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""" The CfgGenshiGenerator allows you to use the `Genshi
<http://genshi.edgewall.org>`_ 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.base import TemplateError
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()
d['a']"""
try:
Suite(code).execute(dict())
except KeyError:
line = traceback.extract_tb(sys.exc_info()[2])[-1][1]
if line == 2:
return True
else:
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
class CfgGenshiGenerator(CfgGenerator):
""" The CfgGenshiGenerator allows you to use the `Genshi
<http://genshi.edgewall.org>`_ 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__
def get_data(self, entry, metadata):
if self.template is None:
raise PluginExecutionError("Failed to load template %s" %
self.name)
stream = self.template.generate(
**get_template_data(
entry, metadata, self.name,
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] == self.name:
raise PluginExecutionError("%s: %s at '%s'" %
(err.__class__.__name__, err,
quad[2]))
raise
except:
# this needs to be a blanket except, since it can catch
# any error raised by the genshi template.
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] == self.name:
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 self.template.stream
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 = match.group(0)
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
def handle_event(self, event):
CfgGenerator.handle_event(self, event)
try:
self.template = self.loader.load(
self.name, cls=NewTextTemplate,
encoding=Bcfg2.Options.setup.encoding)
except TemplateError:
raise PluginExecutionError("Failed to load template: %s" %
sys.exc_info()[1])
handle_event.__doc__ = CfgGenerator.handle_event.__doc__
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