vibe.d selectively include attribute into tag using diet template

[JG via Digitalmars-d-learn]

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.