Fix an infinite recursion error.

[yilei]

Description

This bug appears to have existed earlier. But it's now triggered on the added test after #3440 on the complex dict value.

The infinite recursion happens when getting the second_opinion. Example traceback:

Traceback (most recent call last):
  File "/Users/yileiyang/github.com/yilei/black/src/black/__init__.py", line 1077, in format_str
    dst_contents = _format_str_once(src_contents, mode=mode)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/yileiyang/github.com/yilei/black/src/black/__init__.py", line 1109, in _format_str_once
    for line in transform_line(
  File "/Users/yileiyang/github.com/yilei/black/src/black/linegen.py", line 577, in transform_line
    result = run_transformer(line, transform, mode, features, line_str=line_str)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/yileiyang/github.com/yilei/black/src/black/linegen.py", line 1418, in run_transformer
    result.extend(transform_line(transformed_line, mode=mode, features=features))
  File "/Users/yileiyang/github.com/yilei/black/src/black/linegen.py", line 577, in transform_line
    result = run_transformer(line, transform, mode, features, line_str=line_str)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/yileiyang/github.com/yilei/black/src/black/linegen.py", line 1418, in run_transformer
    result.extend(transform_line(transformed_line, mode=mode, features=features))
  File "/Users/yileiyang/github.com/yilei/black/src/black/linegen.py", line 577, in transform_line
    result = run_transformer(line, transform, mode, features, line_str=line_str)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/yileiyang/github.com/yilei/black/src/black/linegen.py", line 1418, in run_transformer
    result.extend(transform_line(transformed_line, mode=mode, features=features))
  File "/Users/yileiyang/github.com/yilei/black/src/black/linegen.py", line 577, in transform_line
    result = run_transformer(line, transform, mode, features, line_str=line_str)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/yileiyang/github.com/yilei/black/src/black/linegen.py", line 1418, in run_transformer
    result.extend(transform_line(transformed_line, mode=mode, features=features))
  File "/Users/yileiyang/github.com/yilei/black/src/black/linegen.py", line 577, in transform_line
    result = run_transformer(line, transform, mode, features, line_str=line_str)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/yileiyang/github.com/yilei/black/src/black/linegen.py", line 1418, in run_transformer
    result.extend(transform_line(transformed_line, mode=mode, features=features))
  File "/Users/yileiyang/github.com/yilei/black/src/black/linegen.py", line 577, in transform_line
    result = run_transformer(line, transform, mode, features, line_str=line_str)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/yileiyang/github.com/yilei/black/src/black/linegen.py", line 1418, in run_transformer
    result.extend(transform_line(transformed_line, mode=mode, features=features))
  File "/Users/yileiyang/github.com/yilei/black/src/black/linegen.py", line 577, in transform_line
    result = run_transformer(line, transform, mode, features, line_str=line_str)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/yileiyang/github.com/yilei/black/src/black/linegen.py", line 1442, in run_transformer
    second_opinion = run_transformer(
                     ^^^^^^^^^^^^^^^^
  File "/Users/yileiyang/github.com/yilei/black/src/black/linegen.py", line 1442, in run_transformer
    second_opinion = run_transformer(
                     ^^^^^^^^^^^^^^^^
  File "/Users/yileiyang/github.com/yilei/black/src/black/linegen.py", line 1442, in run_transformer
    second_opinion = run_transformer(
                     ^^^^^^^^^^^^^^^^
  [Previous line repeated 950 more times]
  File "/Users/yileiyang/github.com/yilei/black/src/black/linegen.py", line 1418, in run_transformer
    result.extend(transform_line(transformed_line, mode=mode, features=features))
  File "/Users/yileiyang/github.com/yilei/black/src/black/linegen.py", line 577, in transform_line
    result = run_transformer(line, transform, mode, features, line_str=line_str)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/yileiyang/github.com/yilei/black/src/black/linegen.py", line 1418, in run_transformer
    result.extend(transform_line(transformed_line, mode=mode, features=features))
  File "/Users/yileiyang/github.com/yilei/black/src/black/linegen.py", line 577, in transform_line
    result = run_transformer(line, transform, mode, features, line_str=line_str)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/yileiyang/github.com/yilei/black/src/black/linegen.py", line 1414, in run_transformer
    for transformed_line in transform(line, features):
  File "/Users/yileiyang/github.com/yilei/black/src/black/trans.py", line 240, in __call__
    match_result = self.do_match(line)
                   ^^^^^^^^^^^^^^^^^^^
  File "/Users/yileiyang/github.com/yilei/black/src/black/trans.py", line 883, in do_match
    match_result = self.do_splitter_match(line)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/yileiyang/github.com/yilei/black/src/black/trans.py", line 1207, in do_splitter_match
    idx = string_parser.parse(LL, string_idx)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/yileiyang/github.com/yilei/black/src/black/trans.py", line 2088, in parse
    while idx < len(leaves) and self._next_state(leaves[idx]):
                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/yileiyang/github.com/yilei/black/src/black/trans.py", line 2106, in _next_state
    if is_empty_par(leaf):
       ^^^^^^^^^^^^^^^^^^
  File "/Users/yileiyang/github.com/yilei/black/src/black/nodes.py", line 756, in is_empty_par
    return is_empty_lpar(leaf) or is_empty_rpar(leaf)
           ^^^^^^^^^^^^^^^^^^^
  File "/Users/yileiyang/github.com/yilei/black/src/black/nodes.py", line 760, in is_empty_lpar
    return leaf.type == token.LPAR and leaf.value == ""
           ^^^^^^^^^^^^^^^^^^^^^^^
RecursionError: maximum recursion depth exceeded in comparison

Checklist - did you ...

• Add an entry in CHANGES.md if necessary?
• Add / update tests if necessary?
• Add new / update outdated documentation?

[github-actions]

diff-shades reports zero changes comparing this PR (6627322) to main (aafc21a).

---

What is this? | Workflow run | diff-shades documentation

[JelleZijlstra]

Thanks for noticing and fixing!