281 lines
8.8 KiB
Python
281 lines
8.8 KiB
Python
from contextlib import contextmanager
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from copy import copy
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# Hard-coded processor for easier use of CSRF protection.
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_builtin_context_processors = ('django.template.context_processors.csrf',)
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class ContextPopException(Exception):
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"pop() has been called more times than push()"
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pass
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class ContextDict(dict):
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def __init__(self, context, *args, **kwargs):
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super().__init__(*args, **kwargs)
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context.dicts.append(self)
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self.context = context
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def __enter__(self):
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return self
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def __exit__(self, *args, **kwargs):
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self.context.pop()
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class BaseContext:
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def __init__(self, dict_=None):
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self._reset_dicts(dict_)
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def _reset_dicts(self, value=None):
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builtins = {'True': True, 'False': False, 'None': None}
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self.dicts = [builtins]
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if value is not None:
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self.dicts.append(value)
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def __copy__(self):
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duplicate = copy(super())
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duplicate.dicts = self.dicts[:]
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return duplicate
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def __repr__(self):
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return repr(self.dicts)
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def __iter__(self):
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return reversed(self.dicts)
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def push(self, *args, **kwargs):
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dicts = []
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for d in args:
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if isinstance(d, BaseContext):
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dicts += d.dicts[1:]
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else:
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dicts.append(d)
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return ContextDict(self, *dicts, **kwargs)
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def pop(self):
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if len(self.dicts) == 1:
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raise ContextPopException
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return self.dicts.pop()
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def __setitem__(self, key, value):
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"Set a variable in the current context"
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self.dicts[-1][key] = value
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def set_upward(self, key, value):
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"""
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Set a variable in one of the higher contexts if it exists there,
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otherwise in the current context.
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"""
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context = self.dicts[-1]
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for d in reversed(self.dicts):
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if key in d:
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context = d
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break
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context[key] = value
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def __getitem__(self, key):
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"Get a variable's value, starting at the current context and going upward"
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for d in reversed(self.dicts):
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if key in d:
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return d[key]
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raise KeyError(key)
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def __delitem__(self, key):
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"Delete a variable from the current context"
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del self.dicts[-1][key]
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def __contains__(self, key):
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return any(key in d for d in self.dicts)
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def get(self, key, otherwise=None):
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for d in reversed(self.dicts):
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if key in d:
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return d[key]
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return otherwise
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def setdefault(self, key, default=None):
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try:
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return self[key]
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except KeyError:
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self[key] = default
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return default
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def new(self, values=None):
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"""
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Return a new context with the same properties, but with only the
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values given in 'values' stored.
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"""
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new_context = copy(self)
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new_context._reset_dicts(values)
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return new_context
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def flatten(self):
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"""
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Return self.dicts as one dictionary.
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"""
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flat = {}
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for d in self.dicts:
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flat.update(d)
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return flat
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def __eq__(self, other):
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"""
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Compare two contexts by comparing theirs 'dicts' attributes.
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"""
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return (
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isinstance(other, BaseContext) and
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# because dictionaries can be put in different order
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# we have to flatten them like in templates
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self.flatten() == other.flatten()
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)
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class Context(BaseContext):
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"A stack container for variable context"
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def __init__(self, dict_=None, autoescape=True, use_l10n=None, use_tz=None):
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self.autoescape = autoescape
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self.use_l10n = use_l10n
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self.use_tz = use_tz
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self.template_name = "unknown"
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self.render_context = RenderContext()
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# Set to the original template -- as opposed to extended or included
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# templates -- during rendering, see bind_template.
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self.template = None
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super().__init__(dict_)
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@contextmanager
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def bind_template(self, template):
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if self.template is not None:
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raise RuntimeError("Context is already bound to a template")
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self.template = template
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try:
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yield
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finally:
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self.template = None
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def __copy__(self):
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duplicate = super().__copy__()
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duplicate.render_context = copy(self.render_context)
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return duplicate
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def update(self, other_dict):
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"Push other_dict to the stack of dictionaries in the Context"
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if not hasattr(other_dict, '__getitem__'):
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raise TypeError('other_dict must be a mapping (dictionary-like) object.')
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if isinstance(other_dict, BaseContext):
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other_dict = other_dict.dicts[1:].pop()
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return ContextDict(self, other_dict)
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class RenderContext(BaseContext):
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"""
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A stack container for storing Template state.
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RenderContext simplifies the implementation of template Nodes by providing a
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safe place to store state between invocations of a node's `render` method.
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The RenderContext also provides scoping rules that are more sensible for
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'template local' variables. The render context stack is pushed before each
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template is rendered, creating a fresh scope with nothing in it. Name
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resolution fails if a variable is not found at the top of the RequestContext
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stack. Thus, variables are local to a specific template and don't affect the
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rendering of other templates as they would if they were stored in the normal
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template context.
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"""
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template = None
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def __iter__(self):
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yield from self.dicts[-1]
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def __contains__(self, key):
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return key in self.dicts[-1]
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def get(self, key, otherwise=None):
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return self.dicts[-1].get(key, otherwise)
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def __getitem__(self, key):
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return self.dicts[-1][key]
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@contextmanager
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def push_state(self, template, isolated_context=True):
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initial = self.template
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self.template = template
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if isolated_context:
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self.push()
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try:
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yield
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finally:
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self.template = initial
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if isolated_context:
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self.pop()
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class RequestContext(Context):
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"""
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This subclass of template.Context automatically populates itself using
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the processors defined in the engine's configuration.
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Additional processors can be specified as a list of callables
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using the "processors" keyword argument.
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"""
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def __init__(self, request, dict_=None, processors=None, use_l10n=None, use_tz=None, autoescape=True):
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super().__init__(dict_, use_l10n=use_l10n, use_tz=use_tz, autoescape=autoescape)
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self.request = request
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self._processors = () if processors is None else tuple(processors)
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self._processors_index = len(self.dicts)
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# placeholder for context processors output
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self.update({})
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# empty dict for any new modifications
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# (so that context processors don't overwrite them)
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self.update({})
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@contextmanager
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def bind_template(self, template):
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if self.template is not None:
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raise RuntimeError("Context is already bound to a template")
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self.template = template
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# Set context processors according to the template engine's settings.
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processors = (template.engine.template_context_processors +
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self._processors)
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updates = {}
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for processor in processors:
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updates.update(processor(self.request))
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self.dicts[self._processors_index] = updates
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try:
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yield
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finally:
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self.template = None
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# Unset context processors.
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self.dicts[self._processors_index] = {}
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def new(self, values=None):
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new_context = super().new(values)
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# This is for backwards-compatibility: RequestContexts created via
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# Context.new don't include values from context processors.
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if hasattr(new_context, '_processors_index'):
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del new_context._processors_index
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return new_context
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def make_context(context, request=None, **kwargs):
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"""
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Create a suitable Context from a plain dict and optionally an HttpRequest.
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"""
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if context is not None and not isinstance(context, dict):
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raise TypeError('context must be a dict rather than %s.' % context.__class__.__name__)
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if request is None:
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context = Context(context, **kwargs)
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else:
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# The following pattern is required to ensure values from
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# context override those from template context processors.
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original_context = context
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context = RequestContext(request, **kwargs)
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if original_context:
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context.push(original_context)
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return context
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