fix incorrect warning in the junit task when includeAntRuntime="no"

fixed by making the classloader used by checkForkedPath behave like a real forked classpath, thus completely isolated from the launching jvm

WHATSNEW

@@ -10,6 +10,9 @@ Fixed bugs:
    is 'true'.
    Bugzilla Report 60062
 
+ * The junit task when used with includeantruntime="no" was incorrectly
+   printing a warning about multiple versions of ant detected in path
+
 Changes from Ant 1.10.2 TO Ant 1.10.3
 =====================================
 

src/etc/testcases/taskdefs/optional/junit.xml

@@ -354,4 +354,19 @@
     </junit>
   </target>
 
+  <target name="testCheckForkedPath">
+    <property name="includeantruntime" value="yes" />
+    <!-- duplicate the Ant classes into a jar -->
+    <jar destfile="${output}/ant.jar" basedir="${antclasses}" />
+    <junit fork="yes" haltonerror="true" haltonfailure="true"
+             showoutput="${showoutput}" includeantruntime="${includeantruntime}">
+      <test name="org.example.junit.Output" />
+      <classpath>
+        <pathelement location="../../../../../build/testcases" />
+        <pathelement location="${junitjar}" />
+        <pathelement location="${output}/ant.jar" />
+      </classpath>
+    </junit>
+  </target>
+
 </project>

src/main/org/apache/tools/ant/taskdefs/optional/junit/JUnitTask.java

@@ -1368,9 +1368,10 @@ public class JUnitTask extends Task {
             return;
         }
         try (AntClassLoader loader =
-             AntClassLoader.newAntClassLoader(null, getProject(),
-                                              cmd.createClasspath(getProject()),
-                                              true)) {
+            AntClassLoader.newAntClassLoader(null, getProject(),
+                                             cmd.createClasspath(getProject()),
+                                             false)) {
+            loader.setIsolated(true);
             final String projectResourceName =
                 LoaderUtils.classNameToResource(Project.class.getName());
             URL previous = null;

src/tests/junit/org/apache/tools/ant/taskdefs/optional/junit/JUnitTaskTest.java

@@ -577,6 +577,36 @@ public class JUnitTaskTest {
         }
     }
 
+    private void setupCheckDuplicateTest() {
+        final String projectResourceName =
+                LoaderUtils.classNameToResource(Project.class.getName());
+        final File antclasses = LoaderUtils.getResourceSource(
+                Project.class.getClassLoader(), projectResourceName);
+        final String testResourceName =
+                LoaderUtils.classNameToResource(junit.framework.Test.class.getName());
+        final File junitJar = LoaderUtils.getResourceSource(
+                Project.class.getClassLoader(), testResourceName);
+        buildRule.getProject().setProperty("antclasses", antclasses.getAbsolutePath());
+        buildRule.getProject().setProperty("junitjar", junitJar.getAbsolutePath());
+    }
+
+    @Test
+    public void testCheckDuplicateAntJar() throws Exception {
+        setupCheckDuplicateTest();
+        buildRule.executeTarget("testCheckForkedPath");
+        assertTrue("Expecting the warning about the duplicate ant jar",
+                buildRule.getLog().contains("WARNING: multiple versions of ant detected in path for junit"));
+    }
+
+    @Test
+    public void testCheckNonDuplicateAntJar() throws Exception {
+        setupCheckDuplicateTest();
+        buildRule.getProject().setProperty("includeantruntime", "no");
+        buildRule.executeTarget("testCheckForkedPath");
+        assertFalse("Unexpected warning about the duplicate ant jar",
+                buildRule.getLog().contains("WARNING: multiple versions of ant detected in path for junit"));
+    }
+
     private void delete(File f) {
         if (f.isDirectory()) {
             final File[] clds = f.listFiles();