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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 | |
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