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# -*- coding: utf-8 -*- | ||
""" | ||
jinja2.meta | ||
~~~~~~~~~~~ | ||
This module implements various functions that exposes information about | ||
templates that might be interesting for various kinds of applications. | ||
:copyright: (c) 2009 by the Jinja2 Team, see AUTHORS for more details. | ||
:license: BSD, see LICENSE for more details. | ||
""" | ||
from jinja2 import nodes | ||
from jinja2.compiler import CodeGenerator | ||
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class TrackingCodeGenerator(CodeGenerator): | ||
"""We abuse the code generator for introspection.""" | ||
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def __init__(self, environment): | ||
CodeGenerator.__init__(self, environment, '<introspection>', | ||
'<introspection>') | ||
self.undeclared_identifiers = set() | ||
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def write(self, x): | ||
"""Don't write.""" | ||
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def pull_locals(self, frame): | ||
"""Remember all undeclared identifiers.""" | ||
self.undeclared_identifiers.update(frame.identifiers.undeclared) | ||
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def find_undeclared_variables(ast): | ||
"""Returns a set of all variables in the AST that will be looked up from | ||
the context at runtime. Because at compile time it's not known which | ||
variables will be used depending on the path the execution takes at | ||
runtime, all variables are returned. | ||
>>> from jinja2 import Environment, meta | ||
>>> env = Environment() | ||
>>> ast = env.parse('{% set foo = 42 %}{{ bar + foo }}') | ||
>>> meta.find_undeclared_variables(ast) | ||
set(['bar']) | ||
.. admonition:: Implementation | ||
Internally the code generator is used for finding undeclared variables. | ||
This is good to know because the code generator might raise a | ||
:exc:`TemplateAssertionError` during compilation and as a matter of | ||
fact this function can currently raise that exception as well. | ||
""" | ||
codegen = TrackingCodeGenerator(ast.environment) | ||
codegen.visit(ast) | ||
return codegen.undeclared_identifiers | ||
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def find_referenced_templates(ast): | ||
"""Finds all the referenced templates from the AST. This will return an | ||
iterator over all the hardcoded template extensions, inclusions and | ||
imports. If dynamic inheritance or inclusion is used, `None` will be | ||
yielded. | ||
>>> from jinja2 import Environment, meta | ||
>>> env = Environment() | ||
>>> ast = env.parse('{% extends "layout.html" %}{% include helper %}') | ||
>>> list(meta.find_referenced_templates(ast)) | ||
['layout.html', None] | ||
This function is useful for dependency tracking. For example if you want | ||
to rebuild parts of the website after a layout template has changed. | ||
""" | ||
for node in ast.find_all((nodes.Extends, nodes.FromImport, nodes.Import, | ||
nodes.Include)): | ||
if isinstance(node.template, nodes.Const) and \ | ||
isinstance(node.template.value, basestring): | ||
yield node.template.value | ||
else: | ||
yield None |