Add FilesystemRegistry class and fix 'props' bug in constructors

src/zasd/filesystem.py

@@ -1,4 +1,6 @@
-filesystems = {}
+# Public API
+
+''' Base filesystem classes and registration facilities '''
 
 class Filesystem:
     ''' Base filsystem class inherited by each filesystem implementation '''
@@ -8,7 +10,7 @@ class Filesystem:
         self._name = name
 
         # Process arguments to extract all properties
-        props = process_args(props, kwprops)
+        props = _process_args(props, kwprops)
 
         # Delegate further initialisation to the subclass
         self.initialise(props)
@@ -45,7 +47,7 @@ class Filesystem:
 class Snapshot:
     ''' Base snapshot class inherited by each filesystem implementation '''
 
-    def __init__(self, filesystem, tag, *props, **kwprops):
+    def __init__(self, filesystem, tag, props, **kwprops):
         # pylint: disable=unused-argument
 
         # Set common properties
@@ -53,7 +55,7 @@ class Snapshot:
         self._tag = tag
 
         # Process arguments to extract all properties
-        props = process_args(props, kwprops)
+        props = _process_args(props, kwprops)
 
         # Delegate further initialisation to the subclass
         self.initialise(props)
@@ -96,7 +98,30 @@ class Snapshot:
         ''' Delete this snapshot. No further method calls are made on the
             snapshot once it has been destroyed. '''
 
-def process_args(props, kwprops):
+class FilesystemRegistry:
+    ''' Class that keeps a global registry of available Filesystem classes '''
+
+    _filesystems = {}
+
+    @classmethod
+    def register(cls, name, klass):
+        ''' Register a filesystem. If a filesystem needs to be configured by the
+            user, it must retrieve its configuration from a dictionary at
+            config['filesystems'][name]. '''
+        cls._filesystems[name] = klass
+
+    @classmethod
+    def all(cls):
+        ''' Retrieve a {name: class} dictionary of all registered
+            filesystems '''
+        return dict(cls._filesystems)
+
+#
+# Private objects
+
+_filesystems = {}
+
+def _process_args(props, kwprops):
     ''' Merge 'props' and 'kwprops' into single dictionary '''
     if props:
         if not isinstance(props, dict):
@@ -108,10 +133,4 @@ def process_args(props, kwprops):
     # Update properties dictionary with keyword arguments
     props.update(kwprops)
 
-    return props
-
-def register(name, klass):
-    ''' Register a filesystem. If a filesystem needs to be configured by the
-        user, it must retrieve its configuration from a dictionary at
-        config['filesystems'][name]. '''
-    filesystems[name] = klass
+    return props