[IO-499] FilenameUtils.directoryContains false positive issue

src/main/java/org/apache/commons/io/FilenameUtils.java

@@ -529,24 +529,48 @@ public static String concat(final String basePath, final String fullFilenameToAd
      * @since 2.2
      * @see FileUtils#directoryContains(File, File)
      */
-    public static boolean directoryContains(final String canonicalParent, final String canonicalChild)
-            throws IOException {
+     public static boolean directoryContains(final String canonicalParent, final String canonicalChild)
+         throws IOException {
 
-        // Fail fast against NullPointerException
-        if (canonicalParent == null) {
-            throw new IllegalArgumentException("Directory must not be null");
-        }
+     // Fail fast against NullPointerException
+     if (canonicalParent == null) {
+         throw new IllegalArgumentException("Directory must not be null");
+     }
 
-        if (canonicalChild == null) {
-            return false;
-        }
+     if (canonicalChild == null) {
+         return false;
+     }
 
-        if (IOCase.SYSTEM.checkEquals(canonicalParent, canonicalChild)) {
-            return false;
-        }
+     if (IOCase.SYSTEM.checkEquals(canonicalParent, canonicalChild)) {
+         return false;
+     }
 
-        return IOCase.SYSTEM.checkStartsWith(canonicalChild, canonicalParent);
-    }
+     return FilenameUtils.checkStartsWithDir(canonicalParent, canonicalChild);
+
+ }
+
+ /**
+  * Checks if the parent directory contains the child directory/file
+  *
+  * @param parent  the file path to consider as parent
+  * @param child the file path to consider as child
+  * @return true if the parent file path contains the child file path
+  */
+ public static boolean checkStartsWithDir(final String parent, final String child){
+     final int length = parent.length();
+
+     if(length > child.length()){
+         return false;
+     }
+
+     final int splitIndex = child.indexOf('/', length);
+
+     if(splitIndex == -1){
+         return false;
+     }
+
+     return parent.equals(child.substring(0,splitIndex));
+ }
 
     //-----------------------------------------------------------------------
     /**
@@ -715,7 +739,7 @@ public static int indexOfLastSeparator(final String filename) {
      * <p>
      * The output will be the same irrespective of the machine that the code is running on.
      * </p>
-     * 
+     *
      * @param filename
      *            the filename to find the last extension separator in, null returns -1
      * @return the index of the last extension separator character, or -1 if there is no such character

src/test/java/org/apache/commons/io/FileUtilsDirectoryContainsTestCase.java

@@ -5,9 +5,9 @@
  * 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.
@@ -30,7 +30,7 @@
 
 /**
  * This class ensure the correctness of {@link FileUtils#directoryContains(File,File)}.
- * 
+ *
  * @see FileUtils#directoryContains(File, File)
  * @since 2.2
  * @version $Id$
@@ -40,10 +40,10 @@ public class FileUtilsDirectoryContainsTestCase extends FileBasedTestCase {
     private File directory1;
     private File directory2;
     private File directory3;
-    private File file1; 
-    private File file1ByRelativeDirectory2; 
-    private File file2; 
-    private File file2ByRelativeDirectory1; 
+    private File file1;
+    private File file1ByRelativeDirectory2;
+    private File file2;
+    private File file2ByRelativeDirectory1;
     private File file3;
     final File top = getTestDirectory();
 
@@ -178,4 +178,24 @@ public void testUnrealizedContainment() throws IOException {
             // expected
         }
     }
+
+    @Test
+    public void testSimilarStartingCanonicalPath() throws Exception{
+        final File top2 = getTestDirectory();
+        top2.mkdirs();
+
+        File foo = new File(top2, "foo");
+        File foo2 = new File(top2, "foo2");
+
+        foo.mkdir();
+        foo2.mkdir();
+
+        File a = new File(foo, "a.txt");
+        File b = new File(foo2, "b.txt");
+
+        FileUtils.touch(a);
+        FileUtils.touch(b);
+
+        assertFalse(FileUtils.directoryContains(foo, b));
+    }
 }