script: Fix two issues in the XPath parser to pass all xml_xpath_tests.xml tests (#37279)

1. Better handling of namespaces for element and attribute names in XML
mode (read: non-HTML mode)
2. While parsing, pass along context on whether we are in an absolute
(`/`) or descendant (`//`) part of the query, and use it to correctly
enumerate descendants according to where we are in the evaluation of the
AST.

Testing: All 1024 tests in `xml_xpath_tests.xml` (actually
`xml_xpath_runner.html`) pass, as well as some random tests in
`text-html-attributes.html`.
Fixes: #37278

---------

Signed-off-by: Ville Lindholm <ville@lindholm.dev>

components/script/xpath/context.rs

@@ -5,10 +5,14 @@
 use std::iter::Enumerate;
 use std::vec::IntoIter;
 
+use script_bindings::str::DOMString;
+
 use super::Node;
+use crate::dom::bindings::codegen::Bindings::NodeBinding::NodeMethods;
 use crate::dom::bindings::root::DomRoot;
 
 /// The context during evaluation of an XPath expression.
+#[derive(Debug)]
 pub(crate) struct EvaluationCtx {
     /// Where we started at
     pub(crate) starting_node: DomRoot<Node>,
@@ -20,7 +24,7 @@ pub(crate) struct EvaluationCtx {
     pub(crate) predicate_nodes: Option<Vec<DomRoot<Node>>>,
 }
 
-#[derive(Clone, Copy)]
+#[derive(Clone, Copy, Debug)]
 pub(crate) struct PredicateCtx {
     pub(crate) index: usize,
     pub(crate) size: usize,
@@ -68,6 +72,12 @@ impl EvaluationCtx {
             size,
         }
     }
+
+    /// Resolve a namespace prefix using the context node's document
+    pub(crate) fn resolve_namespace(&self, prefix: Option<&str>) -> Option<DOMString> {
+        self.context_node
+            .LookupNamespaceURI(prefix.map(DOMString::from))
+    }
 }
 
 /// When evaluating predicates, we need to keep track of the current node being evaluated and

components/script/xpath/eval.rs

@@ -12,6 +12,7 @@ use super::parser::{
     QName as ParserQualName, RelationalOp, StepExpr, UnaryOp,
 };
 use super::{EvaluationCtx, Value};
+use crate::dom::attr::Attr;
 use crate::dom::bindings::codegen::Bindings::NodeBinding::NodeMethods;
 use crate::dom::bindings::inheritance::{Castable, CharacterDataTypeId, NodeTypeId};
 use crate::dom::bindings::root::DomRoot;
@@ -246,21 +247,31 @@ impl Evaluatable for PathExpr {
     }
 }
 
-impl TryFrom<&ParserQualName> for QualName {
+pub(crate) struct QualNameConverter<'a> {
+    qname: &'a ParserQualName,
+    context: &'a EvaluationCtx,
+}
+
+impl<'a> TryFrom<QualNameConverter<'a>> for QualName {
     type Error = Error;
 
-    fn try_from(qname: &ParserQualName) -> Result<Self, Self::Error> {
-        let qname_as_str = qname.to_string();
-        if let Ok((ns, prefix, local)) = validate_and_extract(None, &qname_as_str) {
+    fn try_from(converter: QualNameConverter<'a>) -> Result<Self, Self::Error> {
+        let qname_as_str = converter.qname.to_string();
+        let namespace = converter
+            .context
+            .resolve_namespace(converter.qname.prefix.as_deref());
+
+        if let Ok((ns, prefix, local)) = validate_and_extract(namespace, &qname_as_str) {
             Ok(QualName { prefix, ns, local })
         } else {
             Err(Error::InvalidQName {
-                qname: qname.clone(),
+                qname: converter.qname.clone(),
             })
         }
     }
 }
 
+#[derive(Debug)]
 pub(crate) enum NameTestComparisonMode {
     /// Namespaces must match exactly
     XHtml,
@@ -310,29 +321,41 @@ pub(crate) fn element_name_test(
     }
 }
 
-fn apply_node_test(test: &NodeTest, node: &Node) -> Result<bool, Error> {
+fn apply_node_test(context: &EvaluationCtx, test: &NodeTest, node: &Node) -> Result<bool, Error> {
     let result = match test {
         NodeTest::Name(qname) => {
             // Convert the unvalidated "parser QualName" into the proper QualName structure
-            let wanted_name: QualName = qname.try_into()?;
-            if matches!(node.type_id(), NodeTypeId::Element(_)) {
-                let element = node.downcast::<Element>().unwrap();
-                let comparison_mode = if node.owner_doc().is_xhtml_document() {
-                    NameTestComparisonMode::XHtml
-                } else {
-                    NameTestComparisonMode::Html
-                };
-                let element_qualname = QualName::new(
-                    element.prefix().as_ref().cloned(),
-                    element.namespace().clone(),
-                    element.local_name().clone(),
-                );
-                element_name_test(wanted_name, element_qualname, comparison_mode)
-            } else {
-                false
+            let wanted_name: QualName = QualNameConverter { qname, context }.try_into()?;
+            match node.type_id() {
+                NodeTypeId::Element(_) => {
+                    let element = node.downcast::<Element>().unwrap();
+                    let comparison_mode = if node.owner_doc().is_html_document() {
+                        NameTestComparisonMode::Html
+                    } else {
+                        NameTestComparisonMode::XHtml
+                    };
+                    let element_qualname = QualName::new(
+                        element.prefix().as_ref().cloned(),
+                        element.namespace().clone(),
+                        element.local_name().clone(),
+                    );
+                    element_name_test(wanted_name, element_qualname, comparison_mode)
+                },
+                NodeTypeId::Attr => {
+                    let attr = node.downcast::<Attr>().unwrap();
+                    let attr_qualname = QualName::new(
+                        attr.prefix().cloned(),
+                        attr.namespace().clone(),
+                        attr.local_name().clone(),
+                    );
+                    // attributes are always compared with strict namespace matching
+                    let comparison_mode = NameTestComparisonMode::XHtml;
+                    element_name_test(wanted_name, attr_qualname, comparison_mode)
+                },
+                _ => false,
             }
         },
-        NodeTest::Wildcard => true,
+        NodeTest::Wildcard => matches!(node.type_id(), NodeTypeId::Element(_)),
         NodeTest::Kind(kind) => match kind {
             KindTest::PI(target) => {
                 if NodeTypeId::CharacterData(CharacterDataTypeId::ProcessingInstruction) ==
@@ -427,7 +450,7 @@ impl Evaluatable for StepExpr {
                 let filtered_nodes: Vec<DomRoot<Node>> = nodes
                     .into_iter()
                     .map(|node| {
-                        apply_node_test(&axis_step.node_test, &node)
+                        apply_node_test(context, &axis_step.node_test, &node)
                             .map(|matches| matches.then_some(node))
                     })
                     .collect::<Result<Vec<_>, _>>()?
@@ -505,6 +528,7 @@ impl Evaluatable for PredicateExpr {
 
                     let v = match eval_result {
                         Ok(Value::Number(v)) => Ok(predicate_ctx.index == v as usize),
+                        Ok(Value::Boolean(v)) => Ok(v),
                         Ok(v) => Ok(v.boolean()),
                         Err(e) => Err(e),
                     };

components/script/xpath/parser.rs

@@ -510,40 +510,45 @@ fn union_expr(input: &str) -> IResult<&str, Expr> {
 fn path_expr(input: &str) -> IResult<&str, Expr> {
     alt((
         // "//" RelativePathExpr
-        map(pair(tag("//"), relative_path_expr), |(_, rel_path)| {
-            Expr::Path(PathExpr {
-                is_absolute: true,
-                is_descendant: true,
-                steps: match rel_path {
-                    Expr::Path(p) => p.steps,
-                    _ => unreachable!(),
-                },
-            })
-        }),
-        // "/" RelativePathExpr?
-        map(pair(char('/'), opt(relative_path_expr)), |(_, rel_path)| {
-            Expr::Path(PathExpr {
-                is_absolute: true,
-                is_descendant: false,
-                steps: rel_path
-                    .map(|p| match p {
+        map(
+            pair(tag("//"), move |i| relative_path_expr(true, i)),
+            |(_, rel_path)| {
+                Expr::Path(PathExpr {
+                    is_absolute: true,
+                    is_descendant: true,
+                    steps: match rel_path {
                         Expr::Path(p) => p.steps,
                         _ => unreachable!(),
-                    })
-                    .unwrap_or_default(),
-            })
-        }),
+                    },
+                })
+            },
+        ),
+        // "/" RelativePathExpr?
+        map(
+            pair(char('/'), opt(move |i| relative_path_expr(false, i))),
+            |(_, rel_path)| {
+                Expr::Path(PathExpr {
+                    is_absolute: true,
+                    is_descendant: false,
+                    steps: rel_path
+                        .map(|p| match p {
+                            Expr::Path(p) => p.steps,
+                            _ => unreachable!(),
+                        })
+                        .unwrap_or_default(),
+                })
+            },
+        ),
         // RelativePathExpr
-        relative_path_expr,
+        move |i| relative_path_expr(false, i),
     ))(input)
 }
 
-fn relative_path_expr(input: &str) -> IResult<&str, Expr> {
-    let (input, first) = step_expr(input)?;
+fn relative_path_expr(is_descendant: bool, input: &str) -> IResult<&str, Expr> {
+    let (input, first) = step_expr(is_descendant, input)?;
     let (input, steps) = many0(pair(
-        // ("/" | "//")
         ws(alt((value(true, tag("//")), value(false, char('/'))))),
-        step_expr,
+        move |i| step_expr(is_descendant, i),
     ))(input)?;
 
     let mut all_steps = vec![first];
@@ -569,16 +574,18 @@ fn relative_path_expr(input: &str) -> IResult<&str, Expr> {
     ))
 }
 
-fn step_expr(input: &str) -> IResult<&str, StepExpr> {
+fn step_expr(is_descendant: bool, input: &str) -> IResult<&str, StepExpr> {
     alt((
         map(filter_expr, StepExpr::Filter),
-        map(axis_step, StepExpr::Axis),
+        map(|i| axis_step(is_descendant, i), StepExpr::Axis),
     ))(input)
 }
 
-fn axis_step(input: &str) -> IResult<&str, AxisStep> {
-    let (input, (step, predicates)) =
-        pair(alt((forward_step, reverse_step)), predicate_list)(input)?;
+fn axis_step(is_descendant: bool, input: &str) -> IResult<&str, AxisStep> {
+    let (input, (step, predicates)) = pair(
+        alt((move |i| forward_step(is_descendant, i), reverse_step)),
+        predicate_list,
+    )(input)?;
 
     let (axis, node_test) = step;
     Ok((
@@ -591,8 +598,10 @@ fn axis_step(input: &str) -> IResult<&str, AxisStep> {
     ))
 }
 
-fn forward_step(input: &str) -> IResult<&str, (Axis, NodeTest)> {
-    alt((pair(forward_axis, node_test), abbrev_forward_step))(input)
+fn forward_step(is_descendant: bool, input: &str) -> IResult<&str, (Axis, NodeTest)> {
+    alt((pair(forward_axis, node_test), move |i| {
+        abbrev_forward_step(is_descendant, i)
+    }))(input)
 }
 
 fn forward_axis(input: &str) -> IResult<&str, Axis> {
@@ -610,7 +619,7 @@ fn forward_axis(input: &str) -> IResult<&str, Axis> {
     Ok((input, axis))
 }
 
-fn abbrev_forward_step(input: &str) -> IResult<&str, (Axis, NodeTest)> {
+fn abbrev_forward_step(is_descendant: bool, input: &str) -> IResult<&str, (Axis, NodeTest)> {
     let (input, attr) = opt(char('@'))(input)?;
     let (input, test) = node_test(input)?;
 
@@ -619,6 +628,8 @@ fn abbrev_forward_step(input: &str) -> IResult<&str, (Axis, NodeTest)> {
         (
             if attr.is_some() {
                 Axis::Attribute
+            } else if is_descendant {
+                Axis::DescendantOrSelf
             } else {
                 Axis::Child
             },

tests/wpt/meta/domxpath/text-html-attributes.html.ini

@@ -1,13 +1,7 @@
 [text-html-attributes.html]
-  [Select html element based on attribute]
-    expected: FAIL
-
   [Select html element based on attribute mixed case]
     expected: FAIL
 
-  [Select both HTML and SVG elements based on attribute]
-    expected: FAIL
-
   [Select HTML element with non-ascii attribute 1]
     expected: FAIL
 
@@ -23,9 +17,6 @@
   [Select both HTML and SVG elements based on mixed case attribute]
     expected: FAIL
 
-  [Select SVG elements with refX attribute]
-    expected: FAIL
-
   [Select SVG element with non-ascii attribute 1]
     expected: FAIL