src/black/debug.py

   1 from dataclasses import dataclass
   2 from typing import Iterator, TypeVar, Union
   3
   4 from blib2to3.pytree import Node, Leaf, type_repr
   5 from blib2to3.pgen2 import token
   6
   7 from black.nodes import Visitor
   8 from black.output import out
   9 from black.parsing import lib2to3_parse
  10
  11 LN = Union[Leaf, Node]
  12 T = TypeVar("T")
  13
  14
  15 @dataclass
  16 class DebugVisitor(Visitor[T]):
  17     tree_depth: int = 0
  18
  19     def visit_default(self, node: LN) -> Iterator[T]:
  20         indent = " " * (2 * self.tree_depth)
  21         if isinstance(node, Node):
  22             _type = type_repr(node.type)
  23             out(f"{indent}{_type}", fg="yellow")
  24             self.tree_depth += 1
  25             for child in node.children:
  26                 yield from self.visit(child)
  27
  28             self.tree_depth -= 1
  29             out(f"{indent}/{_type}", fg="yellow", bold=False)
  30         else:
  31             _type = token.tok_name.get(node.type, str(node.type))
  32             out(f"{indent}{_type}", fg="blue", nl=False)
  33             if node.prefix:
  34                 # We don't have to handle prefixes for `Node` objects since
  35                 # that delegates to the first child anyway.
  36                 out(f" {node.prefix!r}", fg="green", bold=False, nl=False)
  37             out(f" {node.value!r}", fg="blue", bold=False)
  38
  39     @classmethod
  40     def show(cls, code: Union[str, Leaf, Node]) -> None:
  41         """Pretty-print the lib2to3 AST of a given string of `code`.
  42
  43         Convenience method for debugging.
  44         """
  45         v: DebugVisitor[None] = DebugVisitor()
  46         if isinstance(code, str):
  47             code = lib2to3_parse(code)
  48         list(v.visit(code))