Merge "XMLSerializer: Keep redundant but harmless default namespace d…

…eclarations" to M74 branch

Since crrev.com/632142, XMLSerializer has dropped redundant xmlns="..."
declarations. It matches to IE, Edge, and DOM P&S standard.  This CL
reverts the behavior to unbreak existing applications.  The restored
behavior matches to Firefox and Safari.

* MarkupAccumulator::AppendElement():
  Even if ignore_namespace_definition_attribute_ is set, we drop a
  xmlns="..." only if its value is inconsistent with element's
  namespace.

* MarkupAccumulator::AppendStartTagOpen():
  if local_default_namespace is "" and ns is null, do not emit xmlns="".
  This avoids to serialize xmlns="" twice.

Bug: w3c/DOM-Parsing#47
Bug: 940204
Change-Id: I2978ddc9a3f9511d227a9a1b902f1811ac1c3c07
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1516124
Reviewed-by: Yoshifumi Inoue <[email protected]>
Commit-Queue: Kent Tamura <[email protected]>
Auto-Submit: Kent Tamura <[email protected]>
Cr-Original-Commit-Position: refs/heads/master@{#639873}(cherry picked from commit 31f0236 [formerly 6208aa43211c09758870c44f7dd7c737e2cc3110])
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1524508
Reviewed-by: Kent Tamura <[email protected]>
Cr-Commit-Position: refs/branch-heads/3729@{#147}
Cr-Branched-From: 1926073 [formerly d4a8972e30b604f090aeda5dfff68386ae656267]-refs/heads/master@{#638880}
Former-commit-id: f75d3ff1174b12dce871d1f942ed8798296971c9

third_party/blink/renderer/core/editing/serializers/markup_accumulator.cc

@@ -203,8 +203,12 @@ AtomicString MarkupAccumulator::AppendElement(const Element& element) {
     for (const auto& attribute : element.Attributes()) {
       if (data.ignore_namespace_definition_attribute_ &&
           attribute.NamespaceURI() == xmlns_names::kNamespaceURI &&
-          attribute.Prefix().IsEmpty())
-        continue;
+          attribute.Prefix().IsEmpty()) {
+        // Drop xmlns= only if it's inconsistent with element's namespace.
+        // https://github.com/w3c/DOM-Parsing/issues/47
+        if (!EqualIgnoringNullity(attribute.Value(), element.namespaceURI()))
+          continue;
+      }
       if (!ShouldIgnoreAttribute(element, attribute))
         AppendAttribute(element, attribute);
     }
@@ -315,7 +319,8 @@ MarkupAccumulator::AppendStartTagOpen(const Element& element) {
 
   // 12.6. Otherwise, if local default namespace is null, or local default
   // namespace is not null and its value is not equal to ns, then:
-  if (local_default_namespace.IsNull() || local_default_namespace != ns) {
+  if (local_default_namespace.IsNull() ||
+      !EqualIgnoringNullity(local_default_namespace, ns)) {
     // 12.6.1. Set the ignore namespace definition attribute flag to true.
     data.ignore_namespace_definition_attribute_ = true;
     // 12.6.3. Let the value of inherited ns be ns.
@@ -331,7 +336,7 @@ MarkupAccumulator::AppendStartTagOpen(const Element& element) {
   // 12.7. Otherwise, the node has a local default namespace that matches
   // ns. Append to qualified name the value of node's localName, let the value
   // of inherited ns be ns, and append the value of qualified name to markup.
-  DCHECK_EQ(local_default_namespace, ns);
+  DCHECK(EqualIgnoringNullity(local_default_namespace, ns));
   namespace_context.SetContextNamespace(ns);
   formatter_.AppendStartTagOpen(markup_, element);
   return data;

third_party/blink/web_tests/external/wpt/domparsing/XMLSerializer-serializeToString-expected.txt

@@ -2,6 +2,7 @@ This is a testharness.js-based test.
 PASS check XMLSerializer.serializeToString method could parsing xmldoc to string
 PASS Check if the default namespace is correctly reset.
 PASS Check if there is no redundant empty namespace declaration.
+FAIL Check if redundant xmlns="..." is dropped. assert_equals: expected "<root><child/></root>" but got "<root><child xmlns=\"\"/></root>"
 PASS Check if inconsistent xmlns="..." is dropped.
 PASS Check if an attribute with namespace and no prefix is serialized with the nearest-declared prefix
 FAIL Check if an attribute with namespace and no prefix is serialized with the nearest-declared prefix even if the prefix is assigned to another namespace. assert_equals: expected "<el1 xmlns:p=\"u1\" xmlns:q=\"u1\"><el2 xmlns:q=\"u2\" q:name=\"v\"/></el1>" but got "<el1 xmlns:p=\"u1\" xmlns:q=\"u1\"><el2 xmlns:q=\"u2\" p:name=\"v\"/></el1>"

third_party/blink/web_tests/external/wpt/domparsing/XMLSerializer-serializeToString.html

@@ -45,6 +45,15 @@ <h1>domparsing_XMLSerializer_serializeToString</h1>
   assert_equals(serialize(root), '<root xmlns="urn:bar"><outer xmlns=""><inner>value1</inner></outer></root>');
 }, 'Check if there is no redundant empty namespace declaration.');
 
+test(function() {
+  assert_equals(serialize(parse('<root><child xmlns=""/></root>')),
+                '<root><child/></root>');
+  assert_equals(serialize(parse('<root xmlns=""><child xmlns=""/></root>')),
+                '<root><child/></root>');
+  assert_equals(serialize(parse('<root xmlns="u1"><child xmlns="u1"/></root>')),
+                '<root xmlns="u1"><child/></root>');
+}, 'Check if redundant xmlns="..." is dropped.');
+
 test(function() {
   const root = parse('<root xmlns="uri1"/>');
   const child = root.ownerDocument.createElement('child');
@@ -145,8 +154,6 @@ <h1>domparsing_XMLSerializer_serializeToString</h1>
 
 test(function() {
   assert_equals(serialize(parse('<root><child/></root>')), '<root><child/></root>');
-  assert_equals(serialize(parse('<root><child xmlns=""/></root>')), '<root><child/></root>');
-  assert_equals(serialize(parse('<root xmlns="u1"><child xmlns="u1"/></root>')), '<root xmlns="u1"><child/></root>');
   assert_equals(serialize(parse('<root xmlns="u1"><p:child xmlns:p="u1"/></root>')), '<root xmlns="u1"><child xmlns:p="u1"/></root>');
 }, 'Check if start tag serialization drops element prefix if the namespace is same as inherited default namespace.');