plugin_registry/format/filter: new way of "private plugin" marking

using MetaPlugin class in the inheritance hierarchy to mark this
fact.

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

4 files changed, 29 insertions, 20 deletions

diff --git a/filter.py b/filter.py
index 17d8559..23f1598 100644
--- a/filter.py
+++ b/filter.py
@@ -13,7 +13,7 @@ from collections import OrderedDict, defaultdict
 from lxml import etree
 
 from .error import ClufterError
-from .plugin_registry import PluginRegistry
+from .plugin_registry import MetaPlugin, PluginRegistry
 from .utils import head_tail, hybridproperty, filtervarspop
 from .command_context import CommandContext
 
@@ -102,7 +102,7 @@ def tag_log(s, elem):
     return s.format(elem.tag, ', '.join(':'.join(i) for i in elem.items()))
 
 
-class XMLFilter(Filter):
+class XMLFilter(Filter, MetaPlugin):
     @staticmethod
     def _traverse(in_fmt, walk, walk_default=None, et=None,
                   preprocess=lambda s, n, r: s, proceed=lambda *x: x,
diff --git a/format.py b/format.py
index 843b658..5249fb2 100644
--- a/format.py
+++ b/format.py
@@ -17,7 +17,7 @@ from sys import modules
 from lxml import etree
 
 from .error import ClufterError
-from .plugin_registry import PluginRegistry
+from .plugin_registry import MetaPlugin, PluginRegistry
 from .utils import classproperty
 
 log = logging.getLogger(__name__)
@@ -30,8 +30,6 @@ class FormatError(ClufterError):
 
 class formats(PluginRegistry):
     """Format registry (to be used as a metaclass for formats)"""
-    use_local = True
-
     def __init__(cls, name, bases, attrs):
         cls._protocols = {}
         # protocols merge: top-down through inheritance
@@ -154,6 +152,11 @@ class Format(object):
 
     ####
 
+    native_protocol = 'to-be-defined-in-subclasses'
+
+
+class SimpleFormat(Format, MetaPlugin):
+    """This is what most of the format classes want to subclass"""
     native_protocol = 'bytestring'
 
     @producing('bytestring')
@@ -169,7 +172,7 @@ class Format(object):
         return filename
 
 
-class CompositeFormat(Format):
+class CompositeFormat(Format, MetaPlugin):
     """Quasi-format to stand in place of multiple formats at once
 
     It is intended to build on top of atomic formats (and only these,
@@ -180,7 +183,13 @@ class CompositeFormat(Format):
     contained/designated format in isolation, whereas the aggregated
     result is then returned.
 
-    See also: Format
+    Note that the semantics implicitly require protocols prescribing
+    the `CompositeFormat` instantiation to also become "composite",
+    i.e., having form like ('composite', ('file', 'file')) instead
+    of mere scalar like 'file' (IOW, whole declaration remains
+    fully "typed").
+
+    See also: Format, SimpleFormat
     """
     native_protocol = 'composite'  # to be overridden by per-instance one
                                    # XXX: hybridproperty?
@@ -220,7 +229,7 @@ class CompositeFormat(Format):
                      for f, p, a in zip(self._designed, protocol[1], args))
 
 
-class XML(Format):
+class XML(SimpleFormat):
     """"Base for XML-based configuration formats"""
     @classproperty
     def root(self):
diff --git a/formats/simpleconfig.py b/formats/simpleconfig.py
index 436c8fa..72acd3f 100644
--- a/formats/simpleconfig.py
+++ b/formats/simpleconfig.py
@@ -1,14 +1,14 @@
 # -*- coding: UTF-8 -*-
-# Copyright 2013 Red Hat, Inc.
+# Copyright 2014 Red Hat, Inc.
 # Part of clufter project
 # Licensed under GPLv2 (a copy included | http://gnu.org/licenses/gpl-2.0.txt)
 """Structured configuration formats such as corosync.conf"""
 __author__ = "Jan Pokorný <jpokorny @at@ Red Hat .dot. com>"
 
-from ..format import Format, producing
+from ..format import SimpleFormat
 
 
-class simpleconfig(Format):
+class simpleconfig(SimpleFormat):
     """"Structured configuration formats such as corosync.conf"""
     # yacc-based parser in fence-virt
     native_protocol = 'struct'
diff --git a/plugin_registry.py b/plugin_registry.py
index b7e43ab..59a0624 100644
--- a/plugin_registry.py
+++ b/plugin_registry.py
@@ -1,5 +1,5 @@
 # -*- coding: UTF-8 -*-
-# Copyright 2013 Red Hat, Inc.
+# Copyright 2014 Red Hat, Inc.
 # Part of clufter project
 # Licensed under GPLv2 (a copy included | http://gnu.org/licenses/gpl-2.0.txt)
 """Easy (at least for usage) plugin framework"""
@@ -17,6 +17,10 @@ from .utils import classproperty, hybridproperty
 log = logging.getLogger(__name__)
 
 
+class MetaPlugin(object):
+    """For use in the internal meta-hierarchy as "do not register me" mark"""
+
+
 class PluginRegistry(type):
     """Core of simple plugin framework
 
@@ -40,8 +44,7 @@ class PluginRegistry(type):
     # non-API
 
     def __new__(registry, name, bases, attrs):
-        if '__metaclass__' not in attrs and (registry.use_local
-          or not registry.__module__.startswith(attrs['__module__'])):
+        if '__metaclass__' not in attrs and MetaPlugin not in bases:
             # alleged end-use plugin
             ret = registry.probe(name, bases, attrs)
         else:
@@ -143,8 +146,6 @@ class PluginRegistry(type):
 
     # API
 
-    use_local = False
-
     @classmethod
     def setup(registry, reset=False):
         """Implicit setup upon first registry involvement or external reset"""
@@ -186,10 +187,9 @@ class PluginRegistry(type):
 
             # filled as a side-effect of meta-magic, see `__new__`
             ret.update((n, registry._plugins[n]) for n in path_plugins)
-            if registry.use_local:
-                # add "built-in" ones
-                ret.update((n, p) for n, p in registry._plugins.iteritems()
-                           if p.__module__ == registry.__module__)
+            # add "built-in" ones
+            ret.update((n, p) for n, p in registry._plugins.iteritems()
+                       if MetaPlugin not in p.__bases__)
 
         return ret