Elide the explicit any namespace prefix when lacking default namespace.

Once again it seems we don't need to preserve the original prefix name,
and this lets to_css serialize to the shortest form when there is no
default namespace and the *| prefix is used.

Selectors § 6.1.1 says:

    Element type selectors that have no namespace component (no namespace
    separator) represent elements without regard to the element's namespace
    (equivalent to "*|") unless a default namespace has been declared for
    namespaced selectors (e.g. in CSS, in the style sheet). If a default
    namespace has been declared, such selectors will represent only elements
    in the default namespace.

Then if there is no default namespace, *| (which we write as
QNamePrefix::ExplicitAnyNamespace) is equivalent to what we write as
QNamePrefix::ImplicitAnyNamespace; the latter has a shorter
serialization, so we should use that.

components/selectors/parser.rs

@@ -1026,7 +1026,21 @@ fn parse_type_selector<'i, 't, P, E, Impl, S>(parser: &P, input: &mut CssParser<
                     sink.push(Component::ExplicitNoNamespace)
                 }
                 QNamePrefix::ExplicitAnyNamespace => {
-                    sink.push(Component::ExplicitAnyNamespace)
+                    match parser.default_namespace() {
+                        // Element type selectors that have no namespace
+                        // component (no namespace separator) represent elements
+                        // without regard to the element's namespace (equivalent
+                        // to "*|") unless a default namespace has been declared
+                        // for namespaced selectors (e.g. in CSS, in the style
+                        // sheet). If a default namespace has been declared,
+                        // such selectors will represent only elements in the
+                        // default namespace.
+                        // -- Selectors § 6.1.1
+                        // So we'll have this act the same as the
+                        // QNamePrefix::ImplicitAnyNamespace case.
+                        None => {},
+                        Some(_) => sink.push(Component::ExplicitAnyNamespace),
+                    }
                 }
                 QNamePrefix::ImplicitNoNamespace => {
                     unreachable!()  // Not returned with in_attr_selector = false
@@ -1643,6 +1657,15 @@ pub mod tests {
         ns_prefixes: HashMap<DummyAtom, DummyAtom>,
     }
 
+    impl DummyParser {
+        fn default_with_namespace(default_ns: DummyAtom) -> DummyParser {
+            DummyParser {
+                default_ns: Some(default_ns),
+                ns_prefixes: Default::default(),
+            }
+        }
+    }
+
     impl SelectorImpl for DummySelectorImpl {
         type AttrValue = DummyAtom;
         type Identifier = DummyAtom;
@@ -1732,19 +1755,40 @@ pub mod tests {
         }
     }
 
-    fn parse<'i>(input: &'i str) -> Result<SelectorList<DummySelectorImpl>,
+    fn parse<'i>(input: &'i str)
-                                           ParseError<'i, SelectorParseError<'i, ()>>> {
+                 -> Result<SelectorList<DummySelectorImpl>, ParseError<'i, SelectorParseError<'i, ()>>> {
         parse_ns(input, &DummyParser::default())
     }
 
+    fn parse_expected<'i, 'a>(input: &'i str, expected: Option<&'a str>)
+                              -> Result<SelectorList<DummySelectorImpl>, ParseError<'i, SelectorParseError<'i, ()>>> {
+        parse_ns_expected(input, &DummyParser::default(), expected)
+    }
+
     fn parse_ns<'i>(input: &'i str, parser: &DummyParser)
-                    -> Result<SelectorList<DummySelectorImpl>,
+                    -> Result<SelectorList<DummySelectorImpl>, ParseError<'i, SelectorParseError<'i, ()>>> {
-                              ParseError<'i, SelectorParseError<'i, ()>>> {
+        parse_ns_expected(input, parser, None)
+    }
+
+    fn parse_ns_expected<'i, 'a>(
+        input: &'i str,
+        parser: &DummyParser,
+        expected: Option<&'a str>
+    ) -> Result<SelectorList<DummySelectorImpl>, ParseError<'i, SelectorParseError<'i, ()>>> {
         let mut parser_input = ParserInput::new(input);
         let result = SelectorList::parse(parser, &mut CssParser::new(&mut parser_input));
         if let Ok(ref selectors) = result {
             assert_eq!(selectors.0.len(), 1);
-            assert_eq!(selectors.0[0].to_css_string(), input);
+            // We can't assume that the serialized parsed selector will equal
+            // the input; for example, if there is no default namespace, '*|foo'
+            // should serialize to 'foo'.
+            assert_eq!(
+                selectors.0[0].to_css_string(),
+                match expected {
+                    Some(x) => x,
+                    None => input
+                }
+            );
         }
         result
     }
@@ -1783,16 +1827,34 @@ pub mod tests {
                     lower_name: DummyAtom::from("e")
                 })), specificity(0, 0, 1))
         ))));
-        // https://github.com/servo/servo/issues/16020
+        // When the default namespace is not set, *| should be elided.
-        assert_eq!(parse("*|e"), Ok(SelectorList::from_vec(vec!(
+        // https://github.com/servo/servo/pull/17537
+        assert_eq!(parse_expected("*|e", Some("e")), Ok(SelectorList::from_vec(vec!(
             Selector::from_vec(vec!(
-                Component::ExplicitAnyNamespace,
                 Component::LocalName(LocalName {
                     name: DummyAtom::from("e"),
                     lower_name: DummyAtom::from("e")
                 })
             ), specificity(0, 0, 1))
         ))));
+        // When the default namespace is set, *| should _not_ be elided (as foo
+        // is no longer equivalent to *|foo--the former is only for foo in the
+        // default namespace).
+        // https://github.com/servo/servo/issues/16020
+        assert_eq!(
+            parse_ns(
+                "*|e",
+                &DummyParser::default_with_namespace(DummyAtom::from("https://mozilla.org"))
+            ),
+            Ok(SelectorList::from_vec(vec!(
+                Selector::from_vec(vec!(
+                    Component::ExplicitAnyNamespace,
+                    Component::LocalName(LocalName {
+                        name: DummyAtom::from("e"),
+                        lower_name: DummyAtom::from("e")
+                    })
+                ), specificity(0, 0, 1)))))
+        );
         assert_eq!(parse("*"), Ok(SelectorList::from_vec(vec!(
             Selector::from_vec(vec!(
                 Component::ExplicitUniversalType,
@@ -1804,12 +1866,22 @@ pub mod tests {
                 Component::ExplicitUniversalType,
             ), specificity(0, 0, 0))
         ))));
-        assert_eq!(parse("*|*"), Ok(SelectorList::from_vec(vec!(
+        assert_eq!(parse_expected("*|*", Some("*")), Ok(SelectorList::from_vec(vec!(
             Selector::from_vec(vec!(
-                Component::ExplicitAnyNamespace,
                 Component::ExplicitUniversalType,
             ), specificity(0, 0, 0))
         ))));
+        assert_eq!(
+            parse_ns(
+                "*|*",
+                &DummyParser::default_with_namespace(DummyAtom::from("https://mozilla.org"))
+            ),
+            Ok(SelectorList::from_vec(vec!(
+                Selector::from_vec(vec!(
+                    Component::ExplicitAnyNamespace,
+                    Component::ExplicitUniversalType,
+                ), specificity(0, 0, 0)))))
+        );
         assert_eq!(parse(".foo:lang(en-US)"), Ok(SelectorList::from_vec(vec!(
             Selector::from_vec(vec!(
                     Component::Class(DummyAtom::from("foo")),
@@ -2029,10 +2101,11 @@ pub mod tests {
                 ].into_boxed_slice()
             )), specificity(0, 0, 0))
         ))));
-        assert_eq!(parse_ns(":not(*|*)", &parser), Ok(SelectorList::from_vec(vec!(
+        // *| should be elided if there is no default namespace.
+        // https://github.com/servo/servo/pull/17537
+        assert_eq!(parse_ns_expected(":not(*|*)", &parser, Some(":not(*)")), Ok(SelectorList::from_vec(vec!(
             Selector::from_vec(vec!(Component::Negation(
                 vec![
-                    Component::ExplicitAnyNamespace,
                     Component::ExplicitUniversalType,
                 ].into_boxed_slice()
             )), specificity(0, 0, 0))
@@ -2063,7 +2136,10 @@ pub mod tests {
 
     #[test]
     fn test_universal() {
-        let selector = &parse("*|*::before").unwrap().0[0];
+        let selector = &parse_ns(
+            "*|*::before",
+            &DummyParser::default_with_namespace(DummyAtom::from("https://mozilla.org"))
+        ).unwrap().0[0];
         assert!(selector.is_universal());
     }
 

tests/wpt/metadata-css/cssom-1_dev/html/serialize-namespaced-type-selectors.htm.ini

@@ -1,26 +1,5 @@
 [serialize-namespaced-type-selectors.htm]
   type: testharness
-  [Type selector with any namespace]
-    expected: FAIL
-
-  [Universal selector in any namespace]
-    expected: FAIL
-
-  [Type selector with any namespace followed by class]
-    expected: FAIL
-
-  [Type selector with any namespace followed by id]
-    expected: FAIL
-
-  [Type selector with any namespace followed by pseudo class]
-    expected: FAIL
-
-  [Type selector with any namespace followed by pseudo element]
-    expected: FAIL
-
-  [Type selector with any namespace followed by attribute selector]
-    expected: FAIL
-
   [Universal selector followed by class]
     expected: FAIL
 
@@ -51,27 +30,6 @@
   [Universal selector in any namespace followed by attribute selector]
     expected: FAIL
 
-  [Type selector with namespace equal to default namespace]
-    expected: FAIL
-
-  [Universal selector with namespace equal to default namespace]
-    expected: FAIL
-
-  [Type selector with namespace equal to default namespace followed by class]
-    expected: FAIL
-
-  [Type selector with namespace equal to default namespace followed by id]
-    expected: FAIL
-
-  [Type selector with namespace equal to default namespace followed by pseudo class]
-    expected: FAIL
-
-  [Type selector with namespace equal to default namespace followed by pseudo element]
-    expected: FAIL
-
-  [Type selector with namespace equal to default namespace followed by attribute selector]
-    expected: FAIL
-
   [Universal selector with namespace equal to default namespace followed by class]
     expected: FAIL
 

tests/wpt/metadata/cssom/serialize-namespaced-type-selectors.html.ini

@@ -1,26 +1,5 @@
 [serialize-namespaced-type-selectors.html]
   type: testharness
-  [Type selector with any namespace]
-    expected: FAIL
-
-  [Universal selector in any namespace]
-    expected: FAIL
-
-  [Type selector with any namespace followed by class]
-    expected: FAIL
-
-  [Type selector with any namespace followed by id]
-    expected: FAIL
-
-  [Type selector with any namespace followed by pseudo class]
-    expected: FAIL
-
-  [Type selector with any namespace followed by pseudo element]
-    expected: FAIL
-
-  [Type selector with any namespace followed by attribute selector]
-    expected: FAIL
-
   [Universal selector followed by class]
     expected: FAIL
 
@@ -51,27 +30,6 @@
   [Universal selector in any namespace followed by attribute selector]
     expected: FAIL
 
-  [Type selector with namespace equal to default namespace]
-    expected: FAIL
-
-  [Universal selector with namespace equal to default namespace]
-    expected: FAIL
-
-  [Type selector with namespace equal to default namespace followed by class]
-    expected: FAIL
-
-  [Type selector with namespace equal to default namespace followed by id]
-    expected: FAIL
-
-  [Type selector with namespace equal to default namespace followed by pseudo class]
-    expected: FAIL
-
-  [Type selector with namespace equal to default namespace followed by pseudo element]
-    expected: FAIL
-
-  [Type selector with namespace equal to default namespace followed by attribute selector]
-    expected: FAIL
-
   [Universal selector with namespace equal to default namespace followed by class]
     expected: FAIL