#442 Is `typ` a str or list of strings?

[Nick Brown]

The following code based on the example:

yaml = YAML(typ=["rt", "string"])

results in the following mypy error:

Argument "typ" to "YAML" has incompatible type "List[str]"; expected "Optional[str]"

Looking at https://sourceforge.net/u/jspricke/ruamel-yaml/ci/default/tree/main.py#l55
It appears to be typed hinted as Optional[Text]

However at https://sourceforge.net/u/jspricke/ruamel-yaml/ci/default/tree/main.py#l66

self.typ = ['rt'] if typ is None else (typ if isinstance(typ, list) else [typ])

It's always initialised as a list of typ.

In most the code that operates on typ it uses in which can work on either a list or a string.

So assuming that support for either a single string containing the different types, or list of strings of the types is intended, then perhaps the type hint should be Optional[List[Text] | Text] ?

Or should the type hint just be Optional[List[Text]]?

[Anthon van der Neut]

It should be Optional[List[Text] | Text].
Although internally a list of strings is presumed, for convenience you can provide just a string argument that is converted to a list of strings.

[Nick Brown]

Thanks for confirming @anthon. I've updated the commit in my MR: https://sourceforge.net/p/ruamel-yaml/code/merge-requests/7/

[Anthon van der Neut]

Fixed in 0.17.23, I had to change typ to Optional[Union[List[Text], Text]] as the
Union Operator from PEP 604 was not introduced until Python 3.10.