Escaping overlay vars (mustache variables) inside template files

[posilva]

Hi

How to use bbmustache to allow to scape mustache variables, what I want is:

• I have a file (my_template_sys.config.tpl) that has overlay vars, for example, we always use a config like: {environment, {{environment_var}}}.
• When I run rebar3 new my_template myservice the environment config in sys.config is generated {environment, } because in the rebar3 template generation the variable is expanded and because does not exists in the context of the rebar3 template it will be replaced by “nothing”

Any sugestion?

Thank you

Pedro

[soranoba]

Discussion was done on slack.
https://erlanger.slack.com/archives/C055DJA49/p1493986463810192

[posilva]

Fixed using set delimiter: http://mustache.github.io/mustache.5.html

The trick is when we want to “escape” a variable we can change the delimiter right before, and after the variable declaration we change back to the default delimiter.

 { {{ name }}, [
        %% Application settings
        {environment, {{=<% %>=}}{{environment}}<%={{ }}=%>},
        {major, "{{=<% %>=}}{{major}}<%={{ }}=%>"},

        %% Network Settings
        {cluster_node_discover, {{=<% %>=}}{{cluster_node_discover}}<%={{ }}=%>},
        {server_interface, {{=<% %>=}}{{server_interface}}<%={{ }}=%> },
        { {{custom_parameter}}, param_value }
    ]}

With {{=<% %>=}} we change the delimiter as <% %>, then we declare the "escaped variable " {{cluster_node_discover}} and after that we set the default delimiter with <%={{ }}=%>

The template variable {{custom_parameter}} is not escaped and because the previous variables have the default delimiter set, this variable will be processed correctly by template engine.

I hope this helps