How do I render a template from a (non-block) helper?

[heemskerkerik]

I'm trying to implement a front-end for Ghost, and one of the helpers they expose to their themes is {{navigation}}, which pulls a JSON object from settings, and feeds that to another template.

The basics are simple:

var vm = new
         {
             navigation = new[]
                          {
                              new
                              {
                                  label = "Home",
                                  url = "/",
                              }
                          }
         };

var view = handlebars.CompileView("navigation.hbs");
using var writer = output.CreateWrapper();
view(
    writer,
    new
    {
        navigation = navigation,
    },
    // ???
);

But what do I pass as a third argument to the template to preserve the values in options.Data? I've tried passing options.Frame, but that results in the runtime crapping itself with

BadImageFormatException: An attempt was made to load a program with an incorrect format. (0x8007000B)

[oformaniuk]

I have not check my theory but it looks like you're using wrong CompileView overload. You should use a different one:

HandlebarsTemplate<TextWriter, object, object> CompileView(string templatePath, ViewReaderFactory readerFactoryFactory)

For a reference you can look at the following test: CanLoadAWriterViewWithALayout

Regarding passing a @data object to a child template I'm not sure that it's possible/easy to do assuming current implementation as DataValues does not expose any information regarding existing values.
Without changing implementation you can access ContextDataObject property of options.Frame using reflation and pass it's value as a third argument. However I'd probably not recommend using this approach for a long run as it may be broken in future updates.

A simple change to fix the problem can be made: expose Keys (or any better name) from DataValues to allow constructing new @data object when needed.

[oformaniuk]

@heemskerkerik , alternatively you can look at making HandlebarsCompiler public and use its CompileView. This can give you a better control and you'd be able to execute navigation view in child context omitting the need to pass @data object at all.