venv/lib/python3.11/site-packages/jinja2/meta.py

   1 """Functions that expose information about templates that might be
   2 interesting for introspection.
   3 """
   4 import typing as t
   5
   6 from . import nodes
   7 from .compiler import CodeGenerator
   8 from .compiler import Frame
   9
  10 if t.TYPE_CHECKING:
  11     from .environment import Environment
  12
  13
  14 class TrackingCodeGenerator(CodeGenerator):
  15     """We abuse the code generator for introspection."""
  16
  17     def __init__(self, environment: "Environment") -> None:
  18         super().__init__(environment, "<introspection>", "<introspection>")
  19         self.undeclared_identifiers: t.Set[str] = set()
  20
  21     def write(self, x: str) -> None:
  22         """Don't write."""
  23
  24     def enter_frame(self, frame: Frame) -> None:
  25         """Remember all undeclared identifiers."""
  26         super().enter_frame(frame)
  27
  28         for _, (action, param) in frame.symbols.loads.items():
  29             if action == "resolve" and param not in self.environment.globals:
  30                 self.undeclared_identifiers.add(param)
  31
  32
  33 def find_undeclared_variables(ast: nodes.Template) -> t.Set[str]:
  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) == {'bar'}
  43     True
  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)  # type: ignore
  53     codegen.visit(ast)
  54     return codegen.undeclared_identifiers
  55
  56
  57 _ref_types = (nodes.Extends, nodes.FromImport, nodes.Import, nodes.Include)
  58 _RefType = t.Union[nodes.Extends, nodes.FromImport, nodes.Import, nodes.Include]
  59
  60
  61 def find_referenced_templates(ast: nodes.Template) -> t.Iterator[t.Optional[str]]:
  62     """Finds all the referenced templates from the AST.  This will return an
  63     iterator over all the hardcoded template extensions, inclusions and
  64     imports.  If dynamic inheritance or inclusion is used, `None` will be
  65     yielded.
  66
  67     >>> from jinja2 import Environment, meta
  68     >>> env = Environment()
  69     >>> ast = env.parse('{% extends "layout.html" %}{% include helper %}')
  70     >>> list(meta.find_referenced_templates(ast))
  71     ['layout.html', None]
  72
  73     This function is useful for dependency tracking.  For example if you want
  74     to rebuild parts of the website after a layout template has changed.
  75     """
  76     template_name: t.Any
  77
  78     for node in ast.find_all(_ref_types):
  79         template: nodes.Expr = node.template  # type: ignore
  80
  81         if not isinstance(template, nodes.Const):
  82             # a tuple with some non consts in there
  83             if isinstance(template, (nodes.Tuple, nodes.List)):
  84                 for template_name in template.items:
  85                     # something const, only yield the strings and ignore
  86                     # non-string consts that really just make no sense
  87                     if isinstance(template_name, nodes.Const):
  88                         if isinstance(template_name.value, str):
  89                             yield template_name.value
  90                     # something dynamic in there
  91                     else:
  92                         yield None
  93             # something dynamic we don't know about here
  94             else:
  95                 yield None
  96             continue
  97         # constant is a basestring, direct template name
  98         if isinstance(template.value, str):
  99             yield template.value
 100         # a tuple or list (latter *should* not happen) made of consts,
 101         # yield the consts that are strings.  We could warn here for
 102         # non string values
 103         elif isinstance(node, nodes.Include) and isinstance(
 104             template.value, (tuple, list)
 105         ):
 106             for template_name in template.value:
 107                 if isinstance(template_name, str):
 108                     yield template_name
 109         # something else we don't care about, we could warn here
 110         else:
 111             yield None