Adding frame variables from custom tag

I’m trying to make an extension which adds support for the trans tag. Jinja trans syntax requires you to bind template expressions to new variables via keyword arguments, like:

<p>{% trans user=user.username %}Hello {{ user }}!{% endtrans %}</p>

Now, I’m able to iterate over the arguments to my tag and add them to the context like this:

    this.run = function(context, args, body) {
        for (key in args) {
            context.ctx[key] = args[key];
        }
        return gettext(body()); # gettext() is defined somewhere else.
 }

But it seems I’m getting the global context and polluting this, which leaves my new variables available outside my trans tag (i.e. the user variable will be available everywhere afterwards).

How do I extend only the “local” context used by my tag? It seems the for and (in some cases) set tags do this and I tried looking through the source for this, but I’m unfortunately lost.

[KSDaemon]

Hi all, guys! Just faced the same kind of problem. I’m creating format.js internationalization helper for nunjucks templater. And one last thing i have to implement — is a custom ‘intl’ tag, that overrides global intl locale options provided. For ex., you can render whole template, using a ‘en’ locale, but have one block with ‘fr’ locale. Unfortunately, docs about hijacking nunjucks extensions api is very poor, but i’ve got somehow through sources, and have come to this.

What about adding access to frame stack through some method in ctx, like lookup? For example:

// inside run function of custom extension:
var frame = context.addFrame();
frame.set('my-scoped-var', 'scoped-value');

return content();

Or just allow raw access to frames stack, so developer can use push/pop and all other frame methods.

var frame = context.frames.push();

[djx314]

+1