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 from jinja2._compat import string_types 15 16 17 class TrackingCodeGenerator(CodeGenerator): 18 """We abuse the code generator for introspection.""" 19 20 def __init__(self, environment): 21 CodeGenerator.__init__(self, environment, '<introspection>', 22 '<introspection>') 23 self.undeclared_identifiers = set() 24 25 def write(self, x): 26 """Don't write.""" 27 28 def pull_locals(self, frame): 29 """Remember all undeclared identifiers.""" 30 self.undeclared_identifiers.update(frame.identifiers.undeclared) 31 32 33 def find_undeclared_variables(ast): 34 """Returns a set of all variables in the AST that will be looked up from 35 the context at runtime. Because at compile time it's not known which 36 variables will be used depending on the path the execution takes at 37 runtime, all variables are returned. 38 39 >>> from jinja2 import Environment, meta 40 >>> env = Environment() 41 >>> ast = env.parse('{% set foo = 42 %}{{ bar + foo }}') 42 >>> meta.find_undeclared_variables(ast) 43 set(['bar']) 44 45 .. admonition:: Implementation 46 47 Internally the code generator is used for finding undeclared variables. 48 This is good to know because the code generator might raise a 49 :exc:`TemplateAssertionError` during compilation and as a matter of 50 fact this function can currently raise that exception as well. 51 """ 52 codegen = TrackingCodeGenerator(ast.environment) 53 codegen.visit(ast) 54 return codegen.undeclared_identifiers 55 56 57 def find_referenced_templates(ast): 58 """Finds all the referenced templates from the AST. This will return an 59 iterator over all the hardcoded template extensions, inclusions and 60 imports. If dynamic inheritance or inclusion is used, `None` will be 61 yielded. 62 63 >>> from jinja2 import Environment, meta 64 >>> env = Environment() 65 >>> ast = env.parse('{% extends "layout.html" %}{% include helper %}') 66 >>> list(meta.find_referenced_templates(ast)) 67 ['layout.html', None] 68 69 This function is useful for dependency tracking. For example if you want 70 to rebuild parts of the website after a layout template has changed. 71 """ 72 for node in ast.find_all((nodes.Extends, nodes.FromImport, nodes.Import, 73 nodes.Include)): 74 if not isinstance(node.template, nodes.Const): 75 # a tuple with some non consts in there 76 if isinstance(node.template, (nodes.Tuple, nodes.List)): 77 for template_name in node.template.items: 78 # something const, only yield the strings and ignore 79 # non-string consts that really just make no sense 80 if isinstance(template_name, nodes.Const): 81 if isinstance(template_name.value, string_types): 82 yield template_name.value 83 # something dynamic in there 84 else: 85 yield None 86 # something dynamic we don't know about here 87 else: 88 yield None 89 continue 90 # constant is a basestring, direct template name 91 if isinstance(node.template.value, string_types): 92 yield node.template.value 93 # a tuple or list (latter *should* not happen) made of consts, 94 # yield the consts that are strings. We could warn here for 95 # non string values 96 elif isinstance(node, nodes.Include) and \ 97 isinstance(node.template.value, (tuple, list)): 98 for template_name in node.template.value: 99 if isinstance(template_name, string_types): 100 yield template_name 101 # something else we don't care about, we could warn here 102 else: 103 yield None 104
