false values turn into nil

[kanwei]

Passing in something as a boolean false seems to turn into a nil. So:

(println (render "Blah {{boo|str}}" {:boo false}))

prints "Blah" instead of "Blah false" as expected when doing (str false) in regular clojure.

[yogthos]

That's because lookup in the context map that results in a false is treated as absence of value, so it never gets to the filter. Changing this would affect the existing API however, so I'd be hesitant to do that. A workaround would be to stringify false values before passing them to render.

[brunchboy]

Whoops, it looks like this tripped us up in our API documentation generator, which relies on some nested Selmer templates and custom tags, as well. I think your suggested workaround may work for us, though, because I am tracking separately whether the value being rendered is supposed to be a string literal or not.

[pimeys]

Is this going to be fixed at some point? We just found the bug on production and were kind of surprised how it works. (str value) of course helps for now.

[yogthos]

My only hesitation here is that it would be a breaking API change for the library. Perhaps one approach would be to make this a configuration option.

[mlococo]

Personally, I'd rev the major version at some point and fix this. I get that breaking changes are a big deal, but I have trouble believing that anyone wants this behavior. It seems like leaving a landmine for new users in perpetuity is the greater evil compared to a breaking change properly labelled in a major release.

This bit me in a real-world project and caused, what was from my perspective, a rendering bug in the resulting application that was present for several releases before being found by internal testing and only then did we find this bug report.

[yogthos]

It sounds like the consensus here is that it would be a desirable change. I'm open to a PR for this. The breaking change could be noted in the change log. I think that would be adequate.