Merge "Add common code for fileutils."

2 files changed, 81 insertions, 0 deletions

diff --git a/openstack/common/fileutils.py b/openstack/common/fileutils.py
index bb2ef61..0c967da 100644
--- a/openstack/common/fileutils.py
+++ b/openstack/common/fileutils.py
@@ -16,9 +16,11 @@
 #    under the License.
 
 
+import contextlib
 import errno
 import os
 
+from openstack.common import excutils
 from openstack.common.gettextutils import _
 from openstack.common import log as logging
 
@@ -65,3 +67,32 @@ def read_cached_file(filename, force_reload=False):
         cache_info['mtime'] = mtime
         reloaded = True
     return (reloaded, cache_info['data'])
+
+
+def delete_if_exists(path):
+    """Delete a file, but ignore file not found error.
+
+    :param path: File to delete
+    """
+
+    try:
+        os.unlink(path)
+    except OSError as e:
+        if e.errno == errno.ENOENT:
+            return
+        else:
+            raise
+
+
+@contextlib.contextmanager
+def remove_path_on_error(path):
+    """Protect code that wants to operate on PATH atomically.
+    Any exception will cause PATH to be removed.
+
+    :param path: File to work with
+    """
+    try:
+        yield
+    except Exception:
+        with excutils.save_and_reraise_exception():
+            delete_if_exists(path)
diff --git a/tests/unit/test_fileutils.py b/tests/unit/test_fileutils.py
index 7cd067c..030f5f0 100644
--- a/tests/unit/test_fileutils.py
+++ b/tests/unit/test_fileutils.py
@@ -16,10 +16,12 @@
 #    under the License.
 
 import __builtin__
+import errno
 import os
 import shutil
 import tempfile
 
+import mock
 import mox
 
 from openstack.common import fileutils
@@ -82,3 +84,51 @@ class TestCachedFile(utils.BaseTestCase):
         fresh, data = fileutils.read_cached_file("/this/is/a/fake")
         self.assertEqual(data, fake_contents)
         self.assertTrue(fresh)
+
+
+class DeleteIfExists(utils.BaseTestCase):
+    def test_file_present(self):
+        tmpfile = tempfile.mktemp()
+
+        open(tmpfile, 'w')
+        fileutils.delete_if_exists(tmpfile)
+        self.assertFalse(os.path.exists(tmpfile))
+
+    def test_file_absent(self):
+        tmpfile = tempfile.mktemp()
+
+        fileutils.delete_if_exists(tmpfile)
+        self.assertFalse(os.path.exists(tmpfile))
+
+    @mock.patch('os.unlink')
+    def test_file_error(self, osunlink):
+        tmpfile = tempfile.mktemp()
+
+        open(tmpfile, 'w')
+
+        error = OSError()
+        error.errno = errno.EINVAL
+        osunlink.side_effect = error
+
+        self.assertRaises(OSError, fileutils.delete_if_exists, tmpfile)
+
+
+class RemovePathOnError(utils.BaseTestCase):
+    def test_error(self):
+        tmpfile = tempfile.mktemp()
+        open(tmpfile, 'w')
+
+        try:
+            with fileutils.remove_path_on_error(tmpfile):
+                raise Exception
+        except Exception:
+            self.assertFalse(os.path.exists(tmpfile))
+
+    def test_no_error(self):
+        tmpfile = tempfile.mktemp()
+        open(tmpfile, 'w')
+
+        with fileutils.remove_path_on_error(tmpfile):
+            pass
+        self.assertTrue(os.path.exists(tmpfile))
+        os.unlink(tmpfile)