/usr/share/pyshared/genshi/template/base.py is in python-genshi 0.6-2.
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#
# Copyright (C) 2006-2010 Edgewall Software
# All rights reserved.
#
# This software is licensed as described in the file COPYING, which
# you should have received as part of this distribution. The terms
# are also available at http://genshi.edgewall.org/wiki/License.
#
# This software consists of voluntary contributions made by many
# individuals. For the exact contribution history, see the revision
# history and logs, available at http://genshi.edgewall.org/log/.
"""Basic templating functionality."""
from collections import deque
import os
from StringIO import StringIO
import sys
from genshi.core import Attrs, Stream, StreamEventKind, START, TEXT, _ensure
from genshi.input import ParseError
__all__ = ['Context', 'DirectiveFactory', 'Template', 'TemplateError',
'TemplateRuntimeError', 'TemplateSyntaxError', 'BadDirectiveError']
__docformat__ = 'restructuredtext en'
class TemplateError(Exception):
"""Base exception class for errors related to template processing."""
def __init__(self, message, filename=None, lineno=-1, offset=-1):
"""Create the exception.
:param message: the error message
:param filename: the filename of the template
:param lineno: the number of line in the template at which the error
occurred
:param offset: the column number at which the error occurred
"""
if filename is None:
filename = '<string>'
self.msg = message #: the error message string
if filename != '<string>' or lineno >= 0:
message = '%s (%s, line %d)' % (self.msg, filename, lineno)
Exception.__init__(self, message)
self.filename = filename #: the name of the template file
self.lineno = lineno #: the number of the line containing the error
self.offset = offset #: the offset on the line
class TemplateSyntaxError(TemplateError):
"""Exception raised when an expression in a template causes a Python syntax
error, or the template is not well-formed.
"""
def __init__(self, message, filename=None, lineno=-1, offset=-1):
"""Create the exception
:param message: the error message
:param filename: the filename of the template
:param lineno: the number of line in the template at which the error
occurred
:param offset: the column number at which the error occurred
"""
if isinstance(message, SyntaxError) and message.lineno is not None:
message = str(message).replace(' (line %d)' % message.lineno, '')
TemplateError.__init__(self, message, filename, lineno)
class BadDirectiveError(TemplateSyntaxError):
"""Exception raised when an unknown directive is encountered when parsing
a template.
An unknown directive is any attribute using the namespace for directives,
with a local name that doesn't match any registered directive.
"""
def __init__(self, name, filename=None, lineno=-1):
"""Create the exception
:param name: the name of the directive
:param filename: the filename of the template
:param lineno: the number of line in the template at which the error
occurred
"""
TemplateSyntaxError.__init__(self, 'bad directive "%s"' % name,
filename, lineno)
class TemplateRuntimeError(TemplateError):
"""Exception raised when an the evaluation of a Python expression in a
template causes an error.
"""
class Context(object):
"""Container for template input data.
A context provides a stack of scopes (represented by dictionaries).
Template directives such as loops can push a new scope on the stack with
data that should only be available inside the loop. When the loop
terminates, that scope can get popped off the stack again.
>>> ctxt = Context(one='foo', other=1)
>>> ctxt.get('one')
'foo'
>>> ctxt.get('other')
1
>>> ctxt.push(dict(one='frost'))
>>> ctxt.get('one')
'frost'
>>> ctxt.get('other')
1
>>> ctxt.pop()
{'one': 'frost'}
>>> ctxt.get('one')
'foo'
"""
def __init__(self, **data):
"""Initialize the template context with the given keyword arguments as
data.
"""
self.frames = deque([data])
self.pop = self.frames.popleft
self.push = self.frames.appendleft
self._match_templates = []
self._choice_stack = []
# Helper functions for use in expressions
def defined(name):
"""Return whether a variable with the specified name exists in the
expression scope."""
return name in self
def value_of(name, default=None):
"""If a variable of the specified name is defined, return its value.
Otherwise, return the provided default value, or ``None``."""
return self.get(name, default)
data.setdefault('defined', defined)
data.setdefault('value_of', value_of)
def __repr__(self):
return repr(list(self.frames))
def __contains__(self, key):
"""Return whether a variable exists in any of the scopes.
:param key: the name of the variable
"""
return self._find(key)[1] is not None
has_key = __contains__
def __delitem__(self, key):
"""Remove a variable from all scopes.
:param key: the name of the variable
"""
for frame in self.frames:
if key in frame:
del frame[key]
def __getitem__(self, key):
"""Get a variables's value, starting at the current scope and going
upward.
:param key: the name of the variable
:return: the variable value
:raises KeyError: if the requested variable wasn't found in any scope
"""
value, frame = self._find(key)
if frame is None:
raise KeyError(key)
return value
def __len__(self):
"""Return the number of distinctly named variables in the context.
:return: the number of variables in the context
"""
return len(self.items())
def __setitem__(self, key, value):
"""Set a variable in the current scope.
:param key: the name of the variable
:param value: the variable value
"""
self.frames[0][key] = value
def _find(self, key, default=None):
"""Retrieve a given variable's value and the frame it was found in.
Intended primarily for internal use by directives.
:param key: the name of the variable
:param default: the default value to return when the variable is not
found
"""
for frame in self.frames:
if key in frame:
return frame[key], frame
return default, None
def get(self, key, default=None):
"""Get a variable's value, starting at the current scope and going
upward.
:param key: the name of the variable
:param default: the default value to return when the variable is not
found
"""
for frame in self.frames:
if key in frame:
return frame[key]
return default
def keys(self):
"""Return the name of all variables in the context.
:return: a list of variable names
"""
keys = []
for frame in self.frames:
keys += [key for key in frame if key not in keys]
return keys
def items(self):
"""Return a list of ``(name, value)`` tuples for all variables in the
context.
:return: a list of variables
"""
return [(key, self.get(key)) for key in self.keys()]
def update(self, mapping):
"""Update the context from the mapping provided."""
self.frames[0].update(mapping)
def push(self, data):
"""Push a new scope on the stack.
:param data: the data dictionary to push on the context stack.
"""
def pop(self):
"""Pop the top-most scope from the stack."""
def _apply_directives(stream, directives, ctxt, vars):
"""Apply the given directives to the stream.
:param stream: the stream the directives should be applied to
:param directives: the list of directives to apply
:param ctxt: the `Context`
:param vars: additional variables that should be available when Python
code is executed
:return: the stream with the given directives applied
"""
if directives:
stream = directives[0](iter(stream), directives[1:], ctxt, **vars)
return stream
def _eval_expr(expr, ctxt, vars=None):
"""Evaluate the given `Expression` object.
:param expr: the expression to evaluate
:param ctxt: the `Context`
:param vars: additional variables that should be available to the
expression
:return: the result of the evaluation
"""
if vars:
ctxt.push(vars)
retval = expr.evaluate(ctxt)
if vars:
ctxt.pop()
return retval
def _exec_suite(suite, ctxt, vars=None):
"""Execute the given `Suite` object.
:param suite: the code suite to execute
:param ctxt: the `Context`
:param vars: additional variables that should be available to the
code
"""
if vars:
ctxt.push(vars)
ctxt.push({})
suite.execute(ctxt)
if vars:
top = ctxt.pop()
ctxt.pop()
ctxt.frames[0].update(top)
class DirectiveFactoryMeta(type):
"""Meta class for directive factories."""
def __new__(cls, name, bases, d):
if 'directives' in d:
d['_dir_by_name'] = dict(d['directives'])
d['_dir_order'] = [directive[1] for directive in d['directives']]
return type.__new__(cls, name, bases, d)
class DirectiveFactory(object):
"""Base for classes that provide a set of template directives.
:since: version 0.6
"""
__metaclass__ = DirectiveFactoryMeta
directives = []
"""A list of ``(name, cls)`` tuples that define the set of directives
provided by this factory.
"""
def get_directive(self, name):
"""Return the directive class for the given name.
:param name: the directive name as used in the template
:return: the directive class
:see: `Directive`
"""
return self._dir_by_name.get(name)
def get_directive_index(self, dir_cls):
"""Return a key for the given directive class that should be used to
sort it among other directives on the same `SUB` event.
The default implementation simply returns the index of the directive in
the `directives` list.
:param dir_cls: the directive class
:return: the sort key
"""
if dir_cls in self._dir_order:
return self._dir_order.index(dir_cls)
return len(self._dir_order)
class Template(DirectiveFactory):
"""Abstract template base class.
This class implements most of the template processing model, but does not
specify the syntax of templates.
"""
EXEC = StreamEventKind('EXEC')
"""Stream event kind representing a Python code suite to execute."""
EXPR = StreamEventKind('EXPR')
"""Stream event kind representing a Python expression."""
INCLUDE = StreamEventKind('INCLUDE')
"""Stream event kind representing the inclusion of another template."""
SUB = StreamEventKind('SUB')
"""Stream event kind representing a nested stream to which one or more
directives should be applied.
"""
serializer = None
_number_conv = unicode # function used to convert numbers to event data
def __init__(self, source, filepath=None, filename=None, loader=None,
encoding=None, lookup='strict', allow_exec=True):
"""Initialize a template from either a string, a file-like object, or
an already parsed markup stream.
:param source: a string, file-like object, or markup stream to read the
template from
:param filepath: the absolute path to the template file
:param filename: the path to the template file relative to the search
path
:param loader: the `TemplateLoader` to use for loading included
templates
:param encoding: the encoding of the `source`
:param lookup: the variable lookup mechanism; either "strict" (the
default), "lenient", or a custom lookup class
:param allow_exec: whether Python code blocks in templates should be
allowed
:note: Changed in 0.5: Added the `allow_exec` argument
"""
self.filepath = filepath or filename
self.filename = filename
self.loader = loader
self.lookup = lookup
self.allow_exec = allow_exec
self._init_filters()
self._init_loader()
self._prepared = False
if isinstance(source, basestring):
source = StringIO(source)
else:
source = source
try:
self._stream = self._parse(source, encoding)
except ParseError, e:
raise TemplateSyntaxError(e.msg, self.filepath, e.lineno, e.offset)
def __getstate__(self):
state = self.__dict__.copy()
state['filters'] = []
return state
def __setstate__(self, state):
self.__dict__ = state
self._init_filters()
def __repr__(self):
return '<%s "%s">' % (type(self).__name__, self.filename)
def _init_filters(self):
self.filters = [self._flatten, self._include]
def _init_loader(self):
if self.loader is None:
from genshi.template.loader import TemplateLoader
if self.filename:
if self.filepath != self.filename:
basedir = os.path.normpath(self.filepath)[:-len(
os.path.normpath(self.filename))
]
else:
basedir = os.path.dirname(self.filename)
else:
basedir = '.'
self.loader = TemplateLoader([os.path.abspath(basedir)])
@property
def stream(self):
if not self._prepared:
self._stream = list(self._prepare(self._stream))
self._prepared = True
return self._stream
def _parse(self, source, encoding):
"""Parse the template.
The parsing stage parses the template and constructs a list of
directives that will be executed in the render stage. The input is
split up into literal output (text that does not depend on the context
data) and directives or expressions.
:param source: a file-like object containing the XML source of the
template, or an XML event stream
:param encoding: the encoding of the `source`
"""
raise NotImplementedError
def _prepare(self, stream):
"""Call the `attach` method of every directive found in the template.
:param stream: the event stream of the template
"""
from genshi.template.loader import TemplateNotFound
for kind, data, pos in stream:
if kind is SUB:
directives = []
substream = data[1]
for _, cls, value, namespaces, pos in sorted(data[0]):
directive, substream = cls.attach(self, substream, value,
namespaces, pos)
if directive:
directives.append(directive)
substream = self._prepare(substream)
if directives:
yield kind, (directives, list(substream)), pos
else:
for event in substream:
yield event
else:
if kind is INCLUDE:
href, cls, fallback = data
if isinstance(href, basestring) and \
not getattr(self.loader, 'auto_reload', True):
# If the path to the included template is static, and
# auto-reloading is disabled on the template loader,
# the template is inlined into the stream
try:
tmpl = self.loader.load(href, relative_to=pos[0],
cls=cls or self.__class__)
for event in tmpl.stream:
yield event
except TemplateNotFound:
if fallback is None:
raise
for event in self._prepare(fallback):
yield event
continue
elif fallback:
# Otherwise the include is performed at run time
data = href, cls, list(self._prepare(fallback))
yield kind, data, pos
def generate(self, *args, **kwargs):
"""Apply the template to the given context data.
Any keyword arguments are made available to the template as context
data.
Only one positional argument is accepted: if it is provided, it must be
an instance of the `Context` class, and keyword arguments are ignored.
This calling style is used for internal processing.
:return: a markup event stream representing the result of applying
the template to the context data.
"""
vars = {}
if args:
assert len(args) == 1
ctxt = args[0]
if ctxt is None:
ctxt = Context(**kwargs)
else:
vars = kwargs
assert isinstance(ctxt, Context)
else:
ctxt = Context(**kwargs)
stream = self.stream
for filter_ in self.filters:
stream = filter_(iter(stream), ctxt, **vars)
return Stream(stream, self.serializer)
def _flatten(self, stream, ctxt, **vars):
number_conv = self._number_conv
stack = []
push = stack.append
pop = stack.pop
stream = iter(stream)
while 1:
for kind, data, pos in stream:
if kind is START and data[1]:
# Attributes may still contain expressions in start tags at
# this point, so do some evaluation
tag, attrs = data
new_attrs = []
for name, value in attrs:
if type(value) is list: # this is an interpolated string
values = [event[1]
for event in self._flatten(value, ctxt, **vars)
if event[0] is TEXT and event[1] is not None
]
if not values:
continue
value = ''.join(values)
new_attrs.append((name, value))
yield kind, (tag, Attrs(new_attrs)), pos
elif kind is EXPR:
result = _eval_expr(data, ctxt, vars)
if result is not None:
# First check for a string, otherwise the iterable test
# below succeeds, and the string will be chopped up into
# individual characters
if isinstance(result, basestring):
yield TEXT, result, pos
elif isinstance(result, (int, float, long)):
yield TEXT, number_conv(result), pos
elif hasattr(result, '__iter__'):
push(stream)
stream = _ensure(result)
break
else:
yield TEXT, unicode(result), pos
elif kind is SUB:
# This event is a list of directives and a list of nested
# events to which those directives should be applied
push(stream)
stream = _apply_directives(data[1], data[0], ctxt, vars)
break
elif kind is EXEC:
_exec_suite(data, ctxt, vars)
else:
yield kind, data, pos
else:
if not stack:
break
stream = pop()
def _include(self, stream, ctxt, **vars):
"""Internal stream filter that performs inclusion of external
template files.
"""
from genshi.template.loader import TemplateNotFound
for event in stream:
if event[0] is INCLUDE:
href, cls, fallback = event[1]
if not isinstance(href, basestring):
parts = []
for subkind, subdata, subpos in self._flatten(href, ctxt,
**vars):
if subkind is TEXT:
parts.append(subdata)
href = ''.join([x for x in parts if x is not None])
try:
tmpl = self.loader.load(href, relative_to=event[2][0],
cls=cls or self.__class__)
for event in tmpl.generate(ctxt, **vars):
yield event
except TemplateNotFound:
if fallback is None:
raise
for filter_ in self.filters:
fallback = filter_(iter(fallback), ctxt, **vars)
for event in fallback:
yield event
else:
yield event
EXEC = Template.EXEC
EXPR = Template.EXPR
INCLUDE = Template.INCLUDE
SUB = Template.SUB
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