deprecate and remove if helper

[jimmyhchan]

We have strongly discouraged the use of the if helper. Can we formally deprecate and remove it?

[rragan]

Is the deprecation because it uses eval or because it encourages logic in templates? This will break lots of folks (sadly). Maybe we can create a dustjs-helper-deprecated file and folks who want to use it would have to pull that one in as well.

There is my alternative which does not use eval and limits the scope of expressions allowed for people who need it. https://github.com/rragan/dust-motes/tree/master/src/helpers/control/if

[smfoote]

I would say the primary motivation for removing @if is because it uses eval, but I think the additional logic it allows in templates is also a step in the wrong direction for a "logicless" template language.

I say we deprecate and remove it. This is versioned software, so if the new version breaks someone's templates, they can just keep using the old version.

[jimmyhchan]

I don't intend for this to happen suddenly. This will cause some pain for folks. Hopefully this issue will conclude with

• timeline for removal
• recommendation for those who still need the deprecated functionality

We definitely want a way for folks to opt into using the deprecated helper, but it should not be the default. Would love some thought around the options (separate repo, separate branch, a flag somehow...)

[sethkinast]

A good first step would be to start throwing a warn when the helper is
invoked.