Return Iterator when possible

[wiiznokes]

• change Option<Vec> signatures to impl Iterator<Item = &'a str>
• use split_terminator instead of split

Equivalent to [split], except that the trailing substring is skipped if empty.

[leb-kuchen]

I am not sure about the removal of option.

[wiiznokes]

This is kinda necessary if we want to return an opaque Iterator, because before we used

let b = entry.mime_type().unwrap_or_default().iter().any(|m|m == "f");

And with an option:

entry.mime_type().map(|i| i.any(|m|m == "f")).unwrap_or(false);

instead of

let b = entry.mime_type().any(|m|m == "f");

I don't really see an use case to handle the case where the field is not defined, but if someone want to handle it, he could use his own functions.

[leb-kuchen]

I don't think .unwrap_or_else(|| "".split_terminator(';')) or into_iter().flatten() is difficult to write.
If it is intuitive and there are not any use cases, it may be still be worth to remove the Option,

I think SplitTerminator should be returned instead of an opaque type. This way .into_remainder() can be used to get the actual string.

[wiiznokes]

I think SplitTerminator should be returned instead of an opaque type. This way rust-lang/rust#77998 can be used to get the actual string

Yeah good idea