Add variable support for Include Controller

==============

- Add variable support for includePath
- Add tests for getIncludePathAsFunction()

src/components/src/main/java/org/apache/jmeter/control/IncludeController.java

@@ -22,6 +22,8 @@
 import java.io.IOException;
 import java.util.ArrayList;
 
+import org.apache.jmeter.engine.util.CompoundVariable;
+import org.apache.jmeter.functions.InvalidVariableException;
 import org.apache.jmeter.gui.tree.JMeterTreeNode;
 import org.apache.jmeter.save.SaveService;
 import org.apache.jmeter.services.FileServer;
@@ -92,6 +94,32 @@ public String getIncludePath() {
         return this.getPropertyAsString(INCLUDE_PATH);
     }
 
+    /**
+     * return the JMX file path with function support.
+     * @return the JMX file path with function support
+     */
+    public String getIncludePathAsFunction()
+    {
+        String jmxfile = this.getPropertyAsString(INCLUDE_PATH);
+        CompoundVariable masterFunction = new CompoundVariable();
+        try{
+            log.debug("Trying to evaluate 'Include Path' as an expression: {}", jmxfile);
+            masterFunction.setParameters(jmxfile);
+            if(masterFunction.hasFunction()) {
+                String jmxfileCompile = masterFunction.getFunction().execute();
+                log.debug("The value of 'Include Path' is computed as: {}", jmxfileCompile);
+                return jmxfileCompile;
+            }
+        } catch (InvalidVariableException e)
+        {
+            log.warn("Invalid variable in 'Include Path' {}. See log for details", jmxfile);
+            log.warn("Invalid variable in 'Include Path':", e);
+        }
+
+        log.debug("The value of 'Include Path' is simple string: {}", jmxfile);
+        return jmxfile;
+    }
+
     /**
      * The way ReplaceableController works is clone is called first,
      * followed by replace(HashTree) and finally getReplacement().
@@ -117,7 +145,7 @@ public void resolveReplacementSubTree(JMeterTreeNode context) {
      */
     protected HashTree loadIncludedElements() {
         // only try to load the JMX test plan if there is one
-        final String includePath = getIncludePath();
+        final String includePath = getIncludePathAsFunction();
         HashTree tree = null;
         if (includePath != null && includePath.length() > 0) {
             String fileName=PREFIX+includePath;

src/components/src/test/java/org/apache/jmeter/control/TestIncludeController.java

@@ -0,0 +1,96 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to you under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.jmeter.control;
+
+import static org.junit.Assert.assertEquals;
+
+import org.apache.jmeter.junit.JMeterTestCase;
+import org.apache.jmeter.threads.JMeterContext;
+import org.apache.jmeter.threads.JMeterContextService;
+import org.apache.jmeter.threads.JMeterVariables;
+import org.junit.jupiter.api.Test;
+
+public class TestIncludeController extends JMeterTestCase {
+
+
+    @Test
+    public void testGetIncludePathWithVariable() {
+        String varName = "testGetIncludePathWithVariable_file_name";
+        String varValue = "C:\\testPath\\testFile.jmx";
+        String varExpression = "${" + varName + "}";
+
+        JMeterVariables vars = new JMeterVariables();
+        JMeterContext jmctx = JMeterContextService.getContext();
+
+        jmctx.setVariables(vars);
+        vars.put(varName, varValue);
+
+        IncludeController includeController = new IncludeController();
+        includeController.setIncludePath(varExpression);
+
+        assertEquals(varValue, includeController.getIncludePathAsFunction());
+    }
+
+    @Test
+    public void testGetIncludePathWithVariables() {
+        String dirName = "var1";
+        String dirValue = "/tmp/path/test";
+
+        String fileName = "var2";
+        String fileValue = "testFile.jmx";
+
+        String varExpression = "${" + dirName + "}/${" + fileName + "}";
+
+        JMeterVariables vars = new JMeterVariables();
+        JMeterContext jmctx = JMeterContextService.getContext();
+
+        jmctx.setVariables(vars);
+        vars.put(dirName, dirValue);
+        vars.put(fileName, fileValue);
+
+        IncludeController includeController = new IncludeController();
+        includeController.setIncludePath(varExpression);
+
+        assertEquals(dirValue + "/" + fileValue, includeController.getIncludePathAsFunction());
+    }
+
+
+    @Test
+    public void testGetIncludePathWithSimpleString() {
+        String varValue = "C:\\testPath\\testFile.jmx";
+
+        JMeterVariables vars = new JMeterVariables();
+        JMeterContext jmctx = JMeterContextService.getContext();
+
+        IncludeController includeController = new IncludeController();
+        includeController.setIncludePath(varValue);
+
+        assertEquals(varValue, includeController.getIncludePathAsFunction());
+    }
+
+    @Test
+    public void testGetIncludePathWithEmptyString() {
+        String varValue = "";
+
+        IncludeController includeController = new IncludeController();
+        includeController.setIncludePath(varValue);
+
+        assertEquals(varValue, includeController.getIncludePathAsFunction());
+    }
+
+}