style: Correctly track whether a longhand contains any variable.

components/style/properties/declaration_block.rs

@@ -333,7 +333,9 @@ impl PropertyDeclarationBlock {
                 }
                 let iter = self.declarations.iter().map(get_declaration as fn(_) -> _);
                 match shorthand.get_shorthand_appendable_value(iter) {
-                    Some(AppendableValue::Css(css)) => dest.write_str(css),
+                    Some(AppendableValue::Css { css, .. }) => {
+                        dest.write_str(css)
+                    },
                     Some(AppendableValue::DeclarationsForShorthand(_, decls)) => {
                         shorthand.longhands_to_css(decls, dest)
                     }
@@ -428,15 +430,25 @@ impl ToCss for PropertyDeclarationBlock {
                         Importance::Normal
                     };
 
-                    // Substep 5 - Let value be the result of invoking serialize a CSS
+                    // Substep 5 - Let value be the result of invoking serialize
-                    // value of current longhands.
+                    // a CSS value of current longhands.
                     let mut value = String::new();
+                    let has_variables = {
+                        let appendable_value =
                             match shorthand.get_shorthand_appendable_value(current_longhands.iter().cloned()) {
                                 None => continue,
-                        Some(appendable_value) => {
+                                Some(appendable_value) => appendable_value,
-                            try!(append_declaration_value(&mut value, appendable_value));
+                            };
-                        }
+
-                    }
+                        let has_variables = match appendable_value {
+                            AppendableValue::Css { with_variables, .. } => with_variables,
+                            _ => false,
+                        };
+
+                        append_declaration_value(&mut value, appendable_value)?;
+
+                        has_variables
+                    };
 
                     // Substep 6
                     if value.is_empty() {
@@ -444,9 +456,12 @@ impl ToCss for PropertyDeclarationBlock {
                     }
 
                     // Substeps 7 and 8
-                    try!(append_serialization::<W, Cloned<slice::Iter< _>>, _>(
+                    append_serialization::<_, Cloned<slice::Iter< _>>, _>(
-                             dest, &shorthand, AppendableValue::Css(&value), importance,
+                         dest,
-                             &mut is_first_serialization));
+                         &shorthand,
+                         AppendableValue::Css { css: &value, with_variables: has_variables },
+                         importance,
+                         &mut is_first_serialization)?;
 
                     for current_longhand in current_longhands {
                         // Substep 9
@@ -503,7 +518,12 @@ pub enum AppendableValue<'a, I>
     DeclarationsForShorthand(ShorthandId, I),
     /// A raw CSS string, coming for example from a property with CSS variables,
     /// or when storing a serialized shorthand value before appending directly.
-    Css(&'a str)
+    Css {
+        /// The raw CSS string.
+        css: &'a str,
+        /// Whether the original serialization contained variables or not.
+        with_variables: bool,
+    }
 }
 
 /// Potentially appends whitespace after the first (property: value;) pair.
@@ -513,12 +533,11 @@ fn handle_first_serialization<W>(dest: &mut W,
     where W: fmt::Write,
 {
     if !*is_first_serialization {
-        try!(write!(dest, " "));
+        dest.write_str(" ")
     } else {
         *is_first_serialization = false;
-    }
-
         Ok(())
+    }
 }
 
 /// Append a given kind of appendable value to a serialization.
@@ -529,18 +548,16 @@ pub fn append_declaration_value<'a, W, I>(dest: &mut W,
           I: Iterator<Item=&'a PropertyDeclaration>,
 {
     match appendable_value {
-        AppendableValue::Css(css) => {
+        AppendableValue::Css { css, .. } => {
-            try!(write!(dest, "{}", css))
+            dest.write_str(css)
         },
         AppendableValue::Declaration(decl) => {
-            try!(decl.to_css(dest));
+            decl.to_css(dest)
         },
         AppendableValue::DeclarationsForShorthand(shorthand, decls) => {
-            try!(shorthand.longhands_to_css(decls, dest));
+            shorthand.longhands_to_css(decls, dest)
         }
     }
-
-    Ok(())
 }
 
 /// Append a given property and value pair to a serialization.
@@ -560,17 +577,21 @@ pub fn append_serialization<'a, W, I, N>(dest: &mut W,
     try!(dest.write_char(':'));
 
     // for normal parsed values, add a space between key: and value
-    match &appendable_value {
+    match appendable_value {
-        &AppendableValue::Declaration(decl) => {
+        AppendableValue::Declaration(decl) => {
             if !decl.value_is_unparsed() {
-                // for normal parsed values, add a space between key: and value
+                // For normal parsed values, add a space between key: and value.
-                try!(write!(dest, " "));
+                dest.write_str(" ")?
             }
         },
+        AppendableValue::Css { with_variables, .. } => {
+            if !with_variables {
+                dest.write_str(" ")?
+            }
+        }
         // Currently append_serialization is only called with a Css or
         // a Declaration AppendableValue.
-        &AppendableValue::DeclarationsForShorthand(..) => unreachable!(),
+        AppendableValue::DeclarationsForShorthand(..) => unreachable!(),
-        &AppendableValue::Css(_) => {}
     }
 
     try!(append_declaration_value(dest, appendable_value));

components/style/properties/properties.mako.rs

@@ -580,7 +580,10 @@ impl ShorthandId {
         // https://drafts.csswg.org/css-variables/#variables-in-shorthands
         if let Some(css) = first_declaration.with_variables_from_shorthand(self) {
             if declarations2.all(|d| d.with_variables_from_shorthand(self) == Some(css)) {
-               return Some(AppendableValue::Css(css));
+               return Some(AppendableValue::Css {
+                   css: css,
+                   with_variables: true,
+               });
             }
             return None;
         }
@@ -588,7 +591,10 @@ impl ShorthandId {
         // Check whether they are all the same CSS-wide keyword.
         if let Some(keyword) = first_declaration.get_css_wide_keyword() {
             if declarations2.all(|d| d.get_css_wide_keyword() == Some(keyword)) {
-                return Some(AppendableValue::Css(keyword.to_str()));
+                return Some(AppendableValue::Css {
+                    css: keyword.to_str(),
+                    with_variables: false,
+                });
             }
             return None;
         }