Plugins: Added TemplateDataProvider plugin interface

This lets you provide variables to the top-level namespace of
templates in a more seamless way than through a Connector plugin.
It's mostly useful for TemplateHelper for now, but may find other uses
in the future.

3 files changed, 79 insertions, 26 deletions

diff --git a/src/lib/Bcfg2/Server/Plugins/Cfg/CfgCheetahGenerator.py b/src/lib/Bcfg2/Server/Plugins/Cfg/CfgCheetahGenerator.py
index 476dc1fc6..84309b5dd 100644
--- a/src/lib/Bcfg2/Server/Plugins/Cfg/CfgCheetahGenerator.py
+++ b/src/lib/Bcfg2/Server/Plugins/Cfg/CfgCheetahGenerator.py
@@ -3,7 +3,8 @@
 :ref:`server-plugins-generators-cfg` files. """
 
 import Bcfg2.Options
-from Bcfg2.Server.Plugin import PluginExecutionError
+from Bcfg2.Server.Plugin import PluginExecutionError, \
+    DefaultTemplateDataProvider, get_template_data
 from Bcfg2.Server.Plugins.Cfg import CfgGenerator
 
 try:
@@ -13,6 +14,18 @@ except ImportError:
     HAS_CHEETAH = False
 
 
+class DefaultCheetahDataProvider(DefaultTemplateDataProvider):
+    """ Template data provider for Cheetah templates. Cheetah and
+    Genshi currently differ over the value of the ``path`` variable,
+    which is why this is necessary. """
+
+    def get_template_data(self, entry, metadata, template):
+        rv = DefaultTemplateDataProvider.get_template_data(self, entry,
+                                                           metadata, template)
+        rv['path'] = rv['name']
+        return rv
+
+
 class CfgCheetahGenerator(CfgGenerator):
     """ The CfgCheetahGenerator allows you to use the `Cheetah
     <http://www.cheetahtemplate.org/>`_ templating system to generate
@@ -37,10 +50,9 @@ class CfgCheetahGenerator(CfgGenerator):
     def get_data(self, entry, metadata):
         template = Template(self.data.decode(Bcfg2.Options.setup.encoding),
                             compilerSettings=self.settings)
-        template.metadata = metadata
-        template.name = entry.get('realname', entry.get('name'))
-        template.path = entry.get('realname', entry.get('name'))
-        template.source_path = self.name
-        template.repo = Bcfg2.Options.setup.repository
+        for key, val in get_template_data(
+            entry, metadata, self.name,
+            default=DefaultCheetahDataProvider()).items():
+            setattr(template, key, val)
         return template.respond()
     get_data.__doc__ = CfgGenerator.get_data.__doc__
diff --git a/src/lib/Bcfg2/Server/Plugins/Cfg/CfgGenshiGenerator.py b/src/lib/Bcfg2/Server/Plugins/Cfg/CfgGenshiGenerator.py
index 7ba8c4491..ef4e6a656 100644
--- a/src/lib/Bcfg2/Server/Plugins/Cfg/CfgGenshiGenerator.py
+++ b/src/lib/Bcfg2/Server/Plugins/Cfg/CfgGenshiGenerator.py
@@ -6,7 +6,8 @@ import re
 import sys
 import traceback
 import Bcfg2.Options
-from Bcfg2.Server.Plugin import PluginExecutionError, removecomment
+from Bcfg2.Server.Plugin import PluginExecutionError, removecomment, \
+    DefaultTemplateDataProvider, get_template_data
 from Bcfg2.Server.Plugins.Cfg import CfgGenerator
 from genshi.template import TemplateLoader, NewTextTemplate
 from genshi.template.eval import UndefinedError, Suite
@@ -42,6 +43,18 @@ d['a']"""
 GENSHI_REMOVES_BLANK_LINES = _genshi_removes_blank_lines()
 
 
+class DefaultGenshiDataProvider(DefaultTemplateDataProvider):
+    """ Template data provider for Genshi templates. Cheetah and
+    Genshi currently differ over the value of the ``path`` variable,
+    which is why this is necessary. """
+
+    def get_template_data(self, entry, metadata, template):
+        rv = DefaultTemplateDataProvider.get_template_data(self, entry,
+                                                           metadata, template)
+        rv['path'] = template
+        return rv
+
+
 class CfgGenshiGenerator(CfgGenerator):
     """ The CfgGenshiGenerator allows you to use the `Genshi
     <http://genshi.edgewall.org>`_ templating system to generate
@@ -81,13 +94,10 @@ class CfgGenshiGenerator(CfgGenerator):
             raise PluginExecutionError("Failed to load template %s" %
                                        self.name)
 
-        fname = entry.get('realname', entry.get('name'))
         stream = self.template.generate(
-            name=fname,
-            metadata=metadata,
-            path=self.name,
-            source_path=self.name,
-            repo=Bcfg2.Options.setup.repository).filter(removecomment)
+            **get_template_data(
+                entry, metadata, self.name,
+                default=DefaultGenshiDataProvider())).filter(removecomment)
         try:
             try:
                 return stream.render('text',
diff --git a/src/lib/Bcfg2/Server/Plugins/TemplateHelper.py b/src/lib/Bcfg2/Server/Plugins/TemplateHelper.py
index 82d8bfae2..05b5086f9 100644
--- a/src/lib/Bcfg2/Server/Plugins/TemplateHelper.py
+++ b/src/lib/Bcfg2/Server/Plugins/TemplateHelper.py
@@ -3,11 +3,9 @@
 import re
 import imp
 import sys
-import logging
+from Bcfg2.Logger import Debuggable
 import Bcfg2.Server.Plugin
 
-LOGGER = logging.getLogger(__name__)
-
 MODULE_RE = re.compile(r'(?P<filename>(?P<module>[^\/]+)\.py)$')
 
 
@@ -19,10 +17,11 @@ def safe_module_name(module):
     return '__TemplateHelper_%s' % module
 
 
-class HelperModule(object):
+class HelperModule(Debuggable):
     """ Representation of a TemplateHelper module """
 
     def __init__(self, name):
+        Debuggable.__init__(self)
         self.name = name
 
         #: The name of the module as used by get_additional_data().
@@ -32,6 +31,9 @@ class HelperModule(object):
         #: The attributes exported by this module
         self._attrs = []
 
+        #: The attributes added to the template namespace by this module
+        self.defaults = []
+
     def HandleEvent(self, event=None):
         """ HandleEvent is called whenever the FAM registers an event.
 
@@ -47,37 +49,50 @@ class HelperModule(object):
                                      self.name)
         except:  # pylint: disable=W0702
             err = sys.exc_info()[1]
-            LOGGER.error("TemplateHelper: Failed to import %s: %s" %
-                         (self.name, err))
+            self.logger.error("TemplateHelper: Failed to import %s: %s" %
+                              (self.name, err))
             return
 
         if not hasattr(module, "__export__"):
-            LOGGER.error("TemplateHelper: %s has no __export__ list" %
-                         self.name)
+            self.logger.error("TemplateHelper: %s has no __export__ list" %
+                              self.name)
             return
 
         newattrs = []
         for sym in module.__export__:
             if sym not in self._attrs and hasattr(self, sym):
-                LOGGER.warning("TemplateHelper: %s: %s is a reserved keyword, "
-                               "skipping export" % (self.name, sym))
+                self.logger.warning(
+                    "TemplateHelper: %s: %s is a reserved keyword, "
+                    "skipping export" % (self.name, sym))
                 continue
             try:
                 setattr(self, sym, getattr(module, sym))
                 newattrs.append(sym)
             except AttributeError:
-                LOGGER.warning("TemplateHelper: %s exports %s, but has no "
-                               "such attribute" % (self.name, sym))
+                self.logger.warning(
+                    "TemplateHelper: %s exports %s, but has no such attribute"
+                    % (self.name, sym))
+
         # remove old exports
         for sym in set(self._attrs) - set(newattrs):
             delattr(self, sym)
 
         self._attrs = newattrs
 
+        self.defaults = []
+        for sym in getattr(module, "__default__", []):
+            if sym not in self._attrs:
+                self.logger.warning(
+                    "TemplateHelper: %s: %s is flagged as a default, "
+                    "but is not exported; skipping")
+                continue
+            self.defaults.append(sym)
+
 
 class TemplateHelper(Bcfg2.Server.Plugin.Plugin,
                      Bcfg2.Server.Plugin.Connector,
-                     Bcfg2.Server.Plugin.DirectoryBacked):
+                     Bcfg2.Server.Plugin.DirectoryBacked,
+                     Bcfg2.Server.Plugin.TemplateDataProvider):
     """ A plugin to provide helper classes and functions to templates """
     __author__ = 'chris.a.st.pierre@gmail.com'
     ignore = re.compile(r'^(\.#.*|.*~|\..*\.(sw[px])|.*\.py[co])$')
@@ -88,7 +103,23 @@ class TemplateHelper(Bcfg2.Server.Plugin.Plugin,
         Bcfg2.Server.Plugin.Plugin.__init__(self, core)
         Bcfg2.Server.Plugin.Connector.__init__(self)
         Bcfg2.Server.Plugin.DirectoryBacked.__init__(self, self.data)
+        Bcfg2.Server.Plugin.TemplateDataProvider.__init__(self)
 
     def get_additional_data(self, _):
         return dict([(h._module_name, h)  # pylint: disable=W0212
                      for h in self.entries.values()])
+
+    def get_template_data(self, *_):
+        rv = dict()
+        source = dict()
+        for helper in self.entries.values():
+            for key in helper.defaults:
+                if key not in rv:
+                    rv[key] = getattr(helper, key)
+                    source[key] = helper
+                else:
+                    self.logger.warning(
+                        "TemplateHelper: Duplicate default variable %s "
+                        "provided by both %s and %s" %
+                        (key, helper.name, source[key].name))
+        return rv