From b743d68ccdab72682e3a87ab0254344d8c6498ee Mon Sep 17 00:00:00 2001
From: Xidorn Quan <me@upsuper.org>
Date: Fri, 20 Oct 2017 14:08:33 +1100
Subject: [PATCH] Accept argument-less tree pseudo-element selector.

---
 .../generated/pseudo_element_definition.rs    | 39 ++++++++++++-------
 .../gecko/pseudo_element_definition.mako.rs   | 20 +++++++---
 components/style/gecko/selector_parser.rs     |  7 ++++
 3 files changed, 46 insertions(+), 20 deletions(-)

diff --git a/components/style/gecko/generated/pseudo_element_definition.rs b/components/style/gecko/generated/pseudo_element_definition.rs
index 83bc1f575c6..2c3e51d703e 100644
--- a/components/style/gecko/generated/pseudo_element_definition.rs
+++ b/components/style/gecko/generated/pseudo_element_definition.rs
@@ -871,6 +871,26 @@ None
         (self.atom().as_ptr(), self.pseudo_type())
     }
 
+    /// Get the argument list of a tree pseudo-element.
+    #[inline]
+    pub fn tree_pseudo_args(&self) -> Option<&[Atom]> {
+        match *self {
+            PseudoElement::MozTreeColumn(ref args) => Some(args),
+            PseudoElement::MozTreeRow(ref args) => Some(args),
+            PseudoElement::MozTreeSeparator(ref args) => Some(args),
+            PseudoElement::MozTreeCell(ref args) => Some(args),
+            PseudoElement::MozTreeIndentation(ref args) => Some(args),
+            PseudoElement::MozTreeLine(ref args) => Some(args),
+            PseudoElement::MozTreeTwisty(ref args) => Some(args),
+            PseudoElement::MozTreeImage(ref args) => Some(args),
+            PseudoElement::MozTreeCellText(ref args) => Some(args),
+            PseudoElement::MozTreeCheckbox(ref args) => Some(args),
+            PseudoElement::MozTreeProgressmeter(ref args) => Some(args),
+            PseudoElement::MozTreeDropFeedback(ref args) => Some(args),
+            _ => None,
+        }
+    }
+
     /// Construct a pseudo-element from an `Atom`.
     #[inline]
     pub fn from_atom(atom: &Atom) -> Option<Self> {
@@ -1768,19 +1788,8 @@ impl ToCss for PseudoElement {
                 PseudoElement::MozSVGForeignContent => dest.write_str(":-moz-svg-foreign-content")?,
                 PseudoElement::MozSVGText => dest.write_str(":-moz-svg-text")?,
         }
-        match *self {
-            PseudoElement::MozTreeColumn(ref args) |
-            PseudoElement::MozTreeRow(ref args) |
-            PseudoElement::MozTreeSeparator(ref args) |
-            PseudoElement::MozTreeCell(ref args) |
-            PseudoElement::MozTreeIndentation(ref args) |
-            PseudoElement::MozTreeLine(ref args) |
-            PseudoElement::MozTreeTwisty(ref args) |
-            PseudoElement::MozTreeImage(ref args) |
-            PseudoElement::MozTreeCellText(ref args) |
-            PseudoElement::MozTreeCheckbox(ref args) |
-            PseudoElement::MozTreeProgressmeter(ref args) |
-            PseudoElement::MozTreeDropFeedback(ref args) => {
+        if let Some(args) = self.tree_pseudo_args() {
+            if !args.is_empty() {
                 dest.write_char('(')?;
                 let mut iter = args.iter();
                 if let Some(first) = iter.next() {
@@ -1790,9 +1799,9 @@ impl ToCss for PseudoElement {
                         serialize_identifier(&item.to_string(), dest)?;
                     }
                 }
-                dest.write_char(')')
+                dest.write_char(')')?;
             }
-            _ => Ok(()),
         }
+        Ok(())
     }
 }
diff --git a/components/style/gecko/pseudo_element_definition.mako.rs b/components/style/gecko/pseudo_element_definition.mako.rs
index b7e5a7614aa..3c7f9e592a7 100644
--- a/components/style/gecko/pseudo_element_definition.mako.rs
+++ b/components/style/gecko/pseudo_element_definition.mako.rs
@@ -147,6 +147,17 @@ impl PseudoElement {
         (self.atom().as_ptr(), self.pseudo_type())
     }
 
+    /// Get the argument list of a tree pseudo-element.
+    #[inline]
+    pub fn tree_pseudo_args(&self) -> Option<<&[Atom]> {
+        match *self {
+            % for pseudo in TREE_PSEUDOS:
+            PseudoElement::${pseudo.capitalized()}(ref args) => Some(args),
+            % endfor
+            _ => None,
+        }
+    }
+
     /// Construct a pseudo-element from an `Atom`.
     #[inline]
     pub fn from_atom(atom: &Atom) -> Option<Self> {
@@ -228,9 +239,8 @@ impl ToCss for PseudoElement {
                 ${pseudo_element_variant(pseudo)} => dest.write_str("${pseudo.value}")?,
             % endfor
         }
-        match *self {
-            ${" |\n            ".join("PseudoElement::{}(ref args)".format(pseudo.capitalized())
-                                      for pseudo in TREE_PSEUDOS)} => {
+        if let Some(args) = self.tree_pseudo_args() {
+            if !args.is_empty() {
                 dest.write_char('(')?;
                 let mut iter = args.iter();
                 if let Some(first) = iter.next() {
@@ -240,9 +250,9 @@ impl ToCss for PseudoElement {
                         serialize_identifier(&item.to_string(), dest)?;
                     }
                 }
-                dest.write_char(')')
+                dest.write_char(')')?;
             }
-            _ => Ok(()),
         }
+        Ok(())
     }
 }
diff --git a/components/style/gecko/selector_parser.rs b/components/style/gecko/selector_parser.rs
index b6d48414fd5..9e4c08f0197 100644
--- a/components/style/gecko/selector_parser.rs
+++ b/components/style/gecko/selector_parser.rs
@@ -379,6 +379,13 @@ impl<'a, 'i> ::selectors::Parser<'i> for SelectorParser<'a> {
     fn parse_pseudo_element(&self, location: SourceLocation, name: CowRcStr<'i>)
                             -> Result<PseudoElement, ParseError<'i>> {
         PseudoElement::from_slice(&name, self.in_user_agent_stylesheet())
+            .or_else(|| {
+                if name.starts_with("-moz-tree-") {
+                    PseudoElement::tree_pseudo_element(&name, Box::new([]))
+                } else {
+                    None
+                }
+            })
             .ok_or(location.new_custom_error(SelectorParseErrorKind::UnsupportedPseudoClassOrElement(name.clone())))
     }