command_context: introduce filters-global keyword-based config

It's up to command implementer to keep possible collisions away.

Signed-off-by: Jan Pokorný <jpokorny@redhat.com>

1 files changed, 27 insertions, 14 deletions

diff --git a/command_context.py b/command_context.py
index 72bad05..1e9df42 100644
--- a/command_context.py
+++ b/command_context.py
@@ -20,20 +20,22 @@ class CommandContextError(ClufterError):
 class CommandContextBase(MutableMapping):
     """Object representing command context"""
     def __init__(self, initial=None, parent=None):
-        if parent is None:
-            parent = self
-        self._parent = parent
         try:
-            self._dict = dict(initial)
+            self._dict = initial if type(initial) is dict else dict(initial)
         except TypeError:
             self._dict = {}
+        self._parent = parent if parent is not None else self
 
     def __delitem__(self, key):
         del self._dict[key]
 
     def __getitem__(self, key):
-        #return self._dict[key]
-        return self._dict.get(key)  # make it soft-error (->setdefault reimpl.)
+        try:
+            return self._dict[key]
+        except KeyError:
+            pass
+        # make it soft-error (->setdefault reimpl.)
+        return None if self._parent is self else self._parent[key]
 
     def setdefault(self, key, default=None):
         return self._dict.setdefault(key, default)
@@ -45,6 +47,7 @@ class CommandContextBase(MutableMapping):
         return len(self._dict)
 
     def __setitem__(self, key, value):
+        # XXX value could be also any valid dict constructor argument
         self._dict[key] = CommandContextBase(initial=value, parent=self) \
                           if isinstance(value, dict) else value
 
@@ -55,10 +58,15 @@ class CommandContextBase(MutableMapping):
 
 class CommandContext(CommandContextBase):
     def __init__(self, *args, **kwargs):
+        # filter_context ... where global arguments for filters to be stored
+        # filters        ... where filter instance + arguments hybrid is stored
         super(CommandContext, self).__init__(*args, **kwargs)
-        self._filters = {}
+        # could be cycle up to self if {} was used instead
+        self['__filter_context__'] = CommandContextBase()
+        self['__filters__'] = CommandContextBase()
 
-    def _wrapping_nested_context(self, obj):
+    @staticmethod
+    def _wrapping_nested_context(obj):
         class wrapped(CommandContextBase):
             def __getattribute__(self, name):
                 if name == 'ctxt_wrapped':
@@ -82,19 +90,24 @@ class CommandContext(CommandContextBase):
 
             def __setattribute__(self, name, value):
                 obj.__setattribute__(name, value)
-        return (wrapped(parent=self))
+        return wrapped
 
     def ensure_filter(self, flt):
-        existing, key = self._filters, flt.__class__.name
+        existing, key = self['__filters__'], flt.__class__.name
         ret = existing.get(key, None)
-        if ret:
+        if ret is not None:
             assert id(ret.ctxt_wrapped) == id(flt)
         else:
-            ret = existing[key] = self._wrapping_nested_context(flt)
+            ret = self._wrapping_nested_context(flt)
+            ret = existing[key] = ret(parent=self['__filter_context__'])
         return ret
 
     def ensure_filters(self, flts):
         return map(self.ensure_filter, flts)
 
-    def filter(self, which):
-        return self._filters[which]
+    def filter(self, which=None):
+        if which is not None:
+            ret = self['__filters__'][which]
+        else:
+            ret = self['__filter_context__']
+        return ret