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""" A plugin to provide helper classes and functions to templates """
import re
import imp
import sys
import lxml.etree
from Bcfg2.Server.Plugin import Plugin, Connector, DirectoryBacked, \
TemplateDataProvider, DefaultTemplateDataProvider
from Bcfg2.Logger import Debuggable
MODULE_RE = re.compile(r'(?P<filename>(?P<module>[^\/]+)\.py)$')
def safe_module_name(module):
""" Munge the name of a TemplateHelper module to avoid collisions
with other Python modules. E.g., if someone has a helper named
'ldap.py', it should not be added to ``sys.modules`` as ``ldap``,
but rather as something more obscure. """
return '__TemplateHelper_%s' % module
class HelperModule(Debuggable):
""" Representation of a TemplateHelper module """
def __init__(self, name, core):
Debuggable.__init__(self)
self.name = name
self.core = core
#: The name of the module as used by get_additional_data().
#: the name of the file with .py stripped off.
self._module_name = MODULE_RE.search(self.name).group('module')
#: The attributes exported by this module
self._attrs = []
#: The attributes added to the template namespace by this module
self.defaults = []
default_prov = DefaultTemplateDataProvider()
self.reserved_defaults = default_prov.get_template_data(
lxml.etree.Element("Path", name="/dummy"),
None, None).keys() + ["path"]
def HandleEvent(self, event=None):
""" HandleEvent is called whenever the FAM registers an event.
:param event: The event object
:type event: Bcfg2.Server.FileMonitor.Event
:returns: None
"""
if event and event.code2str() not in ['exists', 'changed', 'created']:
return
# expire the metadata cache, because the module might have changed
if self.core.metadata_cache_mode in ['cautious', 'aggressive']:
self.core.metadata_cache.expire()
try:
module = imp.load_source(safe_module_name(self._module_name),
self.name)
except: # pylint: disable=W0702
# this needs to be a blanket except because the
# imp.load_source() call can raise literally any error,
# since it imports the module and just passes through any
# exceptions raised.
err = sys.exc_info()[1]
self.logger.error("TemplateHelper: Failed to import %s: %s" %
(self.name, err))
return
if not hasattr(module, "__export__"):
self.logger.error("TemplateHelper: %s has no __export__ list" %
self.name)
return
newattrs = []
for sym in module.__export__ + getattr(module, "__default__", []):
if sym in newattrs:
# already added to attribute list
continue
if sym not in self._attrs and hasattr(self, 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:
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 in self.reserved_defaults:
self.logger.warning(
"TemplateHelper: %s: %s is a reserved keyword, not adding "
"as default" % (self.name, sym))
self.defaults.append(sym)
class TemplateHelper(Plugin, Connector, DirectoryBacked, 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])$')
patterns = MODULE_RE
def __init__(self, core):
Plugin.__init__(self, core)
Connector.__init__(self)
DirectoryBacked.__init__(self, self.data)
TemplateDataProvider.__init__(self)
# The HelperModule needs access to the core, so we have to construct
# it manually and add the custom argument.
self.__child__ = lambda fname: HelperModule(fname, core)
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
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