Fix data_utils.py when name ends with .tar.gz

1. was giving an `UnboundLocal` error.
2. If `fpath` and `untar_fpath` are set to the same value the `untar` doesn't run.
So ensure that `fname` always has `.tar.gz`, and `untar_fpath` never does.

The old behavior (before the previous change) was to always add `.tar.gz`, giving `.tar.gz.tar.gz` files. That seems wrong too.

Fixes tensorflow_docs/site/en/tutorials/load_data/text.ipynb

PiperOrigin-RevId: 380934634

keras/utils/data_utils.py

@@ -24,6 +24,7 @@
 import hashlib
 import multiprocessing.dummy
 import os
+import pathlib
 import queue
 import random
 import shutil
@@ -227,9 +228,14 @@ def get_file(fname=None,
       raise ValueError("Invalid origin '{}'".format(origin))
 
   if untar:
+    if fname.endswith('.tar.gz'):
+      fname = pathlib.Path(fname)
+      # The 2 `.with_suffix()` are because of `.tar.gz` as pathlib
+      # considers it as 2 suffixes.
+      fname = fname.with_suffix('').with_suffix('')
+      fname = str(fname)
     untar_fpath = os.path.join(datadir, fname)
-    if not untar_fpath.endswith('.tar.gz'):
-      fpath = untar_fpath + '.tar.gz'
+    fpath = untar_fpath + '.tar.gz'
   else:
     fpath = os.path.join(datadir, fname)
 

keras/utils/data_utils_test.py

@@ -28,7 +28,7 @@
 from keras.utils import data_utils
 
 
-class TestGetFileAndValidateIt(tf.test.TestCase):
+class TestGetFile(tf.test.TestCase):
 
   def test_get_file_and_validate_it(self):
     """Tests get_file from a url, plus extraction and validation.
@@ -104,6 +104,28 @@ def test_get_file_and_validate_it(self):
     with self.assertRaisesRegexp(ValueError, 'Please specify the "origin".*'):
       _ = keras.utils.data_utils.get_file()
 
+  def test_get_file_with_tgz_extension(self):
+    """Tests get_file from a url, plus extraction and validation."""
+    dest_dir = self.get_temp_dir()
+    orig_dir = self.get_temp_dir()
+
+    text_file_path = os.path.join(orig_dir, 'test.txt')
+    tar_file_path = os.path.join(orig_dir, 'test.tar.gz')
+
+    with open(text_file_path, 'w') as text_file:
+      text_file.write('Float like a butterfly, sting like a bee.')
+
+    with tarfile.open(tar_file_path, 'w:gz') as tar_file:
+      tar_file.add(text_file_path)
+
+    origin = urllib.parse.urljoin(
+        'file://', urllib.request.pathname2url(os.path.abspath(tar_file_path)))
+
+    path = keras.utils.data_utils.get_file(
+        'test.txt.tar.gz', origin, untar=True, cache_subdir=dest_dir)
+    self.assertEndsWith(path, '.txt')
+    self.assertTrue(os.path.exists(path))
+
 
 class TestSequence(keras.utils.data_utils.Sequence):