Bug 1527540 [wpt PR 15343] - domparsing: Fix an issue that XMLSerializer generates new prefix for an attribute with an existing namespace, a=testonly

Automatic update from web-platform-tests
domparsing: Fix an issue that XMLSerializer generates new prefix for an attribute with an existing namespace

Add an implementation of "retrieving a preferred prefix string"
[1], and apply it to attribute serialization.

As the specification defines, this CL introduces another map [2] like:

  namespace URI => [older prefix, ..., newer prefix]

in order to retrieve most-recently-declared prefix.

When we search the map for a prefix, we check availability of
the prefix by the existing prefix-namespace map.

There are two failing test cases in XMLSerializer-serializeToString.html.
They follow the specification.
  * The first failing one: An non-well-formed XML is produced if we follow
    the specification. Chrome's new behavior matches to Firefox. Safari also
    produces a bad XML.
  * The second failing one: Firefox, Safari, and Chrome without this CL
    preserve prefix in such case.  This CL keeps the interoperable behavior.

[1] https://w3c.github.io/DOM-Parsing/#dfn-retrieving-a-preferred-prefix-string
[2] https://w3c.github.io/DOM-Parsing/#dfn-namespace-prefix-map

Bug: 906807
Change-Id: Idaea590ba19c9c21acbaf456ea91ce550c74db5a
Reviewed-on: https://chromium-review.googlesource.com/c/1445033
Commit-Queue: Kent Tamura <tkent@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Auto-Submit: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#631573}

--

wpt-commits: 2647e1e8f6995d12f44edbf0b4fce752e5cb7ec5
wpt-pr: 15343

testing/web-platform/tests/domparsing/XMLSerializer-serializeToString.html

@@ -15,6 +15,15 @@ function createXmlDoc(){
   return parser.parseFromString(input, 'text/xml');
 }
 
+// Returns the root element.
+function parse(xmlString) {
+  return (new DOMParser()).parseFromString(xmlString, 'text/xml').documentElement;
+}
+
+function serialize(node) {
+  return (new XMLSerializer()).serializeToString(node);
+}
+
 test(function() {
   var serializer = new XMLSerializer();
   var root = createXmlDoc().documentElement;
@@ -40,6 +49,58 @@ test(function() {
   assert_equals(xmlString, '<root xmlns="urn:bar"><outer xmlns=""><inner>value1</inner></outer></root>');
 }, 'Check if there is no redundant empty namespace declaration.');
 
+test(function() {
+  let root = parse('<r xmlns:xx="uri"></r>');
+  root.setAttributeNS('uri', 'name', 'v');
+  assert_equals(serialize(root), '<r xmlns:xx="uri" xx:name="v"/>');
+
+  let root2 = parse('<r xmlns:xx="uri"><b/></r>');
+  let child = root2.firstChild;
+  child.setAttributeNS('uri', 'name', 'v');
+  assert_equals(serialize(root2), '<r xmlns:xx="uri"><b xx:name="v"/></r>');
+
+  let root3 = parse('<r xmlns:x0="uri" xmlns:x2="uri"><b xmlns:x1="uri"/></r>');
+  let child3 = root3.firstChild;
+  child3.setAttributeNS('uri', 'name', 'v');
+  assert_equals(serialize(root3),
+                '<r xmlns:x0="uri" xmlns:x2="uri"><b xmlns:x1="uri" x1:name="v"/></r>',
+                'Should choose the nearest prefix');
+}, 'Check if an attribute with namespace and no prefix is serialized with the nearest-declared prefix');
+
+test(function() {
+  let root = parse('<el1 xmlns:p="u1" xmlns:q="u1"><el2 xmlns:q="u2"/></el1>');
+  root.firstChild.setAttributeNS('u1', 'name', 'v');
+  assert_equals(serialize(root),
+                '<el1 xmlns:p="u1" xmlns:q="u1"><el2 xmlns:q="u2" q:name="v"/></el1>');
+  // Maybe this is a specification error.
+}, '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.');
+
+test(function() {
+  let root = parse('<r xmlns:xx="uri"></r>');
+  root.setAttributeNS('uri', 'p:name', 'v');
+  assert_equals(serialize(root), '<r xmlns:xx="uri" xx:name="v"/>');
+
+  let root2 = parse('<r xmlns:xx="uri"><b/></r>');
+  let child = root2.firstChild;
+  child.setAttributeNS('uri', 'p:name', 'value');
+  assert_equals(serialize(root2),
+                '<r xmlns:xx="uri"><b xx:name="value"/></r>');
+}, 'Check if the prefix of an attribute is replaced with another existing prefix mapped to the same namespace URI.');
+
+test(function() {
+  let root = parse('<r xmlns:xx="uri"></r>');
+  root.setAttributeNS('uri2', 'p:name', 'value');
+  assert_equals(serialize(root),
+                '<r xmlns:xx="uri" xmlns:ns1="uri2" ns1:name="value"/>');
+}, 'Check if the prefix of an attribute is NOT preserved in a case where neither its prefix nor its namespace URI is not already used.');
+
+test(function() {
+  let root = parse('<r xmlns:xx="uri"></r>');
+  root.setAttributeNS('uri2', 'xx:name', 'value');
+  assert_equals(serialize(root),
+                '<r xmlns:xx="uri" xmlns:ns1="uri2" ns1:name="value"/>');
+}, 'Check if the prefix of an attribute is replaced with a generated one in a case where the prefix is already mapped to a different namespace URI.');
+
 test(function() {
   var serializer = new XMLSerializer();
   var parser = new DOMParser();