Source code for Bcfg2.Server.Plugins.Cfg.CfgGenshiGenerator

""" The CfgGenshiGenerator allows you to use the `Genshi
<>`_ templating system to generate
:ref:`server-plugins-generators-cfg` files. """

import re
import sys
import traceback
import Bcfg2.Options
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

def _genshi_removes_blank_lines():
    """ Genshi 0.5 uses the Python :mod:`compiler` package to
    compile genshi snippets to AST.  Genshi 0.6 uses some bespoke
    magic, because compiler has been deprecated.
    :func:`compiler.parse` produces an AST that removes all excess
    whitespace (e.g., blank lines), while
    :func:`genshi.template.astutil.parse` does not.  In order to
    determine which actual line of code an error occurs on, we
    need to know which is in use and how it treats blank lines.
    I've beat my head against this for hours and the best/only way
    I can find is to compile some genshi code with an error and
    see which line it's on."""
    code = """d = dict()
    except KeyError:
        line = traceback.extract_tb(sys.exc_info()[2])[-1][1]
        if line == 2:
            return True
            return False

#: True if Genshi removes all blank lines from a code block before
#: executing it; False indicates that Genshi only removes leading
#: and trailing blank lines. See
#: :func:`_genshi_removes_blank_lines` for an explanation of this.
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

[docs]class CfgGenshiGenerator(CfgGenerator): """ The CfgGenshiGenerator allows you to use the `Genshi <>`_ templating system to generate :ref:`server-plugins-generators-cfg` files. """ #: Handle .genshi files __extensions__ = ['genshi'] #: ``__loader_cls__`` is the class that will be instantiated to #: load the template files. It must implement one public function, #: ``load()``, as :class:`genshi.template.TemplateLoader`. __loader_cls__ = TemplateLoader #: Ignore ``.genshi_include`` files so they can be used with the #: Genshi ``{% include ... %}`` directive without raising warnings. __ignore__ = ["genshi_include"] #: Low priority to avoid matching host- or group-specific #: .crypt.genshi files __priority__ = 50 #: Error-handling in Genshi is pretty obtuse. This regex is used #: to extract the first line of the code block that raised an #: exception in a Genshi template so we can provide a decent error #: message that actually tells the end user where an error #: occurred. pyerror_re = re.compile(r'<\w+ u?[\'"](.*?)\s*\.\.\.[\'"]>') def __init__(self, fname, spec): CfgGenerator.__init__(self, fname, spec) self.template = None self.loader = self.__loader_cls__(max_cache_size=0) __init__.__doc__ = CfgGenerator.__init__.__doc__
[docs] def get_data(self, entry, metadata): if self.template is None: raise PluginExecutionError("Failed to load template %s" % stream = self.template.generate( **get_template_data( entry, metadata,, default=DefaultGenshiDataProvider())).filter(removecomment) try: try: return stream.render('text', encoding=Bcfg2.Options.setup.encoding, strip_whitespace=False) except TypeError: return stream.render('text', encoding=Bcfg2.Options.setup.encoding) except UndefinedError: # a failure in a genshi expression _other_ than %{ python ... %} err = sys.exc_info()[1] stack = traceback.extract_tb(sys.exc_info()[2]) for quad in stack: if quad[0] == raise PluginExecutionError("%s: %s at '%s'" % (err.__class__.__name__, err, quad[2])) raise except: self._handle_genshi_exception(sys.exc_info())
get_data.__doc__ = CfgGenerator.get_data.__doc__ def _handle_genshi_exception(self, exc): """ this is horrible, and I deeply apologize to whoever gets to maintain this after I go to the Great Beer Garden in the Sky. genshi is incredibly opaque about what's being executed, so the only way I can find to determine which {% python %} block is being executed -- if there are multiples -- is to iterate through them and match the snippet of the first line that's in the traceback with the first non-empty line of the block. """ # a failure in a %{ python ... %} block -- the snippet in # the traceback is just the beginning of the block. err = exc[1] stack = traceback.extract_tb(exc[2]) # find the right frame of the stack for frame in reversed(stack): if frame[0] == lineno, func = frame[1:3] break else: # couldn't even find the stack frame, wtf. raise PluginExecutionError("%s: %s" % (err.__class__.__name__, err)) execs = [contents for etype, contents, _ in if etype == self.template.EXEC] contents = None if len(execs) == 1: contents = execs[0] elif len(execs) > 1: match = self.pyerror_re.match(func) if match: firstline = for pyblock in execs: if pyblock.startswith(firstline): contents = pyblock break # else, no EXEC blocks -- WTF? if contents: # we now have the bogus block, but we need to get the # offending line. To get there, we do (line number given # in the exception) - (firstlineno from the internal # genshi code object of the snippet) = (line number of the # line with an error within the block, with blank lines # removed as appropriate for # :attr:`GENSHI_REMOVES_BLANK_LINES`) code = contents.source.strip().splitlines() if GENSHI_REMOVES_BLANK_LINES: code = [l for l in code if l.strip()] try: line = code[lineno - contents.code.co_firstlineno] raise PluginExecutionError("%s: %s at '%s'" % (err.__class__.__name__, err, line)) except IndexError: raise PluginExecutionError("%s: %s" % (err.__class__.__name__, err)) raise
[docs] def handle_event(self, event): CfgGenerator.handle_event(self, event) try: self.template = \ self.loader.load(, cls=NewTextTemplate, encoding=Bcfg2.Options.setup.encoding) except: raise PluginExecutionError("Failed to load template: %s" % sys.exc_info()[1])
handle_event.__doc__ = CfgGenerator.handle_event.__doc__