We need to talk about IFormattable.ToString()

[chrisimcevoy]

#152 added a TODO because python's __format__ allows us to specify a format_spec (which in the context of Pyoda Time constitutes a "pattern", standard or otherwise).

What it doesn't allow us to do is specify a CultureInfo, naturally.

Maybe we should implement a def to_string(self, pattern, format_provider) equivalent to IFormattable.ToString()?

[chrisimcevoy]

That said, this needs to fit into a wider discussion around CultureInfo usage and what exactly we want to expose publicly...

[chrisimcevoy]

There are some types like Duration where the tests don't seem to explicitly cover IFormattable.ToString(), or even object.ToString(), explicitly.

I suspect the coverage comes from this section of code in Noda Time.

It's currently a TODO in Pyoda Time, so we'll wanna implement that too if an IFormattable protocol materialises in the codebase.