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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 |
| 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 |
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