TypeError: 'NoneType' object is not iterable

[mgedmin]

I noticed that my vim stopped highlighting YAML syntax errors. I ran yamllint directly on a file I was editing and saw

Traceback (most recent call last):
  File "/home/mg/.local/bin/yamllint", line 8, in <module>
    sys.exit(run())
  File "/home/mg/.local/pipx/venvs/yamllint/lib/python3.8/site-packages/yamllint/cli.py", line 168, in run
    conf = YamlLintConfig(file=user_global_config)
  File "/home/mg/.local/pipx/venvs/yamllint/lib/python3.8/site-packages/yamllint/config.py", line 42, in __init__
    self.parse(content)
  File "/home/mg/.local/pipx/venvs/yamllint/lib/python3.8/site-packages/yamllint/config.py", line 83, in parse
    for rule in self.rules:
TypeError: 'NoneType' object is not iterable

Turns out this was caused by my ~/.config/yamllint/config containing

extends: relaxed
rules:
line-length:
  max: 200

I'm pretty sure this used to work before I did some pip upgrades.

I fixed my problem by changing the config to explicitly set rules: [], but I wonder if you'd want to catch this kind of type error in the YAML config and produce better error messages? Or even allow null values and treat them as empty lists/dicts?

[adrienverge]

Hi Marius,

I'm glad you managed to get it to work again 👍

If using an empty rules: once worked, it was a hidden feature that was never meant to exist. For clarity and consistency, I think it's better to stick to what rules is (a dict). I agree a more friendly error message would be better.

[mgedmin]

Oh, it's a dict! I'll go and fix my config again, before stricter typechecking breaks my editor plugins, again :)

[adrienverge]

Hehe. You can see an example of a full configuration here: https://yamllint.readthedocs.io/en/stable/configuration.html#default-configuration