Support boolean conditionals

[anowell]

It'd be nice to be able to express at least basic boolean conditionals in templates.

{{#is_condition}}content{{/is_condition}

This actually works if if is_condition is an Option<()> (thanks to IntoIterator), but not if it is a bool.

[maghoff]

Yeah, I'm exploring a design for this. It is not documented, but it is actually possible already, by using a trailing ?, like so:

{{#is_condition?}}content{{/is_condition}}

Limiting it to bool seems weird, so I have introduced a Conditional trait in between there, which you can make use of to have other types as the condition.

You might want to look at the relevant tests.

Thanks for your feedback, keep it coming :) I am going to close this now, but feel free to give feedback about how you feel this is working and where you might find it lacking.

[anowell]

Perfect. Thanks.