Empty htmlSafe string is treated as truthy

[buschtoens]

The {{if}} (and {{unless}}, {{with}}) template helpers treat an empty htmlSafe string as truthy, while an empty string is treated as falsy and even an empty array is treated as falsy.

{{if ''             'true' 'false'}} => false
{{if (html-safe '') 'true' 'false'}} => true
{{if (array)        'true' 'false'}} => false

Ember Twiddle

Interestingly I do not understand why an empty array is treated as falsy, when looking at the code:

ember.js/packages/@ember/-internals/glimmer/lib/helpers/if-unless.ts

Lines 41 to 47 in 1bea9af

	compute() {
	let branch = this.cond.value() ? this.truthy : this.falsy;
	this.branchTag.inner.update(branch.tag);
	return branch.value();
	}

[rwjblue]

Empty arrays are a falsey value in Handlebars across the board ( see https://handlebarsjs.com/builtin_helpers.html for example).

I haven’t really thought much about the empty safe string scenario though. I’d have to check what Handlebars does there...

[buschtoens]

Empty arrays are a falsey value in Handlebars across the board

Sure! Sorry for not expressing myself clearly enough. 😊

I know that [] is treated as false in Handlebars. I just don't understand how the compute method treats [] as false, since the ternary in L42 would treat [] as true.

I brought it up because there where this exception is implemented, we could also implement the exception for empty htmlSafe strings.

[chancancode]

@buschtoens this.cond is wrapped to have the ember semantics (and return a JS boolean, not the raw value)

[chancancode]

I think this is probably a bug.

https://github.com/emberjs/ember.js/blob/master/packages/%40ember/-internals/glimmer/lib/utils/to-bool.ts

(not sure what's up with that indentation)

[pzuraq]

This does seem like a bug, htmlSafe should be treated as transparent wrapper to strings conceptually, and an empty htmlSafe string should be falsy

[chancancode]

If anyone is interested in working on a fix, I believe adding a case to the function I linked above should fix it.