Updated DemoStorage ZConfig support.

src/ZODB/DemoStorage.test

@@ -278,3 +278,52 @@ storage wrapped around it when necessary:
    >>> import os
    >>> os.path.exists(blobdir)
    False
+
+ZConfig support
+===============
+
+You can configure demo storages using ZConfig, using name, changes,
+and base options:
+
+    >>> import ZODB.config
+    >>> storage = ZODB.config.storageFromString("""
+    ... <demostorage>
+    ... </demostorage>
+    ... """)
+    >>> storage.getName()
+    "DemoStorage('MappingStorage', 'MappingStorage')"
+
+    >>> storage = ZODB.config.storageFromString("""
+    ... <demostorage>
+    ...    <filestorage base>
+    ...       path base.fs
+    ...    </filestorage>
+    ...
+    ...    <filestorage changes>
+    ...       path changes.fs
+    ...    </filestorage>
+    ... </demostorage>
+    ... """)
+    >>> storage.getName()
+    "DemoStorage('base.fs', 'changes.fs')"
+
+    >>> storage.close()
+
+    >>> storage = ZODB.config.storageFromString("""
+    ... <demostorage>
+    ...    name bob
+    ...    <filestorage>
+    ...       path base.fs
+    ...    </filestorage>
+    ...
+    ...    <filestorage changes>
+    ...       path changes.fs
+    ...    </filestorage>
+    ... </demostorage>
+    ... """)
+    >>> storage.getName()
+    'bob'
+    >>> storage.base.getName()
+    'base.fs'
+
+    >>> storage.close()

src/ZODB/component.xml

@@ -175,8 +175,7 @@
   <sectiontype name="demostorage" datatype=".DemoStorage"
                implements="ZODB.storage">
     <key name="name" />
-    <section type="ZODB.storage" name="*" attribute="base" />
-    <section type="ZODB.storage" name="changes" attribute="changes" />
+    <multisection type="ZODB.storage" name="*" attribute="factories" />
   </sectiontype>
 
 

src/ZODB/config.py

@@ -120,15 +120,17 @@ class MappingStorage(BaseConfig):
 class DemoStorage(BaseConfig):
 
     def open(self):
+        base = changes = None
+        for factory in self.config.factories:
+            if factory.name == 'changes':
+                changes = factory.open()
+            else:
+                if base is None:
+                    base = factory.open()
+                else:
+                    raise ValueError("Too many base storages defined!")
+        
         from ZODB.DemoStorage import DemoStorage
-        if self.config.base:
-            base = self.config.base.open()
-        else:
-            base = None
-        if self.config.changes:
-            changes = self.config.changes.open()
-        else:
-            changes = None
         return DemoStorage(self.config.name, base=base, changes=changes)
 
 class FileStorage(BaseConfig):