Fix the cleanup of uncommitted blob data under PyPy.

src/ZODB/blob.py

@@ -57,6 +57,15 @@ valid_modes = 'r', 'w', 'r+', 'a', 'c'
 # This introduces a threading issue, since a blob file may be destroyed
 # via GC in any thread.
 
+# PyPy 2.5 doesn't properly call the cleanup function
+# of a weakref when the weakref object dies at the same time
+# as the object it refers to. In other words, this doesn't work:
+#    self._ref = weakref.ref(self, lambda ref: ...)
+# because the function never gets called. The Blob class used
+# to use that pattern to clean up uncommitted files; now we use this
+# module-level global (but still keep a reference in the Blob in case
+# we need premature cleanup)
+_blob_close_refs = []
 
 @zope.interface.implementer(ZODB.interfaces.IBlob)
 class Blob(persistent.Persistent):
@@ -65,6 +74,7 @@ class Blob(persistent.Persistent):
 
     _p_blob_uncommitted = None  # Filename of the uncommitted (dirty) data
     _p_blob_committed = None    # Filename of the committed data
+    _p_blob_ref = None          # weakreference to self; also in _blob_close_refs
 
     readers = writers = None
 
@@ -283,8 +293,13 @@ class Blob(persistent.Persistent):
         def cleanup(ref):
             if os.path.exists(filename):
                 os.remove(filename)
-
+            try:
+                _blob_close_refs.remove(ref)
+            except ValueError:
+                pass
         self._p_blob_ref = weakref.ref(self, cleanup)
+        _blob_close_refs.append(self._p_blob_ref)
+
         return filename
 
     def _uncommitted(self):
@@ -293,6 +308,10 @@ class Blob(persistent.Persistent):
         filename = self._p_blob_uncommitted
         if filename is None and self._p_blob_committed is None:
             filename = self._create_uncommitted_file()
+        try:
+            _blob_close_refs.remove(self._p_blob_ref)
+        except ValueError:
+            pass
         self._p_blob_uncommitted = self._p_blob_ref = None
         return filename
 

src/ZODB/tests/blob_transaction.txt

@@ -79,7 +79,7 @@ resulting filehandle is accomplished via the filehandle's read method::
     >>> blob1afh1.read()
     'this is blob 1'
 
-Let's make another filehandle for read only to blob1a. Aach file
+Let's make another filehandle for read only to blob1a. Each file
 handle has a reference to the (same) underlying blob::
 
     >>> blob1afh2 = blob1a.open("r")

src/ZODB/tests/testblob.py

@@ -345,6 +345,18 @@ def gc_blob_removes_uncommitted_data():
     >>> os.path.exists(fname)
     True
     >>> file = blob = None
+
+    PyPy not being reference counted actually needs GC to be
+    explicitly requested. In experiments, it finds the weakref
+    on the first collection, but only does the cleanup on the second
+    collection:
+
+    >>> import gc
+    >>> _ = gc.collect()
+    >>> _ = gc.collect()
+
+    Now the file is gone on all platforms:
+
     >>> os.path.exists(fname)
     False
     """