bz-62849 Check for filesystem loops due to symbolic links, in DirectoryScanner and Delete task

src/etc/testcases/core/directoryscanner.xml

@@ -38,4 +38,9 @@
         <touch file="${output}/alpha/beta/gamma/gamma.xml"/>
     </target>
 
+    <target name="symlink-nested-setup" depends="setUp">
+        <symlink link="${output}/alpha/beta/gamma/beta-link" resource="${output}/alpha/beta"/>
+        <touch file="${output}/alpha/beta/gamma/gamma.xml"/>
+    </target>
+
 </project>

src/main/org/apache/tools/ant/DirectoryScanner.java

@@ -1258,6 +1258,18 @@ public class DirectoryScanner
             final String name = vpath + newFile;
             final TokenizedPath newPath = new TokenizedPath(path, newFile);
             final File file = new File(dir, newFile);
+
+            try {
+                // check if it's a filesystem "loop" due to symbolic links
+                if (FileUtils.getFileUtils().isLeadingPath(file.getAbsoluteFile(),
+                    dir.getAbsoluteFile(), true)) {
+                    continue;
+                }
+            } catch (IOException e) {
+                System.err.println("Failed to determine if " + file + " causes a " +
+                        "filesystem loop due to symbolic link; continuing");
+            }
+
             final String[] children = file.list();
             if (children == null || (children.length == 0 && file.isFile())) {
                 if (isIncluded(newPath)) {

src/main/org/apache/tools/ant/taskdefs/Delete.java

@@ -19,6 +19,7 @@
 package org.apache.tools.ant.taskdefs;
 
 import java.io.File;
+import java.io.IOException;
 import java.util.Arrays;
 import java.util.Comparator;
 import java.util.Iterator;
@@ -771,7 +772,19 @@ public class Delete extends MatchingTask {
         }
         for (String s : list) {
             File f = new File(d, s);
-            if (f.isDirectory()) {
+
+            boolean isFsLoop = false;
+
+            try {
+                isFsLoop = SYMLINK_UTILS.isSymbolicLink(f) &&
+                    FileUtils.getFileUtils().isLeadingPath(f.getAbsoluteFile(),
+                        d.getAbsoluteFile(), true);
+            } catch (IOException e) {
+                log("Failed to check if " + f + " causes a filesystem loop due to " +
+                        "symbolic link; continuing");
+            }
+
+            if (f.isDirectory() && !isFsLoop) {
                 removeDir(f);
             } else {
                 log("Deleting " + f.getAbsolutePath(), quiet ? Project.MSG_VERBOSE : verbosity);

src/tests/junit/org/apache/tools/ant/DirectoryScannerTest.java

@@ -132,6 +132,20 @@ public class DirectoryScannerTest {
                 new String[] {"alpha/beta/gamma"});
     }
 
+    @Test
+    public void testAllowRecursiveSymlinks() {
+
+        assumeTrue("Current system does not support Symlinks", supportsSymlinks);
+
+        buildRule.getProject().executeTarget("symlink-nested-setup");
+        DirectoryScanner ds = new DirectoryScanner();
+        ds.setBasedir(new File(buildRule.getProject().getProperty("output")));
+        ds.setIncludes(new String[] {"alpha/beta/gamma/"});
+        ds.scan();
+        compareFiles(ds, new String[] {"alpha/beta/gamma/gamma.xml"},
+            new String[] {"alpha/beta/gamma"});
+    }
+
     @Test
     public void testProhibitSymlinks() {
         assumeTrue("Current system does not support Symlinks", supportsSymlinks);