vibe.d selectively include attribute into tag using diet template

[JG]

Hi,

I know that one can do the following:
tag(attribute='#{dexpression}')

But, is there a way to deal with attributes that don't get 
assigned values.
That is, is there a way to produce
<tag>
or
<tag attribute>
depending on a boolean variable?

Of course one can do:
- if (booleanVariable)
  tag(attribute)
   include ...
- if (!booleanVariable)
  tag
   include ...

But this seems rather messy.