Parse z-index property and fix serialization

Fixes #170

src/lib.rs

@@ -18269,4 +18269,13 @@ mod tests {
       r#".foo{background-image:url(0123abcd)}"#,
     );
   }
+
+  #[test]
+  fn test_zindex() {
+    minify_test(".foo { z-index: 2 }", ".foo{z-index:2}");
+    minify_test(".foo { z-index: -2 }", ".foo{z-index:-2}");
+    minify_test(".foo { z-index: 999999 }", ".foo{z-index:999999}");
+    minify_test(".foo { z-index: 9999999 }", ".foo{z-index:9999999}");
+    minify_test(".foo { z-index: -9999999 }", ".foo{z-index:-9999999}");
+  }
 }

src/properties/mod.rs

@@ -1133,6 +1133,9 @@ define_properties! {
   // https://drafts.fxtf.org/filter-effects-1/
   "filter": Filter(FilterList<'i>, VendorPrefix) / WebKit,
   "backdrop-filter": BackdropFilter(FilterList<'i>, VendorPrefix) / WebKit,
+
+  // https://drafts.csswg.org/css2/
+  "z-index": ZIndex(position::ZIndex),
 }
 
 impl<'i, T: smallvec::Array<Item = V>, V: Parse<'i>> Parse<'i> for SmallVec<T> {

src/properties/position.rs

@@ -1,4 +1,4 @@
-//! The CSS position property.
+//! CSS properties related to positioning.
 
 use super::Property;
 use crate::context::PropertyHandlerContext;
@@ -8,6 +8,7 @@ use crate::prefixes::Feature;
 use crate::printer::Printer;
 use crate::targets::Browsers;
 use crate::traits::{Parse, PropertyHandler, ToCss};
+use crate::values::number::CSSInteger;
 use crate::vendor_prefix::VendorPrefix;
 use cssparser::*;
 
@@ -62,6 +63,38 @@ impl ToCss for Position {
   }
 }
 
+/// A value for the [z-index](https://drafts.csswg.org/css2/#z-index) property.
+#[derive(Debug, Clone, PartialEq)]
+pub enum ZIndex {
+  /// The `auto` keyword.
+  Auto,
+  /// An integer value.
+  Integer(CSSInteger),
+}
+
+impl<'i> Parse<'i> for ZIndex {
+  fn parse<'t>(input: &mut Parser<'i, 't>) -> Result<Self, ParseError<'i, ParserError<'i>>> {
+    if let Ok(value) = input.expect_integer() {
+      return Ok(ZIndex::Integer(value));
+    }
+
+    input.expect_ident_matching("auto")?;
+    Ok(ZIndex::Auto)
+  }
+}
+
+impl ToCss for ZIndex {
+  fn to_css<W>(&self, dest: &mut Printer<W>) -> Result<(), PrinterError>
+  where
+    W: std::fmt::Write,
+  {
+    match self {
+      ZIndex::Auto => dest.write_str("auto"),
+      ZIndex::Integer(value) => value.to_css(dest),
+    }
+  }
+}
+
 #[derive(Default)]
 pub(crate) struct PositionHandler {
   targets: Option<Browsers>,

src/values/number.rs

@@ -32,29 +32,18 @@ impl ToCss for CSSNumber {
   where
     W: std::fmt::Write,
   {
-    use cssparser::ToCss;
     let number = *self;
-    let int_value = if number.fract() == 0.0 {
-      Some(number as i32)
-    } else {
-      None
-    };
-    let tok = Token::Number {
-      has_sign: number < 0.0,
-      value: number,
-      int_value,
-    };
     if number != 0.0 && number.abs() < 1.0 {
       let mut s = String::new();
-      tok.to_css(&mut s)?;
+      cssparser::ToCss::to_css(self, &mut s)?;
       if number < 0.0 {
         dest.write_char('-')?;
         dest.write_str(s.trim_start_matches("-0"))
       } else {
         dest.write_str(s.trim_start_matches('0'))
       }
     } else {
-      tok.to_css(dest)?;
+      cssparser::ToCss::to_css(self, dest)?;
       Ok(())
     }
   }
@@ -91,14 +80,7 @@ impl ToCss for CSSInteger {
   where
     W: std::fmt::Write,
   {
-    use cssparser::ToCss;
-    let integer = *self;
-    let tok = Token::Number {
-      has_sign: integer < 0,
-      value: integer as f32,
-      int_value: Some(integer),
-    };
-    tok.to_css(dest)?;
+    cssparser::ToCss::to_css(self, dest)?;
     Ok(())
   }
 }