1 files changed, 178 insertions, 0 deletions
diff --git a/servo/components/style/parser.rs b/servo/components/style/parser.rs
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! The context within which CSS code is parsed.
+
+use crate::context::QuirksMode;
+use crate::error_reporting::{ContextualParseError, ParseErrorReporter};
+use crate::stylesheets::{CssRuleType, CssRuleTypes, Namespaces, Origin, UrlExtraData};
+use crate::use_counters::UseCounters;
+use cssparser::{Parser, SourceLocation, UnicodeRange};
+use std::borrow::Cow;
+use style_traits::{OneOrMoreSeparated, ParseError, ParsingMode, Separator};
+
+/// The data that the parser needs from outside in order to parse a stylesheet.
+pub struct ParserContext<'a> {
+    /// The `Origin` of the stylesheet, whether it's a user, author or
+    /// user-agent stylesheet.
+    pub stylesheet_origin: Origin,
+    /// The extra data we need for resolving url values.
+    pub url_data: &'a UrlExtraData,
+    /// The current rule types, if any.
+    pub rule_types: CssRuleTypes,
+    /// The mode to use when parsing.
+    pub parsing_mode: ParsingMode,
+    /// The quirks mode of this stylesheet.
+    pub quirks_mode: QuirksMode,
+    /// The active error reporter, or none if error reporting is disabled.
+    error_reporter: Option<&'a dyn ParseErrorReporter>,
+    /// The currently active namespaces.
+    pub namespaces: Cow<'a, Namespaces>,
+    /// The use counters we want to record while parsing style rules, if any.
+    pub use_counters: Option<&'a UseCounters>,
+}
+
+impl<'a> ParserContext<'a> {
+    /// Create a parser context.
+    #[inline]
+    pub fn new(
+        stylesheet_origin: Origin,
+        url_data: &'a UrlExtraData,
+        rule_type: Option<CssRuleType>,
+        parsing_mode: ParsingMode,
+        quirks_mode: QuirksMode,
+        namespaces: Cow<'a, Namespaces>,
+        error_reporter: Option<&'a dyn ParseErrorReporter>,
+        use_counters: Option<&'a UseCounters>,
+    ) -> Self {
+        Self {
+            stylesheet_origin,
+            url_data,
+            rule_types: rule_type.map(CssRuleTypes::from).unwrap_or_default(),
+            parsing_mode,
+            quirks_mode,
+            error_reporter,
+            namespaces,
+            use_counters,
+        }
+    }
+
+    /// Temporarily sets the rule_type and executes the callback function, returning its result.
+    pub fn nest_for_rule<R>(
+        &mut self,
+        rule_type: CssRuleType,
+        cb: impl FnOnce(&mut Self) -> R,
+    ) -> R {
+        let old_rule_types = self.rule_types;
+        self.rule_types.insert(rule_type);
+        let r = cb(self);
+        self.rule_types = old_rule_types;
+        r
+    }
+
+    /// Whether we're in a @page rule.
+    #[inline]
+    pub fn in_page_rule(&self) -> bool {
+        self.rule_types.contains(CssRuleType::Page)
+    }
+
+    /// Get the rule type, which assumes that one is available.
+    pub fn rule_types(&self) -> CssRuleTypes {
+        self.rule_types
+    }
+
+    /// Returns whether CSS error reporting is enabled.
+    #[inline]
+    pub fn error_reporting_enabled(&self) -> bool {
+        self.error_reporter.is_some()
+    }
+
+    /// Record a CSS parse error with this context’s error reporting.
+    pub fn log_css_error(&self, location: SourceLocation, error: ContextualParseError) {
+        let error_reporter = match self.error_reporter {
+            Some(r) => r,
+            None => return,
+        };
+
+        error_reporter.report_error(self.url_data, location, error)
+    }
+
+    /// Whether we're in a user-agent stylesheet.
+    #[inline]
+    pub fn in_ua_sheet(&self) -> bool {
+        self.stylesheet_origin == Origin::UserAgent
+    }
+
+    /// Returns whether chrome-only rules should be parsed.
+    #[inline]
+    pub fn chrome_rules_enabled(&self) -> bool {
+        self.url_data.chrome_rules_enabled() || self.stylesheet_origin != Origin::Author
+    }
+}
+
+/// A trait to abstract parsing of a specified value given a `ParserContext` and
+/// CSS input.
+///
+/// This can be derived on keywords with `#[derive(Parse)]`.
+///
+/// The derive code understands the following attributes on each of the variants:
+///
+///  * `#[parse(aliases = "foo,bar")]` can be used to alias a value with another
+///    at parse-time.
+///
+///  * `#[parse(condition = "function")]` can be used to make the parsing of the
+///    value conditional on `function`, which needs to fulfill
+///    `fn(&ParserContext) -> bool`.
+pub trait Parse: Sized {
+    /// Parse a value of this type.
+    ///
+    /// Returns an error on failure.
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>>;
+}
+
+impl<T> Parse for Vec<T>
+where
+    T: Parse + OneOrMoreSeparated,
+    <T as OneOrMoreSeparated>::S: Separator,
+{
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        <T as OneOrMoreSeparated>::S::parse(input, |i| T::parse(context, i))
+    }
+}
+
+impl<T> Parse for Box<T>
+where
+    T: Parse,
+{
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        T::parse(context, input).map(Box::new)
+    }
+}
+
+impl Parse for crate::OwnedStr {
+    fn parse<'i, 't>(
+        _: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Ok(input.expect_string()?.as_ref().to_owned().into())
+    }
+}
+
+impl Parse for UnicodeRange {
+    fn parse<'i, 't>(
+        _: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Ok(UnicodeRange::parse(input)?)
+    }
+}