Revert "Fix GH-11404: DOMDocument::savexml and friends ommit xmlns="" declaration for null namespace, creating incorrect xml representation of the DOM"

This reverts commit 7eb3e9c.

Although the fix follows the spec, it causes issues because a lot of old
code assumes the incorrect behaviour PHP had since a long time.
We cannot do this yet, especially not in a stable release.
We revert this for the time being.
See GH-11428.

Author: nielsdos

NEWS

@@ -38,8 +38,6 @@ PHP                                                                        NEWS
   . Fix "invalid state error" with cloned namespace declarations. (nielsdos)
   . Fixed bug #55294 and #47530 and #47847 (various namespace reconciliation
     issues). (nielsdos)
-  . Fixed bug GH-11404 (DOMDocument::saveXML and friends omit xmlns=""
-    declaration for null namespace). (nielsdos)
   . Fixed bug #80332 (Completely broken array access functionality with
     DOMNamedNodeMap). (nielsdos)
 

ext/dom/document.c

@@ -878,10 +878,6 @@ PHP_METHOD(DOMDocument, createElementNS)
 
 	if (errorcode == 0) {
 		if (xmlValidateName((xmlChar *) localname, 0) == 0) {
-			/* https://dom.spec.whatwg.org/#validate-and-extract: demands us to set an empty string uri to NULL */
-			if (uri_len == 0) {
-				uri = NULL;
-			}
 			nodep = xmlNewDocNode(docp, NULL, (xmlChar *) localname, (xmlChar *) value);
 			if (nodep != NULL && uri != NULL) {
 				nsptr = xmlSearchNsByHref(nodep->doc, nodep, (xmlChar *) uri);

ext/dom/element.c

@@ -56,10 +56,6 @@ PHP_METHOD(DOMElement, __construct)
 	if (uri_len > 0) {
 		errorcode = dom_check_qname(name, &localname, &prefix, uri_len, name_len);
 		if (errorcode == 0) {
-			/* https://dom.spec.whatwg.org/#validate-and-extract: demands us to set an empty string uri to NULL */
-			if (uri_len == 0) {
-				uri = NULL;
-			}
 			nodep = xmlNewNode (NULL, (xmlChar *)localname);
 			if (nodep != NULL && uri != NULL) {
 				nsptr = dom_get_ns(nodep, uri, &errorcode, prefix);

ext/dom/node.c

@@ -531,6 +531,7 @@ Since: DOM Level 2
 int dom_node_namespace_uri_read(dom_object *obj, zval *retval)
 {
 	xmlNode *nodep = dom_object_get_node(obj);
+	char *str = NULL;
 
 	if (nodep == NULL) {
 		php_dom_throw_error(INVALID_STATE_ERR, 1);
@@ -542,19 +543,20 @@ int dom_node_namespace_uri_read(dom_object *obj, zval *retval)
 		case XML_ATTRIBUTE_NODE:
 		case XML_NAMESPACE_DECL:
 			if (nodep->ns != NULL) {
-				char *str = (char *) nodep->ns->href;
-				/* https://dom.spec.whatwg.org/#concept-attribute: namespaceUri is "null or a non-empty string" */
-				if (str != NULL && str[0] != '\0') {
-					ZVAL_STRING(retval, str);
-					return SUCCESS;
-				}
+				str = (char *) nodep->ns->href;
 			}
 			break;
 		default:
+			str = NULL;
 			break;
 	}
 
-	ZVAL_NULL(retval);
+	if (str != NULL) {
+		ZVAL_STRING(retval, str);
+	} else {
+		ZVAL_NULL(retval);
+	}
+
 	return SUCCESS;
 }
 

ext/dom/php_dom.c

@@ -1496,33 +1496,13 @@ static void dom_libxml_reconcile_ensure_namespaces_are_declared(xmlNodePtr nodep
 	xmlDOMWrapReconcileNamespaces(&dummy_ctxt, nodep, /* options */ 0);
 }
 
-static bool dom_must_replace_namespace_by_empty_default(xmlDocPtr doc, xmlNodePtr nodep)
-{
-	xmlNsPtr default_ns = xmlSearchNs(doc, nodep->parent, NULL);
-	return default_ns != NULL && default_ns->href != NULL && default_ns->href[0] != '\0';
-}
-
-static void dom_replace_namespace_by_empty_default(xmlDocPtr doc, xmlNodePtr nodep)
-{
-	ZEND_ASSERT(nodep->ns == NULL);
-	/* The node uses the default empty namespace, but the current default namespace is non-empty.
-	 * We can't unconditionally do this because otherwise libxml2 creates an xmlns="" declaration.
-	 * Note: there's no point searching the oldNs list, because we haven't found it in the tree anyway.
-	 *       Ideally this would be pre-allocated but unfortunately libxml2 doesn't offer such a functionality. */
-	xmlSetNs(nodep, xmlNewNs(nodep, (const xmlChar *) "", NULL));
-}
-
 void dom_reconcile_ns(xmlDocPtr doc, xmlNodePtr nodep) /* {{{ */
 {
 	/* Although the node type will be checked by the libxml2 API,
 	 * we still want to do the internal reconciliation conditionally. */
 	if (nodep->type == XML_ELEMENT_NODE) {
 		dom_reconcile_ns_internal(doc, nodep, nodep->parent);
 		dom_libxml_reconcile_ensure_namespaces_are_declared(nodep);
-		/* Check nodep->ns first to avoid an expensive lookup. */
-		if (nodep->ns == NULL && dom_must_replace_namespace_by_empty_default(doc, nodep)) {
-			dom_replace_namespace_by_empty_default(doc, nodep);
-		}
 	}
 }
 /* }}} */
@@ -1546,30 +1526,12 @@ static void dom_reconcile_ns_list_internal(xmlDocPtr doc, xmlNodePtr nodep, xmlN
 
 void dom_reconcile_ns_list(xmlDocPtr doc, xmlNodePtr nodep, xmlNodePtr last)
 {
-	bool did_compute_must_replace_namespace_by_empty_default = false;
-	bool must_replace_namespace_by_empty_default = false;
-
 	dom_reconcile_ns_list_internal(doc, nodep, last, nodep->parent);
-
 	/* The loop is outside of the recursion in the above call because
 	 * dom_libxml_reconcile_ensure_namespaces_are_declared() performs its own recursion. */
 	while (true) {
 		/* The internal libxml2 call will already check the node type, no need for us to do it here. */
 		dom_libxml_reconcile_ensure_namespaces_are_declared(nodep);
-
-		/* We don't have to handle the children, because if their ns's are NULL they'll just take on the default
-		 * which should've been reconciled before. */
-		if (nodep->ns == NULL) {
-			/* This is an optimistic approach: we assume that most of the time we don't need the result of the computation. */
-			if (!did_compute_must_replace_namespace_by_empty_default) {
-				did_compute_must_replace_namespace_by_empty_default = true;
-				must_replace_namespace_by_empty_default = dom_must_replace_namespace_by_empty_default(doc, nodep);
-			}
-			if (must_replace_namespace_by_empty_default) {
-				dom_replace_namespace_by_empty_default(doc, nodep);
-			}
-		}
-
 		if (nodep == last) {
 			break;
 		}

ext/dom/tests/bug47530.phpt

@@ -121,7 +121,7 @@ test_appendChild_with_shadowing();
 <html xmlns="https://php.net/something" xmlns:ns="https://php.net/whatever"><element ns:foo="https://php.net/bar"/></html>
 -- Test document fragment without import --
 <?xml version="1.0"?>
-<html xmlns=""><element xmlns:foo="https://php.net/bar"><foo:bar/><bar/></element></html>
+<html xmlns=""><element xmlns:foo="https://php.net/bar"><foo:bar/><bar xmlns=""/></element></html>
 string(7) "foo:bar"
 string(19) "https://php.net/bar"
 -- Test document import --