servo/components/style/parser.rs

/* 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 http://mozilla.org/MPL/2.0/. */

//! The context within which CSS code is parsed.

use context::QuirksMode;
use cssparser::{Parser, SourceLocation, UnicodeRange};
use error_reporting::{ParseErrorReporter, ContextualParseError};
use style_traits::{OneOrMoreSeparated, ParseError, ParsingMode, Separator};
#[cfg(feature = "gecko")]
use style_traits::{PARSING_MODE_DEFAULT, PARSING_MODE_ALLOW_UNITLESS_LENGTH, PARSING_MODE_ALLOW_ALL_NUMERIC_VALUES};
use stylesheets::{CssRuleType, Origin, UrlExtraData, Namespaces};

/// Asserts that all ParsingMode flags have a matching ParsingMode value in gecko.
#[cfg(feature = "gecko")]
#[inline]
pub fn assert_parsing_mode_match() {
    use gecko_bindings::structs;

    macro_rules! check_parsing_modes {
        ( $( $a:ident => $b:ident ),*, ) => {
            if cfg!(debug_assertions) {
                let mut modes = ParsingMode::all();
                $(
                    assert_eq!(structs::$a as usize, $b.bits() as usize, stringify!($b));
                    modes.remove($b);
                )*
                assert_eq!(modes, ParsingMode::empty(), "all ParsingMode bits should have an assertion");
            }
        }
    }

    check_parsing_modes! {
        ParsingMode_Default => PARSING_MODE_DEFAULT,
        ParsingMode_AllowUnitlessLength => PARSING_MODE_ALLOW_UNITLESS_LENGTH,
        ParsingMode_AllowAllNumericValues => PARSING_MODE_ALLOW_ALL_NUMERIC_VALUES,
    }
}

/// The context required to report a parse error.
pub struct ParserErrorContext<'a, R: 'a> {
    /// An error reporter to report syntax errors.
    pub error_reporter: &'a R,
}

/// 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 type, if any.
    pub rule_type: Option<CssRuleType>,
    /// The mode to use when parsing.
    pub parsing_mode: ParsingMode,
    /// The quirks mode of this stylesheet.
    pub quirks_mode: QuirksMode,
    /// The currently active namespaces.
    pub namespaces: Option<&'a Namespaces>,
}

impl<'a> ParserContext<'a> {
    /// Create a parser context.
    pub fn new(
        stylesheet_origin: Origin,
        url_data: &'a UrlExtraData,
        rule_type: Option<CssRuleType>,
        parsing_mode: ParsingMode,
        quirks_mode: QuirksMode,
    ) -> ParserContext<'a> {
        ParserContext {
            stylesheet_origin: stylesheet_origin,
            url_data: url_data,
            rule_type: rule_type,
            parsing_mode: parsing_mode,
            quirks_mode: quirks_mode,
            namespaces: None,
        }
    }

    /// Create a parser context for on-the-fly parsing in CSSOM
    pub fn new_for_cssom(
        url_data: &'a UrlExtraData,
        rule_type: Option<CssRuleType>,
        parsing_mode: ParsingMode,
        quirks_mode: QuirksMode
    ) -> ParserContext<'a> {
        Self::new(
            Origin::Author,
            url_data,
            rule_type,
            parsing_mode,
            quirks_mode,
        )
    }

    /// Create a parser context based on a previous context, but with a modified rule type.
    pub fn new_with_rule_type(
        context: &'a ParserContext,
        rule_type: CssRuleType,
        namespaces: &'a Namespaces,
    ) -> ParserContext<'a> {
        ParserContext {
            stylesheet_origin: context.stylesheet_origin,
            url_data: context.url_data,
            rule_type: Some(rule_type),
            parsing_mode: context.parsing_mode,
            quirks_mode: context.quirks_mode,
            namespaces: Some(namespaces),
        }
    }

    /// Get the rule type, which assumes that one is available.
    pub fn rule_type(&self) -> CssRuleType {
        self.rule_type.expect("Rule type expected, but none was found.")
    }

    /// Record a CSS parse error with this context’s error reporting.
    pub fn log_css_error<R>(&self,
                            context: &ParserErrorContext<R>,
                            location: SourceLocation,
                            error: ContextualParseError)
        where R: ParseErrorReporter
    {
        let location = SourceLocation {
            line: location.line,
            column: location.column,
        };
        context.error_reporter.report_error(self.url_data, location, error)
    }
}

// XXXManishearth Replace all specified value parse impls with impls of this
// trait. This will make it easy to write more generic values in the future.
/// A trait to abstract parsing of a specified value given a `ParserContext` and
/// CSS input.
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 Parse for UnicodeRange {
    fn parse<'i, 't>(_context: &ParserContext, input: &mut Parser<'i, 't>)
                     -> Result<Self, ParseError<'i>> {
        UnicodeRange::parse(input).map_err(|e| e.into())
    }
}