annotate venv/lib/python2.7/site-packages/jinja2/meta.py @ 0:d67268158946 draft

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