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use super::Parser;
use crate::{
Parse, Syntax,
ast::*,
error::{Error, ErrorKind, PResult},
pos::Span,
tokenizer::{Token, TokenWithSpan},
};
// https://www.w3.org/TR/css-cascade-5/#at-import
//
// @import [ <url> | <string> ]
// [ layer | layer( <layer-name> ) ]?
// <import-conditions> ;
// <import-conditions> = [ supports( [ <supports-condition> | <declaration> ] ) ]?
// <media-query-list>?
impl<'a> Parse<'a> for ImportPrelude<'a> {
fn parse(input: &mut Parser<'a>) -> PResult<Self> {
// The indented syntax accepts an unquoted path (`@import other.css`),
// but an ident glued to `(` is a function href
// (`@import url("theme.css")`), which the `Url::parse` arm handles.
let sass_unquoted_path = input.syntax == Syntax::Sass
&& matches!(input.cursor.peek()?, TokenWithSpan { token: Token::Ident(..), span }
if input.source.as_bytes().get(span.end) != Some(&b'('));
let href = match &input.cursor.peek()?.token {
Token::Str(..) | Token::StrTemplate(..) => input.parse().map(ImportPreludeHref::Str)?,
Token::Ident(..) if sass_unquoted_path => {
let start = input.cursor.peek()?.span.start;
let mut end = start;
while matches!(
&input.cursor.peek()?.token,
Token::Ident(..) | Token::Dot(..) | Token::Minus(..) | Token::Solidus(..)
) && input.cursor.peek()?.span.start == end
{
end = input.cursor.bump()?.span.end;
}
let raw = unsafe { input.source.get_unchecked(start..end) };
let span = Span { start, end };
ImportPreludeHref::Str(InterpolableStr::Literal(Str { value: raw, raw, span }))
}
_ => match input.try_parse(Url::parse) {
Ok(url) => ImportPreludeHref::Url(url),
Err(mut error) => {
// `Url::parse` marks a non-url shape (`@import url;`) with
// the internal `TryParseError`; this is a surfacing site,
// so concretize it first.
if matches!(error.kind, ErrorKind::TryParseError) {
error.kind = ErrorKind::ExpectUrl;
}
// Sass only: the content of `url(...)` may be SassScript
// that is not a parsable URL,
// e.g. `@import url($dir+"/path");`.
// Mirrors the fallback in `parse_component_value_atom`.
if !matches!(input.syntax, Syntax::Scss | Syntax::Sass) {
return Err(error);
}
let (function_name, function_name_span) = input.cursor.expect_ident()?;
let function_name = input.ident(function_name, function_name_span);
if !function_name.name.eq_ignore_ascii_case("url") {
return Err(error);
}
input
.parse_function(InterpolableIdent::Literal(function_name))
.map(ImportPreludeHref::Function)
.map_err(|_| error)?
}
},
};
let mut span = *href.span();
let structured = input.try_parse(Self::parse_structured_tail);
let (layer, supports, media, modifiers) = match structured {
Ok((layer, supports, media)) => (layer, supports, media, None),
// Reference compilers accept arbitrary import modifiers (idents,
// unknown functions, media-ish parens, further comma-chained
// imports); keep the whole tail as raw component values.
// NOTE: Scss/Sass multi-path imports (`@import 'a', 'b';`) never
// get here — the at-rule dispatch claims them as
// `SassImportPrelude` before trying `ImportPrelude`.
Err(_) => {
let start = input.cursor.peek()?.span.start;
let values = input.parse_declaration_value_tokens(true)?;
// A trailing comma has no import after it — reference
// compilers reject that, so don't paper over it.
if let Some(ComponentValue::TokenWithSpan(TokenWithSpan {
token: Token::Comma(..),
span,
})) = values.last()
{
return Err(Error { kind: ErrorKind::ExpectRule, span: *span });
}
let end = values.last().map_or(start, |value| value.span().end);
(None, None, None, Some(ComponentValues { values, span: Span { start, end } }))
}
};
if let Some(layer) = &layer {
span.end = layer.span().end;
}
if let Some(supports) = &supports {
span.end = supports.span().end;
}
if let Some(media) = &media {
span.end = media.span.end;
}
if let Some(modifiers) = &modifiers
&& modifiers.span.end > modifiers.span.start
{
span.end = modifiers.span.end;
}
Ok(ImportPrelude { href, layer, supports, media, modifiers, span })
}
}
impl<'a> ImportPrelude<'a> {
/// The standard post-URL grammar: optional `layer`/`layer(...)`, optional
/// `supports(...)`, optional media query list — valid only if it accounts
/// for everything up to the end of the statement.
#[allow(clippy::type_complexity)]
fn parse_structured_tail(
input: &mut Parser<'a>,
) -> PResult<(
Option<ImportPreludeLayer<'a>>,
Option<ImportPreludeSupports<'a>>,
Option<MediaQueryList<'a>>,
)> {
let layer =
if input.cursor.peek()?.is_ident_name_eq_ignore_ascii_case(input.source, "layer") {
let ident = input.parse::<Ident>()?;
let layer = match input.cursor.peek()? {
TokenWithSpan { token: Token::LParen(..), span }
if span.start == ident.span.end =>
{
input.cursor.bump()?;
let layer_name = input.parse().map(ComponentValue::LayerName)?;
let args = input.vec1(layer_name);
let end = input.cursor.expect_r_paren()?.1.end;
let span = Span { start: ident.span.start, end };
ImportPreludeLayer::WithName(Function {
name: FunctionName::Ident(InterpolableIdent::Literal(ident)),
args,
span,
})
}
_ => ImportPreludeLayer::Empty(ident),
};
Some(layer)
} else {
None
};
let supports = input.try_parse(|parser| {
// (kept as its own try so a non-`supports` ident rolls back)
let (ident, span) = parser.cursor.expect_ident()?;
if !ident.name().eq_ignore_ascii_case("supports") {
return Err(Error { kind: ErrorKind::TryParseError, span });
}
parser.cursor.expect_l_paren_without_ws_or_comments()?;
let kind = if let Ok(supports_condition) = parser.try_parse(SupportsCondition::parse) {
ImportPreludeSupportsKind::SupportsCondition(supports_condition)
} else {
parser.parse().map(ImportPreludeSupportsKind::Declaration)?
};
let (_, Span { end, .. }) = parser.cursor.expect_r_paren()?;
Ok(ImportPreludeSupports { kind, span: Span { start: span.start, end } })
});
// `}` ends the at-rule too, so an `@import` nested in a style rule needs no
// trailing `;` (`a { @import "b.css" }`); it can't start a media query.
let media = if at_import_prelude_end(&input.cursor.peek()?.token) {
None
} else {
Some(input.parse::<MediaQueryList>()?)
};
// Anything left over means this tail isn't the standard grammar.
if at_import_prelude_end(&input.cursor.peek()?.token) {
Ok((layer, supports.ok(), media))
} else {
let span = input.cursor.peek()?.span;
Err(Error { kind: ErrorKind::TryParseError, span })
}
}
}
/// End of an `@import` prelude: the statement boundary tokens.
fn at_import_prelude_end(token: &Token) -> bool {
matches!(
token,
Token::Semicolon(..)
| Token::Eof(..)
| Token::RBrace(..)
| Token::Dedent(..)
| Token::Linebreak(..)
)
}