are dust helper dependencies bundled within compiled templates?

Question

I'm wondering how helper dependencies are managed in compiled dust templates, specifically relating to being used on the client -- is the helper method bundled with the compiled dust template? What about dependencies that might not be supported on the client? Or if that dependency has multiple other dependencies?

Here's a trivial example of a dust template I'd like to be able to use on the client:

// foo.dust
{@myHelper}
  <div>{foo}{bar}</div>
{/myHelper}


// my-helper.js
const isomorphicDep = require('isomorphic-dep');
const nodeDep = require('node-dep');

module.exports = function(dust) {
  dust.helpers.myHelper = function(chunk, context, bodies, params) {
    // do some stuff using deps
    let foo = nodeDep.getFoo();
    let bar = isomorphicDep.getBar(params.someInput);

    return chunk.render(bodies.block, context.push({ foo, bar });
  };
};

Thanks

Answer 1

A compiled template just contains instructions for how to render-- it does not include any client code itself.

For example, a simple template like this:

{@helper}foo{/helper}

Compiles into these two instruction sets:

function body_0(chk, ctx) {
  return chk.h("helper", ctx, {
    "block": body_1
  }, {}, "h");
}

function body_1(chk, ctx) {
  return chk.w("foo");
}

When the template is rendered, it asks Dust to look for the helper named helper and execute it (in the body_0 function). The code for helper is not included with the template.

So on the client, you'll need to include a file containing the helper that loads the correct isomorphic dep (like node-fetch vs whatwg-fetch, for example).