From 336ccdb5f1c97cd20000c010abb0b0b523a86731 Mon Sep 17 00:00:00 2001
From: Sam Atkins <sam@ladybird.org>
Date: Fri, 11 Apr 2025 15:37:52 +0100
Subject: [PATCH] LibWeb/XML: Treat declared namespaces as valid for attributes

Previously if we encountered any attributes with a namespace other than
`xml` or `xmlns`, we treated it as a parse error. Now, allow it as long
as it's been declared in the current context.

We also handle errors more gracefully - instead of exploding if setting
the namespace fails, treat it as an error and carry on.
---
 Libraries/LibWeb/XML/XMLDocumentBuilder.cpp   | 28 +++++++++++--------
 .../svg/custom-namespaced-attributes-ref.svg  |  8 ++++++
 .../svg/custom-namespaced-attributes.svg      | 11 ++++++++
 3 files changed, 36 insertions(+), 11 deletions(-)
 create mode 100644 Tests/LibWeb/Ref/expected/svg/custom-namespaced-attributes-ref.svg
 create mode 100644 Tests/LibWeb/Ref/input/svg/custom-namespaced-attributes.svg

diff --git a/Libraries/LibWeb/XML/XMLDocumentBuilder.cpp b/Libraries/LibWeb/XML/XMLDocumentBuilder.cpp
index b6299957ddc..8a0b3e5ae4b 100644
--- a/Libraries/LibWeb/XML/XMLDocumentBuilder.cpp
+++ b/Libraries/LibWeb/XML/XMLDocumentBuilder.cpp
@@ -152,21 +152,27 @@ void XMLDocumentBuilder::element_start(const XML::Name& name, HashMap<XML::Name,
     }
 
     for (auto const& attribute : attributes) {
-        // https://www.w3.org/TR/2006/REC-xml-names11-20060816/#ns-decl
         if (attribute.key == "xmlns" || attribute.key.starts_with("xmlns:"sv)) {
-            auto name = attribute.key;
-            if (!name.is_one_of("xmlns:"sv, "xmlns:xmlns"sv)) {
-                // The prefix xmlns is used only to declare namespace bindings and is by definition bound to the namespace name http://www.w3.org/2000/xmlns/.
-                MUST(node->set_attribute_ns(Namespace::XMLNS, MUST(String::from_byte_string(name)), MUST(String::from_byte_string(attribute.value))));
-            } else {
-                m_has_error = true;
+            // The prefix xmlns is used only to declare namespace bindings and is by definition bound to the namespace name http://www.w3.org/2000/xmlns/.
+            if (!attribute.key.is_one_of("xmlns:"sv, "xmlns:xmlns"sv)) {
+                if (!node->set_attribute_ns(Namespace::XMLNS, MUST(String::from_byte_string(attribute.key)), MUST(String::from_byte_string(attribute.value))).is_error())
+                    continue;
             }
-        } else if (attribute.key.contains(":"sv)) {
-            if (!attribute.key.starts_with("xml:"sv)) {
-                m_has_error = true;
+            m_has_error = true;
+        } else if (attribute.key.contains(':')) {
+            if (auto ns = namespace_for_name(attribute.key); ns.has_value()) {
+                if (!node->set_attribute_ns(ns.value(), MUST(String::from_byte_string(attribute.key)), MUST(String::from_byte_string(attribute.value))).is_error())
+                    continue;
+            } else if (attribute.key.starts_with("xml:"sv)) {
+                if (auto maybe_error = node->set_attribute_ns(Namespace::XML, MUST(String::from_byte_string(attribute.key)), MUST(String::from_byte_string(attribute.value))); !maybe_error.is_error())
+                    continue;
             }
+            m_has_error = true;
+        } else {
+            if (!node->set_attribute(MUST(String::from_byte_string(attribute.key)), MUST(String::from_byte_string(attribute.value))).is_error())
+                continue;
+            m_has_error = true;
         }
-        MUST(node->set_attribute(MUST(String::from_byte_string(attribute.key)), MUST(String::from_byte_string(attribute.value))));
     }
 
     m_current_node = node.ptr();
diff --git a/Tests/LibWeb/Ref/expected/svg/custom-namespaced-attributes-ref.svg b/Tests/LibWeb/Ref/expected/svg/custom-namespaced-attributes-ref.svg
new file mode 100644
index 00000000000..9fdc887af39
--- /dev/null
+++ b/Tests/LibWeb/Ref/expected/svg/custom-namespaced-attributes-ref.svg
@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<svg:svg
+    width="200"
+    height="200"
+    xmlns:svg="http://www.w3.org/2000/svg"
+>
+     <svg:circle cx="100" cy="100" r="50" fill="#ff0000"/>
+</svg:svg>
diff --git a/Tests/LibWeb/Ref/input/svg/custom-namespaced-attributes.svg b/Tests/LibWeb/Ref/input/svg/custom-namespaced-attributes.svg
new file mode 100644
index 00000000000..c01c4d8be23
--- /dev/null
+++ b/Tests/LibWeb/Ref/input/svg/custom-namespaced-attributes.svg
@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<svg:svg
+    width="200"
+    height="200"
+    xmlns:svg="http://www.w3.org/2000/svg"
+    xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
+    inkscape:test="test"
+>
+     <link rel="match" href="../../expected/svg/custom-namespaced-attributes-ref.svg" />
+     <svg:circle cx="100" cy="100" r="50" fill="#ff0000"/>
+</svg:svg>