empty safehtml.HTML is true, should be false

[jba]

There is an incompatibility with html/template. The empty escaped template value template.HTML("") is false an in if, just as the empty string is. But the zero value safehtml.HTML{} is true.

See https://play.golang.org/p/iKB2uBICUX-.

[jba]

I have a PR to fix template.IsTrue, but unfortunately I think fixing template execution is harder. The text/template execution engine is used, and it seems to have its version of IsTrue hardcoded.

Probably best not to "fix" template.IsTrue if execution doesn't match it.

[jba]

Maybe the best thing to do is to document clearly that if .X was previously a string or template.HTML and is now a safehtml.HTML or other safehtml type, one must replace

{{if .X}}

with

{{if .X.String}}

[5psf]

Thanks for flagging this, we'll take a look at possible solutions, although at the moment updating the documentation seems the most probable outcome. safehtml/template tries to be as close to a drop-in replacement as possible, but the migration will never be 100% transparent, and this could be another of those divergences.

Probably best not to "fix" template.IsTrue if execution doesn't match it.

+1 for having a uniform behavior.