Serialize number to no more than necessary precision

Author: upsuper

Cargo.toml

@@ -20,6 +20,7 @@ encoding_rs = "0.5"
 
 [dependencies]
 cssparser-macros = {path = "./macros", version = "0.3"}
+dtoa-short = "0.1"
 heapsize = {version = ">= 0.3, < 0.5", optional = true}
 matches = "0.1"
 phf = "0.7"

src/css-parsing-tests/component_value_list.json

@@ -247,6 +247,12 @@
 	["number", "-0.67", -0.67, "number"]
 ],
 
+"12.3e30 -0.0123e30 9999e-13", [
+	["number", "1.23e31", 1.23e31, "number"], " ",
+	["number", "-1.23e28", -1.23e28, "number"], " ",
+	["number", "9.999e-10", 9.999e-10, "number"]
+],
+
 "3. /* Decimal point must have following digits */", [
 	["number", "3", 3, "integer"], ".", " "
 ],
@@ -264,12 +270,12 @@
 	["percentage", "12", 12, "integer"], " ",
 	["percentage", "+34", 34, "integer"], " ",
 	["percentage", "-45", -45, "integer"], " ",
-	["percentage", "0.66999996", 0.67, "number"], " ",
+	["percentage", "0.67", 0.67, "number"], " ",
 	["percentage", "+0.89", 0.89, "number"], " ",
 	["percentage", "-0.01", -0.01, "number"], " ",
 	["percentage", "2.3", 2.3000000000, "number"], " ",
 	["percentage", "+45.0", 45.0, "number"], " ",
-	["percentage", "-0.66999996", -0.67, "number"]
+	["percentage", "-0.67", -0.67, "number"]
 ],
 
 "12e2% +34e+1% -45E-0% .68e+3% +.79e-1% -.01E2% 2.3E+1% +45.0e6% -0.67e0%", [
@@ -281,7 +287,7 @@
 	["percentage", "-1.0", -1, "number"], " ",
 	["percentage", "23.0", 23, "number"], " ",
 	["percentage", "+45000000.0", 45000000, "number"], " ",
-	["percentage", "-0.66999996", -0.67, "number"]
+	["percentage", "-0.67", -0.67, "number"]
 ],
 
 "12\\% /* Percent sign can not be escaped */", [

src/lib.rs

@@ -68,6 +68,7 @@ fn parse_border_spacing(_context: &ParserContext, input: &mut Parser)
 
 #![recursion_limit="200"]  // For color::parse_color_keyword
 
+extern crate dtoa_short;
 #[macro_use] extern crate cssparser_macros;
 #[macro_use] extern crate matches;
 #[macro_use] extern crate procedural_masquerade;

src/serializer.rs

@@ -2,8 +2,11 @@
  * 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/. */
 
+use dtoa_short;
 use std::ascii::AsciiExt;
+use std::borrow::Cow;
 use std::fmt::{self, Write};
+use std::str;
 
 use super::Token;
 
@@ -41,7 +44,6 @@ pub trait ToCss {
     }
 }
 
-
 #[inline]
 fn write_numeric<W>(value: f32, int_value: Option<i32>, has_sign: bool, dest: &mut W)
                     -> fmt::Result where W: fmt::Write {
@@ -50,15 +52,20 @@ fn write_numeric<W>(value: f32, int_value: Option<i32>, has_sign: bool, dest: &m
         dest.write_str("+")?;
     }
 
-    if value == 0.0 && value.is_sign_negative() {
+    let result = if value == 0.0 && value.is_sign_negative() {
         // Negative zero. Work around #20596.
-        dest.write_str("-0")?
+        Cow::Borrowed("-0")
     } else {
-        write!(dest, "{}", value)?
-    }
+        let mut result = String::new();
+        dtoa_short::write(&mut result, value)?;
+        result.into()
+    };
 
+    dest.write_str(&result)?;
     if int_value.is_none() && value.fract() == 0. {
-        dest.write_str(".0")?;
+        if !result.contains(|c| c == '.' || c == 'e') {
+            dest.write_str(".0")?;
+        }
     }
     Ok(())
 }
@@ -267,7 +274,7 @@ impl<'a, W> fmt::Write for CssStringWriter<'a, W> where W: fmt::Write {
 }
 
 
-macro_rules! impl_tocss_for_number {
+macro_rules! impl_tocss_for_int {
     ($T: ty) => {
         impl<'a> ToCss for $T {
             fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
@@ -277,17 +284,27 @@ macro_rules! impl_tocss_for_number {
     }
 }
 
-impl_tocss_for_number!(f32);
-impl_tocss_for_number!(f64);
-impl_tocss_for_number!(i8);
-impl_tocss_for_number!(u8);
-impl_tocss_for_number!(i16);
-impl_tocss_for_number!(u16);
-impl_tocss_for_number!(i32);
-impl_tocss_for_number!(u32);
-impl_tocss_for_number!(i64);
-impl_tocss_for_number!(u64);
+impl_tocss_for_int!(i8);
+impl_tocss_for_int!(u8);
+impl_tocss_for_int!(i16);
+impl_tocss_for_int!(u16);
+impl_tocss_for_int!(i32);
+impl_tocss_for_int!(u32);
+impl_tocss_for_int!(i64);
+impl_tocss_for_int!(u64);
+
+macro_rules! impl_tocss_for_float {
+    ($T: ty) => {
+        impl<'a> ToCss for $T {
+            fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+                dtoa_short::write(dest, *self)
+            }
+        }
+    }
+}
 
+impl_tocss_for_float!(f32);
+impl_tocss_for_float!(f64);
 
 /// A category of token. See the `needs_separator_when_before` method.
 #[derive(Copy, Clone, Eq, PartialEq, Debug)]

src/tests.rs

@@ -31,7 +31,7 @@ fn almost_equals(a: &Json, b: &Json) -> bool {
         (_, &Json::I64(b)) => almost_equals(a, &Json::F64(b as f64)),
         (_, &Json::U64(b)) => almost_equals(a, &Json::F64(b as f64)),
 
-        (&Json::F64(a), &Json::F64(b)) => (a - b).abs() < 1e-6,
+        (&Json::F64(a), &Json::F64(b)) => (a - b).abs() <= a.abs() * 1e-6,
 
         (&Json::Boolean(a), &Json::Boolean(b)) => a == b,
         (&Json::String(ref a), &Json::String(ref b)) => a == b,
@@ -1004,3 +1004,25 @@ fn parse_comments() {
         assert_eq!(parser.current_source_map_url(), test.1);
     }
 }
+
+#[test]
+fn roundtrip_percentage_token() {
+    fn test_roundtrip(value: &str) {
+        let mut input = ParserInput::new(value);
+        let mut parser = Parser::new(&mut input);
+        let token = parser.next().unwrap();
+        assert_eq!(token.to_css_string(), value);
+    }
+    // Test simple number serialization
+    for i in 0..101 {
+        test_roundtrip(&format!("{}%", i));
+        for j in 0..10 {
+            if j != 0 {
+                test_roundtrip(&format!("{}.{}%", i, j));
+            }
+            for k in 1..10 {
+                test_roundtrip(&format!("{}.{}{}%", i, j, k));
+            }
+        }
+    }
+}