TypeError in indentation rule when parsing invalid YAML file

[scharfy]

When running yamllint (v1.37.1) on Python 3.11, I encountered a TypeError in the indentation rule when processing a specific YAML file used in my unit tests.
The file is intentionally invalid YAML (garbage content).

workflow-invalid.yml

THI IS:
}¬} invlid"
    >YAML

Unfortunately, I have not been able to create a minimal reproducible example from scratch — the crash only happens with this particular file in my project.

When I add this file to the ignore section in .yamllint, the error disappears and yamllint runs normally again.

Traceback (most recent call last):
  File "/home/user/.local/bin/yamllint", line 8, in <module>
    sys.exit(run())
  File "/home/user/.local/lib/python3.11/site-packages/yamllint/cli.py", line 227, in run
    prob_level = show_problems(problems, file, args_format=args.format,
  File "/home/user/.local/lib/python3.11/site-packages/yamllint/cli.py", line 102, in show_problems
    for problem in problems:
  File "/home/user/.local/lib/python3.11/site-packages/yamllint/linter.py", line 201, in _run
    for problem in get_cosmetic_problems(buffer, conf, filepath):
  File "/home/user/.local/lib/python3.11/site-packages/yamllint/linter.py", line 136, in get_cosmetic_problems
    for problem in rule.check(rule_conf,
  File "/home/user/.local/lib/python3.11/site-packages/yamllint/rules/indentation.py", line 582, in check
    yield from _check(conf, token, prev, next, nextnext, context)
  File "/home/user/.local/lib/python3.11/site-packages/yamllint/rules/indentation.py", line 343, in _check
    if expected < 0:
TypeError: '<' not supported between instances of 'NoneType' and 'int'

Expected behavior:
Invalid YAML should result in a parsing error message, not a crash.

Workaround:
Adding the file to .yamllint’s ignore list resolves the problem.

Environment:

yamllint: 1.37.1

Python: 3.11

OS: Ubuntu 24.04.3 LTS

Maybe just make sure expected is never NoneType?

Greetings from austria

[adrienverge]

Hello @scharfy,

Unfortunately, I have not been able to create a minimal reproducible example from scratch — the crash only happens with this particular file in my project.

You need to share a minimal reproducer, otherwise we can't debug the probem.

For info I'm not able to reproduce any bug with your example snippet:

THI IS:
}¬} invlid"
    >YAML