Mustache rendering {{#current}} blocks break page context

[roblillack]

According to the Mustache spec, rendering a section by accessing a boolean value like current this should happen:

use a single-element list containing the data, otherwise use an empty list. For each element in the data list, the element MUST be pushed onto the context stack, the section MUST be rendered, and the element MUST be popped off the context stack.

—https://github.com/mustache/spec/blob/master/specs/sections.yml

This means, that a block like this:

{{#navigation}}
{{#current}}{{name}}{{/current}}
{{^current}}<a href="{{permalink}}">{{name}}</a>{{/current}}
{{/navigation}}

should render

<a href="/a">A</a>
B
<a href="/c">C</a>

for this context:

{
  "name": "B",
  "permalink": "/b",
  "navigation": [
    {
      "name": "A",
      "permalink": "/a"
    },
    {
      "current": true,
      "name": "B",
      "permalink": "/b"
    },
    {
      "name": "C",
      "permalink": "/c"
    }
  ]
}

But instead it renders:

<a href="/b">B</a>
B
<a href="/b">B</a>

as the variables inside the current will be resolved from the top level not the iterated navigation.

[roblillack]

This currently breaks many #navigation use-cases.

I opened a ticket upstream: cbroglie/mustache#53 – let's see.