Question

I was trying to render a mustache template which is referencing itself in it. But it gives a ‘Stack level too deep’ error.

Here is my code in ruby.

The following snippet of code is in person.rb file

require 'mustache'
require 'active_support'

str = File.read("person.json")
j = ActiveSupport::JSON.decode(str)
Mustache.template_file = "person.mustache"
puts Mustache.render(j)

The following json content is in person.json

{
    "name":"Jason",
    "rels":[
        {"type":"friend",
        "ref":{
            "name":"John",
            "rels":[
                {"type":"friend",
                "ref":{"name":"Chrissy"}}
            ]
        }},
        {"type":"family",
        "ref":{"name":"Owen"}}
    ]
}

The following content is in the file person.mustache file

{{#rels}}
<ul>
  <li>Type: {{type}}</li>
  {{#ref}} {{> person}} {{/ref}}
</ul>
{{/rels}}

can someone point me in the right direction?

Answer 1

From the fine manual:

Partials
[…]
They also inherit the calling context. Whereas in ERB you may have this:

<%= partial :next_more, :start => start, :size => size %>

Mustache requires only this:

{{> next_more}}

Why? Because the next_more.mustache file will inherit the size and start methods from the calling context.

So, if there is no rels in the current context:

    "ref": { "name": "Chrissy" }

then you’ll inherit the rels from the parent. That gives you a partial referencing rels from the parent which activates the partial again which references rels from the parent which keeps going until you run out of stack.

If you’re going to build a recursive template like this:

{{#rels}}
<ul>
  <li>Type: {{type}}</li>
  {{#ref}} {{> person}} {{/ref}}
</ul>
{{/rels}}

then you need to have complete objects at each level:

{
    "name":"Jason",
    "rels":[
        {"type":"friend",
        "ref":{
            "name":"John",
            "rels":[
                {"type":"friend",
                "ref":{"name":"Chrissy","rels":[]}} // <--- rels here
            ]
        }},
        {"type":"family",
        "ref":{"name":"Owen","rels":[]}} // <-------------- and here
    ]
}

You can flesh out your data in the JSON or after you parse it, I’d recommend that you flesh it out after parsing it.