If one lock fails, do not lock anything

Or rather, unlock the ones we already locked.

2 files changed, 15 insertions, 1 deletions

diff --git a/obnamlib/lockmgr.py b/obnamlib/lockmgr.py
index 934f27ab..23c7a594 100644
--- a/obnamlib/lockmgr.py
+++ b/obnamlib/lockmgr.py
@@ -54,8 +54,15 @@ class LockManager(object):
         
     def lock(self, dirnames):
         '''Lock ALL the directories.'''
+        we_locked = []
         for dirname in dirnames:
-            self._lock_one(dirname)
+            try:
+                self._lock_one(dirname)
+            except obnamlib.LockFail:
+                self.unlock(we_locked)
+                raise
+            else:
+                we_locked.append(dirname)
 
     def unlock(self, dirnames):
         '''Unlock ALL the directories.'''
diff --git a/obnamlib/lockmgr_tests.py b/obnamlib/lockmgr_tests.py
index 26652899..8fbc52a9 100644
--- a/obnamlib/lockmgr_tests.py
+++ b/obnamlib/lockmgr_tests.py
@@ -84,3 +84,10 @@ class LockManagerTests(unittest.TestCase):
         for dirname in self.dirnames:
             self.assertFalse(self.locked(dirname))
 
+    def test_does_not_lock_anything_if_one_lock_fails(self):
+        self.lm.lock([self.dirnames[-1]])
+        self.assertRaises(obnamlib.LockFail, self.lm.lock, self.dirnames)
+        for dirname in self.dirnames[:-1]:
+            self.assertFalse(self.locked(dirname))
+        self.assertTrue(self.locked(self.dirnames[-1]))
+