Coverage for /pythoncovmergedfiles/medio/medio/usr/local/lib/python3.8/site-packages/jinja2/visitor.py: 23%

1"""API for traversing the AST nodes. Implemented by the compiler and 

2meta introspection. 

3""" 

4 

5import typing as t 

6 

7from .nodes import Node 

8 

9if t.TYPE_CHECKING: 

10 import typing_extensions as te 

11 

12 class VisitCallable(te.Protocol): 

13 def __call__(self, node: Node, *args: t.Any, **kwargs: t.Any) -> t.Any: ... 

14 

15 

16class NodeVisitor: 

17 """Walks the abstract syntax tree and call visitor functions for every 

18 node found. The visitor functions may return values which will be 

19 forwarded by the `visit` method. 

20 

21 Per default the visitor functions for the nodes are ``'visit_'`` + 

22 class name of the node. So a `TryFinally` node visit function would 

23 be `visit_TryFinally`. This behavior can be changed by overriding 

24 the `get_visitor` function. If no visitor function exists for a node 

25 (return value `None`) the `generic_visit` visitor is used instead. 

26 """ 

27 

28 def get_visitor(self, node: Node) -> "t.Optional[VisitCallable]": 

29 """Return the visitor function for this node or `None` if no visitor 

30 exists for this node. In that case the generic visit function is 

31 used instead. 

32 """ 

33 return getattr(self, f"visit_{type(node).__name__}", None) 

34 

35 def visit(self, node: Node, *args: t.Any, **kwargs: t.Any) -> t.Any: 

36 """Visit a node.""" 

37 f = self.get_visitor(node) 

38 

39 if f is not None: 

40 return f(node, *args, **kwargs) 

41 

42 return self.generic_visit(node, *args, **kwargs) 

43 

44 def generic_visit(self, node: Node, *args: t.Any, **kwargs: t.Any) -> t.Any: 

45 """Called if no explicit visitor function exists for a node.""" 

46 for child_node in node.iter_child_nodes(): 

47 self.visit(child_node, *args, **kwargs) 

48 

49 

50class NodeTransformer(NodeVisitor): 

51 """Walks the abstract syntax tree and allows modifications of nodes. 

52 

53 The `NodeTransformer` will walk the AST and use the return value of the 

54 visitor functions to replace or remove the old node. If the return 

55 value of the visitor function is `None` the node will be removed 

56 from the previous location otherwise it's replaced with the return 

57 value. The return value may be the original node in which case no 

58 replacement takes place. 

59 """ 

60 

61 def generic_visit(self, node: Node, *args: t.Any, **kwargs: t.Any) -> Node: 

62 for field, old_value in node.iter_fields(): 

63 if isinstance(old_value, list): 

64 new_values = [] 

65 for value in old_value: 

66 if isinstance(value, Node): 

67 value = self.visit(value, *args, **kwargs) 

68 if value is None: 

69 continue 

70 elif not isinstance(value, Node): 

71 new_values.extend(value) 

72 continue 

73 new_values.append(value) 

74 old_value[:] = new_values 

75 elif isinstance(old_value, Node): 

76 new_node = self.visit(old_value, *args, **kwargs) 

77 if new_node is None: 

78 delattr(node, field) 

79 else: 

80 setattr(node, field, new_node) 

81 return node 

82 

83 def visit_list(self, node: Node, *args: t.Any, **kwargs: t.Any) -> t.List[Node]: 

84 """As transformers may return lists in some places this method 

85 can be used to enforce a list as return value. 

86 """ 

87 rv = self.visit(node, *args, **kwargs) 

88 

89 if not isinstance(rv, list): 

90 return [rv] 

91 

92 return rv