fix(open): support plain .tar archives in Opener

- include 'tar' in ARCHIVES detection\n- use tarfile mode 'r:' for uncompressed tar files\n- add regression tests for plain tar extraction

Author: jonsch1

cache_manager/_open.py

@@ -20,7 +20,7 @@
 from cache_manager._session import _log
 
 COMPRESSED =  {'gz', 'xz', 'bz2'}
-ARCHIVES = {'zip', 'tar.gz', 'tar.bz2', 'tar.xz'}
+ARCHIVES = {'zip', 'tar', 'tar.gz', 'tar.bz2', 'tar.xz'}
 
 
 class Opener:
@@ -239,7 +239,8 @@ def open_tar(self):
         self._files = {}
         self.sizes = {}
         compr = self.ext.split('.')[-1]
-        self.tarfile = tarfile.open(fileobj=self.fileobj, mode=f'r:{compr}')
+        mode = 'r:' if self.ext == 'tar' or compr == 'tar' else f'r:{compr}'
+        self.tarfile = tarfile.open(fileobj=self.fileobj, mode=mode)
         self._members = self.tarfile.getmembers()
 
         for m in self._members:

tests/test_open.py

@@ -28,6 +28,23 @@ def temp_tar_gz_file(tmpdir):
     return gz_path
 
 
+@pytest.fixture
+def temp_tar_file(tmpdir):
+
+    subfolder = tmpdir.mkdir('subfolder_plain_tar')
+    file1 = subfolder.join('file1.txt')
+    file2 = subfolder.join('file2.txt')
+    file1.write('This is the first file.')
+    file2.write('This is the second file.')
+
+    tar_path = tmpdir.join('archive.tar')
+
+    with tarfile.open(tar_path, 'w:') as tar:
+        tar.add(subfolder.strpath, arcname=os.path.basename(subfolder.strpath))
+
+    return tar_path
+
+
 @pytest.fixture
 def temp_xz_file(tmpdir):
 
@@ -138,3 +155,25 @@ def test_open_tar_gz(temp_tar_gz_file):
     opener = _open.Opener(temp_tar_gz_file.strpath, large = False)
 
     assert opener.result['subfolder/file1.txt'] == b'This is the first file.'
+
+
+def test_open_plain_tar(temp_tar_file):
+
+    opener = _open.Opener(temp_tar_file.strpath, ext='tar')
+
+    assert isinstance(opener.result, dict)
+    assert set(opener.result.keys()) == {
+        'subfolder_plain_tar/file1.txt',
+        'subfolder_plain_tar/file2.txt',
+    }
+    assert (
+        opener.result['subfolder_plain_tar/file1.txt'].read() ==
+        b'This is the first file.'
+    )
+
+    opener = _open.Opener(temp_tar_file.strpath, ext='tar', large=False)
+
+    assert (
+        opener.result['subfolder_plain_tar/file2.txt'] ==
+        b'This is the second file.'
+    )