# -*- 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) 2017 by the Jinja Team, see AUTHORS for more details. :license: BSD, see LICENSE for more details. """ from jinja2 import nodes from jinja2.compiler import CodeGenerator from jinja2._compat import string_types, iteritems class TrackingCodeGenerator(CodeGenerator): """We abuse the code generator for introspection.""" def __init__(self, environment): CodeGenerator.__init__(self, environment, '<introspection>', '<introspection>') self.undeclared_identifiers = set() def write(self, x): """Don't write.""" def enter_frame(self, frame): """Remember all undeclared identifiers.""" CodeGenerator.enter_frame(self, frame) for _, (action, param) in iteritems(frame.symbols.loads): if action == 'resolve': self.undeclared_identifiers.add(param) 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']) True .. 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 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 not isinstance(node.template, nodes.Const): # a tuple with some non consts in there if isinstance(node.template, (nodes.Tuple, nodes.List)): for template_name in node.template.items: # something const, only yield the strings and ignore # non-string consts that really just make no sense if isinstance(template_name, nodes.Const): if isinstance(template_name.value, string_types): yield template_name.value # something dynamic in there else: yield None # something dynamic we don't know about here else: yield None continue # constant is a basestring, direct template name if isinstance(node.template.value, string_types): yield node.template.value # a tuple or list (latter *should* not happen) made of consts, # yield the consts that are strings. We could warn here for # non string values elif isinstance(node, nodes.Include) and \ isinstance(node.template.value, (tuple, list)): for template_name in node.template.value: if isinstance(template_name, string_types): yield template_name # something else we don't care about, we could warn here else: yield None