Recusive variable resolving

[montoner0]

Hi!
Is there some easy way to recursively resolve a variable?
E. g. when template {{ variable1 }} with variable1="{{ variable2 }}" and variable2="value" resolves to value.
For now, the only way I see is doing parse-render in a cycle.

[marcel-hofer]

If you want this behavior globally - I would probably use the same approach you mentioned.

We had a similar requirement but the re-rendering was limited to a few variables.
Our templates were translated using resources and some of them contained placeholders. For those translations (we managed them), we added a filter to replace the variables. Usage: {{ variable1 | template }}

It is not recursive but is already sufficient for many use cases like the example you mentioned.

public string Render<TModel>(string template, TModel model)
{
    var parser = new FluidParser();
    if (!parser.TryParse(template, out var compiledTemplate, out var error))
    {
        throw new TemplateParseException(error, template);
    }

    var templateOptions = new TemplateOptions
    {
        MemberAccessStrategy = new UnsafeMemberAccessStrategy(),
    };
    templateOptions.Filters.AddFilter("template", TemplateFilter);

    var context = new TemplateContext(model, templateOptions);
    var result = compiledTemplate.Render(context);

    return result;
}

private ValueTask<FluidValue> TemplateFilter(
    FluidValue input,
    FilterArguments arguments,
    TemplateContext context)
{
    var template = input.ToStringValue();

    if (!fluidParser.TryParse(template, out var compiledTemplate, out var error))
    {
        throw new TemplateParseException(error, template);
    }

    var result = compiledTemplate.Render(context);
    return new ValueTask<FluidValue>(new StringValue(result));
}

public class TemplateParseException : Exception
{
    public TemplateParseException(string message, string template)
        : base(message)
    {
        Template = template;
    }

    public string Template { get; set; }
}

Usage:

var model = new { Format = "Hello, {{ Name }}", Name = "John" };
const string template = "{{ Format | template }}!";

// Returns "Hello, John!"
var result = Render(template, model);