An adapter from IStorage to IMultiCommitStorage

This is currently used to run tests in traditional mode and in
IMultiCommitStorage mode using adapted file storages.

It might be useful later to adapt legacy storages.

src/ZODB/multicommitadapter.py

@@ -0,0 +1,65 @@
+"""Adapt non-IMultiCommitStorage storages to IMultiCommitStorage
+"""
+
+import zope.interface
+
+from .interfaces import IMultiCommitStorage
+from .ConflictResolution import ResolvedSerial
+
+@zope.interface.implementer(IMultiCommitStorage)
+class MultiCommitAdapter:
+
+    def __init__(self, storage):
+        self._storage = storage
+        ifaces = zope.interface.providedBy(storage)
+        assert IMultiCommitStorage not in ifaces
+        zope.interface.alsoProvides(self, ifaces)
+        self._resolved = set()
+
+    def __getattr__(self, name):
+        v = getattr(self._storage, name)
+        self.__dict__[name] = v
+        return v
+
+    def tpc_begin(self, *args):
+        self._storage.tpc_begin(*args)
+        self._resolved = set()
+
+    def store(self, oid, *args):
+        if self._storage.store(oid, *args) == ResolvedSerial:
+            self._resolved.add(oid)
+
+    def storeBlob(self, oid, *args):
+        s = self._storage.storeBlob(oid, *args)
+        if s:
+            if isinstance(s, bytes):
+                s = ((oid, s), )
+
+            for oid, serial in s:
+                if s == ResolvedSerial:
+                    self._resolved.add(oid)
+
+    def undo(self, transaction_id, transaction):
+        r = self._storage.undo(transaction_id, transaction)
+        if r:
+            self._resolved.update(set(r[1]))
+
+    def tpc_vote(self, *args):
+        s = self._storage.tpc_vote(*args)
+        for (oid, serial) in (s or ()):
+            if serial == ResolvedSerial:
+                self._resolved.add(oid)
+
+        return list(self._resolved)
+
+    def tpc_finish(self, transaction, f=lambda tid: None):
+
+        t = []
+
+        def func(tid):
+            t.append(tid)
+            f(tid)
+
+        self._storage.tpc_finish(transaction, func)
+
+        return t[0]