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107 lines
4.2 KiB
107 lines
4.2 KiB
8 years ago
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# -*- coding: utf-8 -*-
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"""
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jinja2.meta
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~~~~~~~~~~~
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This module implements various functions that exposes information about
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templates that might be interesting for various kinds of applications.
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:copyright: (c) 2017 by the Jinja Team, see AUTHORS for more details.
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:license: BSD, see LICENSE for more details.
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"""
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from jinja2 import nodes
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from jinja2.compiler import CodeGenerator
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from jinja2._compat import string_types, iteritems
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class TrackingCodeGenerator(CodeGenerator):
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"""We abuse the code generator for introspection."""
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def __init__(self, environment):
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CodeGenerator.__init__(self, environment, '<introspection>',
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'<introspection>')
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self.undeclared_identifiers = set()
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def write(self, x):
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"""Don't write."""
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def enter_frame(self, frame):
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"""Remember all undeclared identifiers."""
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CodeGenerator.enter_frame(self, frame)
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for _, (action, param) in iteritems(frame.symbols.loads):
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if action == 'resolve':
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self.undeclared_identifiers.add(param)
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def find_undeclared_variables(ast):
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"""Returns a set of all variables in the AST that will be looked up from
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the context at runtime. Because at compile time it's not known which
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variables will be used depending on the path the execution takes at
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runtime, all variables are returned.
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>>> from jinja2 import Environment, meta
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>>> env = Environment()
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>>> ast = env.parse('{% set foo = 42 %}{{ bar + foo }}')
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>>> meta.find_undeclared_variables(ast) == set(['bar'])
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True
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.. admonition:: Implementation
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Internally the code generator is used for finding undeclared variables.
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This is good to know because the code generator might raise a
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:exc:`TemplateAssertionError` during compilation and as a matter of
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fact this function can currently raise that exception as well.
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"""
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codegen = TrackingCodeGenerator(ast.environment)
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codegen.visit(ast)
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return codegen.undeclared_identifiers
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def find_referenced_templates(ast):
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"""Finds all the referenced templates from the AST. This will return an
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iterator over all the hardcoded template extensions, inclusions and
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imports. If dynamic inheritance or inclusion is used, `None` will be
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yielded.
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>>> from jinja2 import Environment, meta
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>>> env = Environment()
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>>> ast = env.parse('{% extends "layout.html" %}{% include helper %}')
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>>> list(meta.find_referenced_templates(ast))
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['layout.html', None]
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This function is useful for dependency tracking. For example if you want
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to rebuild parts of the website after a layout template has changed.
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"""
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for node in ast.find_all((nodes.Extends, nodes.FromImport, nodes.Import,
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nodes.Include)):
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if not isinstance(node.template, nodes.Const):
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# a tuple with some non consts in there
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if isinstance(node.template, (nodes.Tuple, nodes.List)):
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for template_name in node.template.items:
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# something const, only yield the strings and ignore
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# non-string consts that really just make no sense
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if isinstance(template_name, nodes.Const):
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if isinstance(template_name.value, string_types):
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yield template_name.value
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# something dynamic in there
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else:
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yield None
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# something dynamic we don't know about here
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else:
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yield None
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continue
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# constant is a basestring, direct template name
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if isinstance(node.template.value, string_types):
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yield node.template.value
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# a tuple or list (latter *should* not happen) made of consts,
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# yield the consts that are strings. We could warn here for
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# non string values
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elif isinstance(node, nodes.Include) and \
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isinstance(node.template.value, (tuple, list)):
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for template_name in node.template.value:
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if isinstance(template_name, string_types):
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yield template_name
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# something else we don't care about, we could warn here
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else:
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yield None
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