IO-870: PathUtils.copyFileToDirectory (#728)

* IO-870: PathUtils.copyFileToDirectory
span FileSystem.

* Add test

* null check

Author: dsmiley

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

@@ -321,7 +321,18 @@ public static Path copyFile(final URL sourceFile, final Path targetFile, final C
      * @see Files#copy(Path, Path, CopyOption...)
      */
     public static Path copyFileToDirectory(final Path sourceFile, final Path targetDirectory, final CopyOption... copyOptions) throws IOException {
-        return Files.copy(sourceFile, targetDirectory.resolve(sourceFile.getFileName()), copyOptions);
+        // Path.resolve() naturally won't work across FileSystem unless we convert to a String
+        final Path sourceFileName = sourceFile.getFileName();
+        if (sourceFileName == null) {
+            throw new IllegalArgumentException("must have a file name: " + sourceFile);
+        }
+        final Path targetFile;
+        if (sourceFileName.getFileSystem() == targetDirectory.getFileSystem()) {
+            targetFile = targetDirectory.resolve(sourceFileName);
+        } else {
+            targetFile = targetDirectory.resolve(sourceFileName.toString());
+        }
+        return Files.copy(sourceFile, targetFile, copyOptions);
     }
 
     /**

src/test/java/org/apache/commons/io/file/PathUtilsTest.java

@@ -178,6 +178,16 @@ public void testCopyFile() throws IOException {
         assertEquals(Files.size(sourceFile), Files.size(targetFile));
     }
 
+    @Test
+    public void testCopyFileTwoFileSystem() throws IOException {
+        try (FileSystem archive = openArchive(Paths.get(TEST_JAR_PATH), false)) {
+            final Path sourceFile = archive.getPath("next/dir/test.log");
+            final Path targetFile = PathUtils.copyFileToDirectory(sourceFile, tempDirPath);
+            assertTrue(Files.exists(targetFile));
+            assertEquals(Files.size(sourceFile), Files.size(targetFile));
+        }
+    }
+
     @Test
     public void testCopyURL() throws IOException {
         final Path sourceFile = Paths.get("src/test/resources/org/apache/commons/io/dirs-1-file-size-1/file-size-1.bin");