Fix FileFilterTestCase use case for symbolic links on non-Windows OS.

- Make SymbolicLinkFileFilter configurable:
-- Add SymbolicLinkFileFilter.SymbolicLinkFileFilter(FileVisitResult,
FileVisitResult)
-- Add AbstractFileFilter(FileVisitResult, FileVisitResult)
- CountingPathVisitor should not follow links by default to properly
count from FileUtils.

Author: garydgregory

src/main/java/org/apache/commons/io/file/CountingPathVisitor.java

@@ -26,6 +26,7 @@
 import java.util.Objects;
 
 import org.apache.commons.io.file.Counters.PathCounters;
+import org.apache.commons.io.filefilter.SymbolicLinkFileFilter;
 import org.apache.commons.io.filefilter.TrueFileFilter;
 
 /**
@@ -65,7 +66,7 @@ public static CountingPathVisitor withLongCounters() {
      * @param pathCounter How to count path visits.
      */
     public CountingPathVisitor(final PathCounters pathCounter) {
-        this(pathCounter, TrueFileFilter.INSTANCE, TrueFileFilter.INSTANCE);
+        this(pathCounter, new SymbolicLinkFileFilter(FileVisitResult.TERMINATE, FileVisitResult.CONTINUE), TrueFileFilter.INSTANCE);
     }
 
     /**
@@ -149,6 +150,7 @@ protected void updateFileCounters(final Path file, final BasicFileAttributes att
 
     @Override
     public FileVisitResult visitFile(final Path file, final BasicFileAttributes attributes) throws IOException {
+        // Note: A file can be a symbolic link to a directory.
         if (Files.exists(file) && fileFilter.accept(file, attributes) == FileVisitResult.CONTINUE) {
             updateFileCounters(file, attributes);
         }

src/main/java/org/apache/commons/io/file/PathUtils.java

@@ -315,6 +315,7 @@ public static PathCounters countDirectory(final Path directory) throws IOExcepti
      * @param directory directory to delete.
      * @return The visitor used to count the given directory.
      * @throws IOException if an I/O error is thrown by a visitor method.
+     * @since 2.12.0
      */
     public static PathCounters countDirectoryAsBigInteger(final Path directory) throws IOException {
         return visitFileTree(CountingPathVisitor.withBigIntegerCounters(), directory).getPathCounters();

src/main/java/org/apache/commons/io/filefilter/AbstractFileFilter.java

@@ -39,10 +39,39 @@
  */
 public abstract class AbstractFileFilter implements IOFileFilter, PathVisitor {
 
-    static FileVisitResult toFileVisitResult(final boolean accept, final Path path) {
+    static FileVisitResult toDefaultFileVisitResult(final boolean accept) {
         return accept ? FileVisitResult.CONTINUE : FileVisitResult.TERMINATE;
     }
 
+    /**
+     * What to do when this filter accepts.
+     */
+    private final FileVisitResult onAccept;
+
+    /**
+     * What to do when this filter rejects.
+     */
+    private final FileVisitResult onReject;
+
+    /**
+     * Constructs a new instance.
+     */
+    public AbstractFileFilter() {
+        this(FileVisitResult.CONTINUE, FileVisitResult.TERMINATE);
+    }
+
+    /**
+     * Constructs a new instance.
+     *
+     * @param onAccept What to do on acceptance.
+     * @param onReject What to do on rejection.
+     * @since 2.12.0.
+     */
+    protected AbstractFileFilter(final FileVisitResult onAccept, final FileVisitResult onReject) {
+        this.onAccept = onAccept;
+        this.onReject = onReject;
+    }
+
     /**
      * Checks to see if the File should be accepted by this filter.
      *
@@ -89,6 +118,16 @@ public FileVisitResult preVisitDirectory(final Path dir, final BasicFileAttribut
         return accept(dir, attributes);
     }
 
+    /**
+     * Converts a boolean into a FileVisitResult.
+     *
+     * @param accept accepted or rejected.
+     * @return a FileVisitResult.
+     */
+    FileVisitResult toFileVisitResult(final boolean accept) {
+        return accept ? onAccept : onReject;
+    }
+
     /**
      * Provides a String representation of this file filter.
      *

src/main/java/org/apache/commons/io/filefilter/AgeFileFilter.java

@@ -207,7 +207,7 @@ public FileVisitResult accept(final Path file, final BasicFileAttributes attribu
         } catch (final IOException e) {
             return handle(e);
         }
-        return toFileVisitResult(acceptOlder != newer, file);
+        return toFileVisitResult(acceptOlder != newer);
     }
 
     /**

src/main/java/org/apache/commons/io/filefilter/CanExecuteFileFilter.java

@@ -90,7 +90,7 @@ public boolean accept(final File file) {
      */
     @Override
     public FileVisitResult accept(final Path file, final BasicFileAttributes attributes) {
-        return toFileVisitResult(Files.isExecutable(file), file);
+        return toFileVisitResult(Files.isExecutable(file));
     }
 
 }

src/main/java/org/apache/commons/io/filefilter/CanReadFileFilter.java

@@ -100,7 +100,7 @@ public boolean accept(final File file) {
      */
     @Override
     public FileVisitResult accept(final Path file, final BasicFileAttributes attributes) {
-        return toFileVisitResult(Files.isReadable(file), file);
+        return toFileVisitResult(Files.isReadable(file));
     }
 
 }

src/main/java/org/apache/commons/io/filefilter/CanWriteFileFilter.java

@@ -89,7 +89,7 @@ public boolean accept(final File file) {
      */
     @Override
     public FileVisitResult accept(final Path file, final BasicFileAttributes attributes) {
-        return toFileVisitResult(Files.isWritable(file), file);
+        return toFileVisitResult(Files.isWritable(file));
     }
 
 }

src/main/java/org/apache/commons/io/filefilter/DirectoryFileFilter.java

@@ -105,7 +105,7 @@ public boolean accept(final File file) {
      */
     @Override
     public FileVisitResult accept(final Path file, final BasicFileAttributes attributes) {
-        return toFileVisitResult(Files.isDirectory(file), file);
+        return toFileVisitResult(Files.isDirectory(file));
     }
 
 }

src/main/java/org/apache/commons/io/filefilter/EmptyFileFilter.java

@@ -120,10 +120,10 @@ public FileVisitResult accept(final Path file, final BasicFileAttributes attribu
         try {
             if (Files.isDirectory(file)) {
                 try (Stream<Path> stream = Files.list(file)) {
-                    return toFileVisitResult(!stream.findFirst().isPresent(), file);
+                    return toFileVisitResult(!stream.findFirst().isPresent());
                 }
             }
-            return toFileVisitResult(Files.size(file) == 0, file);
+            return toFileVisitResult(Files.size(file) == 0);
         } catch (final IOException e) {
             return handle(e);
         }

src/main/java/org/apache/commons/io/filefilter/FileEqualsFileFilter.java

@@ -52,6 +52,6 @@ public boolean accept(final File file) {
 
     @Override
     public FileVisitResult accept(final Path path, final BasicFileAttributes attributes) {
-        return toFileVisitResult(Objects.equals(this.path, path), path);
+        return toFileVisitResult(Objects.equals(this.path, path));
     }
 }