1 # -*- coding: utf-8 -*- 2 """ 3 jinja2.meta 4 ~~~~~~~~~~~ 5 6 This module implements various functions that exposes information about 7 templates that might be interesting for various kinds of applications. 8 9 :copyright: (c) 2010 by the Jinja Team, see AUTHORS for more details. 10 :license: BSD, see LICENSE for more details. 11 """ 12 from jinja2 import nodes 13 from jinja2.compiler import CodeGenerator 14 15 16 class TrackingCodeGenerator(CodeGenerator): 17 """We abuse the code generator for introspection.""" 18 19 def __init__(self, environment): 20 CodeGenerator.__init__(self, environment, '<introspection>', 21 '<introspection>') 22 self.undeclared_identifiers = set() 23 24 def write(self, x): 25 """Don't write.""" 26 27 def pull_locals(self, frame): 28 """Remember all undeclared identifiers.""" 29 self.undeclared_identifiers.update(frame.identifiers.undeclared) 30 31 32 def find_undeclared_variables(ast): 33 """Returns a set of all variables in the AST that will be looked up from 34 the context at runtime. Because at compile time it's not known which 35 variables will be used depending on the path the execution takes at 36 runtime, all variables are returned. 37 38 >>> from jinja2 import Environment, meta 39 >>> env = Environment() 40 >>> ast = env.parse('{% set foo = 42 %}{{ bar + foo }}') 41 >>> meta.find_undeclared_variables(ast) 42 set(['bar']) 43 44 .. admonition:: Implementation 45 46 Internally the code generator is used for finding undeclared variables. 47 This is good to know because the code generator might raise a 48 :exc:`TemplateAssertionError` during compilation and as a matter of 49 fact this function can currently raise that exception as well. 50 """ 51 codegen = TrackingCodeGenerator(ast.environment) 52 codegen.visit(ast) 53 return codegen.undeclared_identifiers 54 55 56 def find_referenced_templates(ast): 57 """Finds all the referenced templates from the AST. This will return an 58 iterator over all the hardcoded template extensions, inclusions and 59 imports. If dynamic inheritance or inclusion is used, `None` will be 60 yielded. 61 62 >>> from jinja2 import Environment, meta 63 >>> env = Environment() 64 >>> ast = env.parse('{% extends "layout.html" %}{% include helper %}') 65 >>> list(meta.find_referenced_templates(ast)) 66 ['layout.html', None] 67 68 This function is useful for dependency tracking. For example if you want 69 to rebuild parts of the website after a layout template has changed. 70 """ 71 for node in ast.find_all((nodes.Extends, nodes.FromImport, nodes.Import, 72 nodes.Include)): 73 if not isinstance(node.template, nodes.Const): 74 # a tuple with some non consts in there 75 if isinstance(node.template, (nodes.Tuple, nodes.List)): 76 for template_name in node.template.items: 77 # something const, only yield the strings and ignore 78 # non-string consts that really just make no sense 79 if isinstance(template_name, nodes.Const): 80 if isinstance(template_name.value, basestring): 81 yield template_name.value 82 # something dynamic in there 83 else: 84 yield None 85 # something dynamic we don't know about here 86 else: 87 yield None 88 continue 89 # constant is a basestring, direct template name 90 if isinstance(node.template.value, basestring): 91 yield node.template.value 92 # a tuple or list (latter *should* not happen) made of consts, 93 # yield the consts that are strings. We could warn here for 94 # non string values 95 elif isinstance(node, nodes.Include) and \ 96 isinstance(node.template.value, (tuple, list)): 97 for template_name in node.template.value: 98 if isinstance(template_name, basestring): 99 yield template_name 100 # something else we don't care about, we could warn here 101 else: 102 yield None 103
