transaction();
tokens.skip_whitespace();
tokens.discard_whitespace();
auto& first = tokens.next_token();
auto& first = tokens.consume_a_token();
if (first.is(Token::Type::Delim)) {
auto first_delim = first.token().delim();
if (first_delim == '=') {
@ -343,9 +343,9 @@ Optional<MediaFeature> Parser::parse_media_feature(TokenStream<ComponentValue>&
return MediaFeature::Comparison::Equal;
}
if (first_delim == '<') {
auto& second = tokens.peek_token();
auto& second = tokens.next_token();
if (second.is_delim('=')) {
tokens.next_token();
tokens.discard_a_token();
transaction.commit();
return MediaFeature::Comparison::LessThanOrEqual;
}
@ -353,9 +353,9 @@ Optional<MediaFeature> Parser::parse_media_feature(TokenStream<ComponentValue>&
return MediaFeature::Comparison::LessThan;
}
if (first_delim == '>') {
auto& second = tokens.peek_token();
auto& second = tokens.next_token();
if (second.is_delim('=')) {
tokens.next_token();
tokens.discard_a_token();
transaction.commit();
return MediaFeature::Comparison::GreaterThanOrEqual;
}
@ -403,16 +403,16 @@ Optional<MediaFeature> Parser::parse_media_feature(TokenStream<ComponentValue>&
// | <mf-value> <mf-gt> <mf-name> <mf-gt> <mf-value>`
auto parse_mf_range = [&](auto& tokens) -> Optional<MediaFeature> {
auto transaction = tokens.begin_transaction();
tokens.skip_whitespace();
tokens.discard_whitespace();
// `<mf-name> <mf-comparison> <mf-value>`
// NOTE: We have to check for <mf-name> first, since all <mf-name>s will also parse as <mf-value>.
if (auto maybe_name = parse_mf_name(tokens, false); maybe_name.has_value() && media_feature_type_is_range(maybe_name->id)) {
tokens.skip_whitespace();
tokens.discard_whitespace();
if (auto maybe_comparison = parse_comparison(tokens); maybe_comparison.has_value()) {
tokens.skip_whitespace();
tokens.discard_whitespace();
if (auto maybe_value = parse_media_feature_value(maybe_name->id, tokens); maybe_value.has_value()) {
tokens.skip_whitespace();
tokens.discard_whitespace();
if (!tokens.has_next_token() && !maybe_value->is_ident()) {
transaction.commit();
return MediaFeature::half_range(maybe_value.release_value(), flip(maybe_comparison.release_value()), maybe_name->id);
@ -435,23 +435,23 @@ Optional<MediaFeature> Parser::parse_media_feature(TokenStream<ComponentValue>&
while (tokens.has_next_token() && !maybe_name.has_value()) {
if (auto maybe_comparison = parse_comparison(tokens); maybe_comparison.has_value()) {
// We found a comparison, so the next non-whitespace token should be the <mf-name>
tokens.skip_whitespace();
tokens.discard_whitespace();
maybe_name = parse_mf_name(tokens, false);
break;
}
tokens.next_token();
tokens.skip_whitespace();
tokens.discard_a_token();
tokens.discard_whitespace();
}
}
// Now, we can parse the range properly.
if (maybe_name.has_value() && media_feature_type_is_range(maybe_name->id)) {
if (auto maybe_left_value = parse_media_feature_value(maybe_name->id, tokens); maybe_left_value.has_value()) {
tokens.skip_whitespace();
tokens.discard_whitespace();
if (auto maybe_left_comparison = parse_comparison(tokens); maybe_left_comparison.has_value()) {
tokens.skip_whitespace();
tokens.next_token(); // The <mf-name> which we already parsed above.
tokens.skip_whitespace();
tokens.discard_whitespace();
tokens.discard_a_token(); // The <mf-name> which we already parsed above.
tokens.discard_whitespace();
if (!tokens.has_next_token()) {
transaction.commit();
@ -459,9 +459,9 @@ Optional<MediaFeature> Parser::parse_media_feature(TokenStream<ComponentValue>&
}
if (auto maybe_right_comparison = parse_comparison(tokens); maybe_right_comparison.has_value()) {
tokens.skip_whitespace();
tokens.discard_whitespace();
if (auto maybe_right_value = parse_media_feature_value(maybe_name->id, tokens); maybe_right_value.has_value()) {
tokens.skip_whitespace();
tokens.discard_whitespace();
// For this to be valid, the following must be true:
// - Comparisons must either both be >/>= or both be </<=.
// - Neither comparison can be `=`.
@ -500,8 +500,8 @@ Optional<MediaFeature> Parser::parse_media_feature(TokenStream<ComponentValue>&
Optional<MediaQuery::MediaType> Parser::parse_media_type(TokenStream<ComponentValue>& tokens)
{
auto transaction = tokens.begin_transaction();
tokens.skip_whitespace();
auto const& token = tokens.next_token();
tokens.discard_whitespace();
auto const& token = tokens.consume_a_token();
if (!token.is(Token::Type::Ident))
return {};
@ -517,19 +517,19 @@ OwnPtr<MediaCondition> Parser::parse_media_in_parens(TokenStream<ComponentValue>
{
// `<media-in-parens> = ( <media-condition> ) | ( <media-feature> ) | <general-enclosed>`
auto transaction = tokens.begin_transaction();
tokens.skip_whitespace();
tokens.discard_whitespace();
// `( <media-condition> ) | ( <media-feature> )`
auto const& first_token = tokens.peek_token();
auto const& first_token = tokens.next_token();
if (first_token.is_block() && first_token.block().is_paren()) {
TokenStream inner_token_stream { first_token.block().values() };
if (auto maybe_media_condition = parse_media_condition(inner_token_stream, MediaCondition::AllowOr::Yes)) {
tokens.next_token();
tokens.discard_a_token();
transaction.commit();
return maybe_media_condition.release_nonnull();
}
if (auto maybe_media_feature = parse_media_feature(inner_token_stream); maybe_media_feature.has_value()) {
tokens.next_token();
tokens.discard_a_token();
transaction.commit();
return MediaCondition::from_feature(maybe_media_feature.release_value());
}
@ -553,10 +553,10 @@ Optional<MediaFeatureValue> Parser::parse_media_feature_value(MediaFeatureID med
// NOTE: Calculations are not allowed for media feature values, at least in the current spec, so we reject them.
// Identifiers
if (tokens.peek_token().is(Token::Type::Ident)) {
if (tokens.next_token().is(Token::Type::Ident)) {
auto transaction = tokens.begin_transaction();
tokens.skip_whitespace();
auto keyword = keyword_from_string(tokens.next_token().token().ident());
tokens.discard_whitespace();
auto keyword = keyword_from_string(tokens.consume_a_token().token().ident());
if (keyword.has_value() && media_feature_accepts_keyword(media_feature, keyword.value())) {
transaction.commit();
return MediaFeatureValue(keyword.value());
@ -568,7 +568,7 @@ Optional<MediaFeatureValue> Parser::parse_media_feature_value(MediaFeatureID med
// Boolean (<mq-boolean> in the spec: a 1 or 0)
if (media_feature_accepts_type(media_feature, MediaFeatureValueType::Boolean)) {
auto transaction = tokens.begin_transaction();
tokens.skip_whitespace();
tokens.discard_whitespace();
if (auto integer = parse_integer(tokens); integer.has_value() && !integer->is_calculated()) {
auto integer_value = integer->value();
if (integer_value == 0 || integer_value == 1) {
@ -590,7 +590,7 @@ Optional<MediaFeatureValue> Parser::parse_media_feature_value(MediaFeatureID med
// Length
if (media_feature_accepts_type(media_feature, MediaFeatureValueType::Length)) {
auto transaction = tokens.begin_transaction();
tokens.skip_whitespace();
tokens.discard_whitespace();
if (auto length = parse_length(tokens); length.has_value() && !length->is_calculated()) {
transaction.commit();
return MediaFeatureValue(length->value());
@ -600,7 +600,7 @@ Optional<MediaFeatureValue> Parser::parse_media_feature_value(MediaFeatureID med
// Ratio
if (media_feature_accepts_type(media_feature, MediaFeatureValueType::Ratio)) {
auto transaction = tokens.begin_transaction();
tokens.skip_whitespace();
tokens.discard_whitespace();
if (auto ratio = parse_ratio(tokens); ratio.has_value()) {
transaction.commit();
return MediaFeatureValue(ratio.release_value());
@ -610,7 +610,7 @@ Optional<MediaFeatureValue> Parser::parse_media_feature_value(MediaFeatureID med
// Resolution
if (media_feature_accepts_type(media_feature, MediaFeatureValueType::Resolution)) {
auto transaction = tokens.begin_transaction();
tokens.skip_whitespace();
tokens.discard_whitespace();
if (auto resolution = parse_resolution(tokens); resolution.has_value() && !resolution->is_calculated()) {
transaction.commit();
return MediaFeatureValue(resolution->value());