[feature] Empty stuff for fn:path returns null

Author: alanpaxton

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

@@ -169,6 +169,8 @@ public class FnModule extends AbstractInternalModule {
         new FunctionDef(FunNumber.signatures[1], FunNumber.class),
         new FunctionDef(FunOneOrMore.signature, FunOneOrMore.class),
         new FunctionDef(FnOuterMost.FNS_OUTERMOST, FnOuterMost.class),
+        new FunctionDef(FunPath.FS_PATH_SIGNATURES[0], FunPath.class),
+        new FunctionDef(FunPath.FS_PATH_SIGNATURES[1], FunPath.class),
         new FunctionDef(FunPosition.signature, FunPosition.class),
         new FunctionDef(FunQName.signature, FunQName.class),
         new FunctionDef(FunRemove.signature, FunRemove.class),

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

@@ -0,0 +1,32 @@
+package org.exist.xquery.functions.fn;
+
+import org.exist.dom.QName;
+import org.exist.xquery.*;
+import org.exist.xquery.value.*;
+
+import static org.exist.xquery.FunctionDSL.functionSignature;
+
+public class FunPath extends BasicFunction {
+
+    private static final QName FN_PATH_NAME = new QName("path", Function.BUILTIN_FUNCTION_NS);
+    private static final String FN_PATH_DESCRIPTION =
+            "Returns a path expression that can be used to select the supplied node " +
+                    "relative to the root of its containing document.";
+    private static final FunctionReturnSequenceType FN_PATH_RETURN = new FunctionReturnSequenceType(
+            Type.STRING, Cardinality.ZERO_OR_ONE, "The path expression, or any empty sequence");
+
+    public static final FunctionSignature[] FS_PATH_SIGNATURES = {
+            functionSignature(FunPath.FN_PATH_NAME, FunPath.FN_PATH_DESCRIPTION, FunPath.FN_PATH_RETURN),
+            functionSignature(FunPath.FN_PATH_NAME, FunPath.FN_PATH_DESCRIPTION, FunPath.FN_PATH_RETURN,
+                    new FunctionParameterSequenceType("node", Type.NODE, Cardinality.ZERO_OR_ONE, "The node for which to calculate a path expression"))
+    };
+
+    public FunPath(final XQueryContext context, final FunctionSignature signature) {
+        super(context, signature);
+    }
+
+    @Override
+    public Sequence eval(final Sequence[] args, final Sequence contextSequence) throws XPathException {
+        return Sequence.EMPTY_SEQUENCE;
+    }
+}

exist-core/src/test/xquery/xquery3/fnPath.xql

@@ -0,0 +1,32 @@
+(:
+ : 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 "3.1";
+
+module namespace fnp="http://exist-db.org/xquery/test/function_sort";
+
+declare namespace test="http://exist-db.org/xquery/xqsuite";
+
+declare
+    %test:assertEmpty
+function fnp:empty() {
+    fn:path()
+};