"falsey" conditional {?.x} is not treating 0 as false

As per https://github.com/linkedin/dustjs/pull/127#issuecomment-9510588, heavily simplified

Using the tool with this for the template:

{?.key}
a
{:else}
b
{/.key}

And this for the JSON:

{"key": 0}

Output I’m getting:

a

Output I’m expecting to get:

b

Occurring the same in both of the following tools: http://akdubya.github.com/dustjs/ http://linkedin.github.com/dustjs/test/test.html

For reference, I have tested in Safari on OS X and Chrome on Windows.

The following “falsey” values give the correct response - b:

{}
{"key": null}
{"key": false}
{"key": ""}

The integer value 0 (in Javascript) is also considered as “falsey”, as per the following:

(0 == false) returns true

Whether intentional or not, I feel this is a bug because zero is a “falsey” value.

[vybs]

Chunk.prototype.exists = function(elem, context, bodies) { var body = bodies.block, skip = bodies[‘else’];

if (!dust.isEmpty(elem)) { if (body) return body(this, context); } else if (skip) { return skip(this, context); } return this; };

it is the isEmpty method.

dust.isEmpty = function(value) { if (dust.isArray(value) && !value.length) return true; if (value === 0) return false; return (!value);

[dominykas]

“numeric 0 evaluates to true” <-- I do not think this is intuitive. What makes this hurt even more is that there are no keywords for true/false that we could pass as parameters - meaning that the only universal falsy value (other than non-existence/undefined) is “” (empty string).