Handle !default

src/common.rs

@@ -218,6 +218,7 @@ pub enum Keyword {
     True,
     False,
     Null,
+    Default,
     // Infinity,
     // NaN,
     // Auto,
@@ -237,6 +238,7 @@ impl Display for Keyword {
             Self::True => write!(f, "true"),
             Self::False => write!(f, "false"),
             Self::Null => write!(f, "null"),
+            Self::Default => write!(f, "!default"),
             // Self::Infinity => write!(f, "Infinity"),
             // Self::NaN => write!(f, "NaN"),
             // Self::Auto => write!(f, "auto"),
@@ -258,6 +260,7 @@ impl Into<&'static str> for Keyword {
             Self::True => "true",
             Self::False => "false",
             Self::Null => "null",
+            Self::Default => "!default",
             // Self::Infinity => "Infinity",
             // Self::NaN => "NaN",
             // Self::Auto => "auto",
@@ -282,6 +285,7 @@ impl TryFrom<&str> for Keyword {
             "true" => Ok(Self::True),
             "false" => Ok(Self::False),
             "null" => Ok(Self::Null),
+            "default" => Ok(Self::Default),
             // "infinity" => Ok(Self::Infinity),
             // "nan" => Ok(Self::NaN),
             // "auto" => Ok(Self::Auto),

src/lexer.rs

@@ -117,14 +117,19 @@ impl<'a> Lexer<'a> {
             Some('i') | Some('I') => {
                 self.buf.next();
                 assert_char!(self, 'm' 'p' 'o' 'r' 't' 'a' 'n' 't');
+                TokenKind::Keyword(Keyword::Important)
+            }
+            Some('d') | Some('D') => {
+                self.buf.next();
+                assert_char!(self, 'e' 'f' 'a' 'u' 'l' 't');
+                TokenKind::Keyword(Keyword::Default)
             }
             Some('=') => {
                 self.buf.next();
-                return TokenKind::Op(Op::NotEqual);
+                TokenKind::Op(Op::NotEqual)
             }
             _ => todo!("expected either `i` or `=` after `!`"),
-        };
+        }
-        TokenKind::Keyword(Keyword::Important)
     }
 
     fn devour_whitespace(&mut self) -> bool {

src/lib.rs

@@ -58,7 +58,7 @@ use crate::lexer::Lexer;
 use crate::mixin::{eat_include, Mixin};
 use crate::selector::{Attribute, Selector};
 use crate::style::Style;
-use crate::utils::{devour_whitespace, eat_variable_value, IsComment, IsWhitespace};
+use crate::utils::{devour_whitespace, eat_variable_value, IsComment, IsWhitespace, VariableDecl};
 use crate::value::Value;
 
 mod args;
@@ -346,9 +346,11 @@ impl<'a> StyleSheetParser<'a> {
                     {
                         self.error(pos, "unexpected variable use at toplevel");
                     }
-                    let val = eat_variable_value(&mut self.lexer, &self.global_scope)
+                    let VariableDecl { val, default } = eat_variable_value(&mut self.lexer, &self.global_scope)
                         .unwrap_or_else(|err| self.error(err.0, &err.1));
-                    self.global_scope.vars.insert(name, val);
+                    if !default || self.global_scope.vars.get(&name).is_none() {
+                        self.global_scope.vars.insert(name, val);
+                    }
                 }
                 TokenKind::MultilineComment(_) => {
                     let comment = match self
@@ -533,10 +535,10 @@ pub(crate) fn eat_expr<I: Iterator<Item = Token>>(
                 {
                     toks.next();
                     devour_whitespace(toks);
-                    return Ok(Some(Expr::VariableDecl(
+                    let VariableDecl { val, default } = eat_variable_value(toks, scope)?;
-                        name,
+                    if !default || scope.vars.get(&name).is_none() {
-                        eat_variable_value(toks, scope)?,
+                        return Ok(Some(Expr::VariableDecl(name, val)));
-                    )));
+                    }
                 } else {
                     values.push(Token {
                         kind: TokenKind::Variable(name),

src/selector.rs

@@ -272,7 +272,9 @@ impl<'a> SelectorParser<'a> {
                 TokenKind::Symbol(Symbol::Plus) => self.selectors.push(SelectorKind::Following),
                 TokenKind::Symbol(Symbol::Tilde) => self.selectors.push(SelectorKind::Preceding),
                 TokenKind::Symbol(Symbol::Mul) => self.selectors.push(SelectorKind::Universal),
-                TokenKind::Symbol(Symbol::Percent) => self.selectors.push(SelectorKind::Placeholder),
+                TokenKind::Symbol(Symbol::Percent) => {
+                    self.selectors.push(SelectorKind::Placeholder)
+                }
                 TokenKind::Symbol(Symbol::BitAnd) => self.selectors.push(if self.is_interpolated {
                     SelectorKind::InterpolatedSuper
                 } else {

src/utils.rs

@@ -1,4 +1,4 @@
-use crate::common::{Pos, Symbol};
+use crate::common::{Keyword, Pos, Symbol};
 use crate::lexer::Lexer;
 use crate::value::Value;
 use crate::{Scope, Token, TokenKind};
@@ -64,15 +64,51 @@ pub(crate) fn eat_interpolation<I: Iterator<Item = Token>>(
     val
 }
 
+pub(crate) struct VariableDecl {
+    pub val: Value,
+    pub default: bool,
+}
+
+impl VariableDecl {
+    pub fn new(val: Value, default: bool) -> VariableDecl {
+        VariableDecl { val, default }
+    }
+}
+
 pub(crate) fn eat_variable_value<I: Iterator<Item = Token>>(
     toks: &mut Peekable<I>,
     scope: &Scope,
-) -> Result<Value, (Pos, String)> {
+) -> Result<VariableDecl, (Pos, String)> {
     devour_whitespace(toks);
-    // todo!(line might not end with semicolon)
+    let mut default = false;
-    let iter1: Vec<Token> = toks
+    let mut raw: Vec<Token> = Vec::new();
-        .take_while(|x| x.kind != TokenKind::Symbol(Symbol::SemiColon))
+    let mut nesting = 0;
-        .collect();
+    while let Some(tok) = toks.peek() {
+        match tok.kind {
+            TokenKind::Symbol(Symbol::SemiColon) => {
+                toks.next();
+                break;
+            }
+            TokenKind::Keyword(Keyword::Default) => {
+                toks.next();
+                default = true
+            }
+            TokenKind::Interpolation | TokenKind::Symbol(Symbol::OpenCurlyBrace) => {
+                nesting += 1;
+                raw.push(toks.next().unwrap());
+            }
+            TokenKind::Symbol(Symbol::CloseCurlyBrace) => {
+                if nesting == 0 {
+                    break;
+                } else {
+                    nesting -= 1;
+                    raw.push(toks.next().unwrap());
+                }
+            }
+            _ => raw.push(toks.next().unwrap()),
+        }
+    }
     devour_whitespace(toks);
-    Ok(Value::from_tokens(&mut iter1.into_iter().peekable(), scope).unwrap())
+    let val = Value::from_tokens(&mut raw.into_iter().peekable(), scope).unwrap();
+    Ok(VariableDecl::new(val, default))
 }

src/value.rs

@@ -304,7 +304,9 @@ impl Value {
                 }
                 Some(Value::Ident(s, QuoteKind::Single))
             }
-            TokenKind::Variable(ref v) => Some(scope.vars.get(v).expect("expected variable").clone()),
+            TokenKind::Variable(ref v) => {
+                Some(scope.vars.get(v).expect("expected variable").clone())
+            }
             TokenKind::Interpolation => {
                 let mut s = eat_interpolation(toks, scope)
                     .iter()

tests/main.rs

@@ -100,6 +100,36 @@ mod test_variables {
         "$var1: red; a {\n  color: $var1;\n}\n",
         "a {\n  color: red;\n}\n"
     );
+    test!(
+        default_var_after,
+        "$a: red;\n$a: blue !default;\na {\n  color: $a;\n}",
+        "a {\n  color: red;\n}\n"
+    );
+    test!(
+        default_var_before,
+        "$a: red !default;\n$a: blue;\na {\n  color: $a;\n}",
+        "a {\n  color: blue;\n}\n"
+    );
+    test!(
+        default_var_whitespace,
+        "$a: red     !default          ;\na {\n  color: $a;\n}",
+        "a {\n  color: red;\n}\n"
+    );
+    test!(
+        default_var_inside_rule,
+        "a {\n  $a: red;\n  $a: blue !default;\n  color: $a;\n}",
+        "a {\n  color: red;\n}\n"
+    );
+    test!(
+        interpolation_in_variable,
+        "$a: #{red};\na {\n  color: $a\n}\n",
+        "a {\n  color: red;\n}\n"
+    );
+    test!(
+        variable_decl_doesnt_end_in_semicolon,
+        "a {\n  $a: red\n}\n\nb {\n  color: blue;\n}\n",
+        "b {\n  color: blue;\n}\n"
+    );
 }
 
 #[cfg(test)]