[7.x.x] Improve spec compliance of fn:parse-xml-fragment

exist-core/pom.xml

@@ -781,6 +781,7 @@
                                 <include>src/test/resources/standalone-webapp/WEB-INF/web.xml</include>
                                 <include>src/test/xquery/maps/maps.xqm</include>
                                 <include>src/test/xquery/util/util.xml</include>
+                                <include>src/test/xquery/xquery3/parse-xml.xqm</include>
                                 <include>src/test/xquery/xquery3/serialize.xql</include>
                                 <include>src/main/java/org/exist/Indexer.java</include>
                                 <include>src/main/resources-filtered/org/exist/system.properties</include>
@@ -1007,6 +1008,7 @@
                                 <exclude>src/test/xquery/xqsuite/xqsuite-assertions-inline.xqm</exclude>
                                 <exclude>src/test/xquery/xqsuite/xqsuite-assertions.resources.xqm.ignore</exclude>
                                 <exclude>src/test/xquery/xquery3/function-reference.xqm</exclude>
+                                <exclude>src/test/xquery/xquery3/parse-xml.xqm</exclude>
                                 <exclude>src/test/xquery/xquery3/postfix-expr.xqm</exclude>
                                 <exclude>src/test/xquery/xquery3/serialize.xql</exclude>
                                 <exclude>src/main/java/org/exist/Indexer.java</exclude>

exist-core/src/main/java/org/exist/xquery/functions/fn/ParsingFunctions.java

@@ -64,7 +64,6 @@
 
 import java.io.IOException;
 import java.io.StringReader;
-import java.nio.charset.StandardCharsets;
 
 import static org.exist.util.ByteOrderMark.stripXmlBom;
 
@@ -104,10 +103,6 @@ public Sequence eval(final Sequence[] args, final Sequence contextSequence) thro
 			return Sequence.EMPTY_SEQUENCE;
 		}
 		final String xmlContent = args[0].itemAt(0).getStringValue();
-		if (xmlContent.isEmpty()) {
-			return Sequence.EMPTY_SEQUENCE;
-		}
-
         return parse(xmlContent, args);
 	}
 
@@ -134,7 +129,27 @@ private ValidationReport validate(String xmlContent, final SAXAdapter saxAdapter
         xmlContent = stripXmlBom(xmlContent);
         final String xml;
 	    if (isCalledAs("parse-xml-fragment")) {
-            xml = "<" + FRAGMENT_WRAPPER_NAME + ">" + xmlContent + "</" + FRAGMENT_WRAPPER_NAME + ">";
+            String declStr = xmlContent.toLowerCase();
+            final int startIdx = declStr.indexOf("<?xml ");
+            if (startIdx > -1) {
+
+                // NOTE(AR) for parsing fragments the input must be an external entity, so validate that the declaration is a TextDecl (https://www.w3.org/TR/REC-xml/#NT-TextDecl) and not a full XMLDecl (https://www.w3.org/TR/REC-xml/#NT-XMLDecl) with standalone attribute
+
+                declStr = declStr.substring(startIdx);
+                int endIdx = declStr.indexOf("?>");
+                if (endIdx > -1) {
+                    endIdx += 2;
+                }
+                declStr = declStr.substring(0, endIdx);
+                if (declStr.contains("standalone=")) {
+                    throw new XPathException(this, ErrorCodes.FODC0006, "Input to fn:parse-xml-fragment must be a valid external entity, but 'standalone' attribute was detected in the declaration");
+                }
+
+                xml = xmlContent;
+
+            } else {
+                xml = "<" + FRAGMENT_WRAPPER_NAME + ">" + xmlContent + "</" + FRAGMENT_WRAPPER_NAME + ">";
+            }
         } else {
 	        xml = xmlContent;
         }

exist-core/src/test/xquery/xquery3/parse-xml.xqm

@@ -0,0 +1,147 @@
+(:
+ : Elemental
+ : Copyright (C) 2024, Evolved Binary Ltd
+ :
+ : [email protected]
+ : https://www.evolvedbinary.com | https://www.elemental.xyz
+ :
+ : This library is free software; you can redistribute it and/or
+ : modify it under the terms of the GNU Lesser General Public
+ : License as published by the Free Software Foundation; version 2.1.
+ :
+ : This library is distributed in the hope that it will be useful,
+ : but WITHOUT ANY WARRANTY; without even the implied warranty of
+ : MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ : Lesser General Public License for more details.
+ :
+ : You should have received a copy of the GNU Lesser General Public
+ : License along with this library; if not, write to the Free Software
+ : Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ :
+ : NOTE: Parts of this file contain code from 'The eXist-db Authors'.
+ :       The original license header is included below.
+ :
+ : =====================================================================
+ :
+ : eXist-db Open Source Native XML Database
+ : Copyright (C) 2001 The eXist-db Authors
+ :
+ : [email protected]
+ : http://www.exist-db.org
+ :
+ : This library is free software; you can redistribute it and/or
+ : modify it under the terms of the GNU Lesser General Public
+ : License as published by the Free Software Foundation; either
+ : version 2.1 of the License, or (at your option) any later version.
+ :
+ : This library is distributed in the hope that it will be useful,
+ : but WITHOUT ANY WARRANTY; without even the implied warranty of
+ : MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ : Lesser General Public License for more details.
+ :
+ : You should have received a copy of the GNU Lesser General Public
+ : License along with this library; if not, write to the Free Software
+ : Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ :)
+xquery version "3.0";
+
+(:~ Additional tests for the fn:parse-xml and fn:parse-xml-fragment functions :)
+module namespace px="http://exist-db.org/xquery/test/parse-xml";
+
+declare namespace test="http://exist-db.org/xquery/xqsuite";
+
+declare
+    %test:assertEmpty
+function px:fragment-type-1() {
+    fn:parse-xml-fragment(())
+};
+
+declare
+    %test:assertTrue
+function px:fragment-type-2() {
+    fn:parse-xml-fragment("") instance of document-node()
+};
+
+declare
+    %test:assertEmpty
+function px:fragment-children-1() {
+    fn:parse-xml-fragment("")/node()
+};
+
+declare
+    %test:assertTrue
+function px:fragment-type-3() {
+    fn:parse-xml-fragment(" ") instance of document-node()
+};
+
+declare
+    %test:assertTrue(" ")
+function px:fragment-children-2() {
+    fn:parse-xml-fragment(" ")/node()
+};
+
+declare
+    %test:assertTrue
+function px:fragment-type-4() {
+    fn:parse-xml-fragment("<alpha>abcd</alpha><beta>abcd</beta>") instance of document-node()
+};
+
+declare
+    %test:assertEquals("<alpha>abcd</alpha>", "<beta>abcd</beta>")
+function px:fragment-children-3() {
+    fn:parse-xml-fragment("<alpha>abcd</alpha><beta>abcd</beta>")/node()
+};
+
+declare
+    %test:assertTrue
+function px:fragment-type-5() {
+    fn:parse-xml-fragment("He was <i>so</i> kind") instance of document-node()
+};
+
+declare
+    %test:assertEquals(1)
+function px:fragment-count() {
+    count(parse-xml-fragment("He was <i>so</i> kind"))
+};
+
+declare
+    %test:assertEquals(3)
+function px:fragment-node-count() {
+    count(parse-xml-fragment("He was <i>so</i> kind")/node())
+};
+
+declare
+    %test:assertTrue
+function px:fragment-xml-decl() {
+    fn:parse-xml-fragment('<?xml version="1.0"?><a/>') instance of document-node()
+};
+
+declare
+    %test:assertError("FODC0006")
+function px:fragment-xml-decl-standalone-yes() {
+    fn:parse-xml-fragment('<?xml version="1.0" standalone="yes"?><a/>')
+};
+
+declare
+    %test:assertError("FODC0006")
+function px:fragment-xml-decl-standalone-no() {
+    fn:parse-xml-fragment('<?xml version="1.0" standalone="no"?><a/>')
+};
+
+declare
+    %test:assertTrue
+function px:fragment-xml-decl-encoding() {
+    fn:parse-xml-fragment('<?xml version="1.0" encoding="utf8"?><a/>') instance of document-node()
+};
+
+declare
+    %test:assertError("FODC0006")
+function px:fragment-xml-decl-encoding-standalone-yes() {
+    fn:parse-xml-fragment('<?xml version="1.0" encoding="utf8" standalone="yes"?><a/>')
+};
+
+declare
+    %test:assertError("FODC0006")
+function px:fragment-xml-decl-encoding-standalone-no() {
+    fn:parse-xml-fragment('<?xml version="1.0" encoding="utf8" standalone="no"?><a/>')
+};