Incorrectly removing third curly bracket

[moif]

Experiencing this in Prettier's usage of Glimmer as reported here:
prettier/prettier#14090 (comment)
Where they state it is an issue in Glimmer itself.

Trying to add triple curly braces to be able to escape html content, but the third brace is removed if it's inside an html element.

onlyIf is a custom helper I am using on my project that evaluates on argument one, and then conditionally outputs argument two for context.

Input:

<input
  name="is-active"
  type="checkbox"
  value="active"
  {{{onlyIf active 'checked="checked"'}}}
/>

Output:

<input
  name="is-active"
  type="checkbox"
  value="active"
  {{onlyIf active 'checked="checked"'}}
/>

Expected behavior:
Output:

<input
  name="is-active"
  type="checkbox"
  value="active"
  {{{onlyIf active 'checked="checked"'}}}
/>

[Sam Van Campenhout]

Does the code work before Prettier strips the extra braces?

Curlies in that position are considered modifiers not "Mustache statements" so I don't think it can do what you are trying to do.

Would something like this work for you? It should have the same result.

<input
  name="is-active"
  type="checkbox"
  value="active"
  checked={{active}}
/>

[moif]

@Windvis
Yes the code works before prettier strips the extra braces (and I am currently getting around this issue by using Handlebars.SafeString but I shouldn't have to do that.

Unfortunately the code you shared does not give me the same result. Instead it makes checked equal to either "true" or "false" and 'checked'="false" still causes an html checkbox to be checked, you need to not have the attribute present at all for it to be unchecked.

To be extra clear as well I am coding in vanilla handlebars, and not using glimmer directly for parsing. I am only using it as a byproduct of it being how prettier formats handlebars files.

[Sam Van Campenhout]

@AW0005 Ah, I see. I assumed you where trying this in an Ember / Glimmer VM project (in which case the code snippet would trigger a build error and the snippet I posted would work as expected).

The Handlebars implementation in Ember / Glimmer is not the same as Handlebars.js. Prettier only includes support for the Glimmer subset so you would need a Handelbars.js specific Prettier plugin, but I'm not sure if that exists already.

[moif]

@Windvis
Yea unfortunately it does not - prettier themselves lists glimmer as their official handlebars support. I'll go back to them with this and see if they might not be able to add some kind of option on top for this somehow.