Add SafeString to context (or use duck-typing)

[dominicbarnes]

Hey there, I'm having trouble with one aspect of using handlebars in a node setting.

When I want to share helpers from various places, and I want to use handlebars.SafeString, I am finding it difficult, since the instanceof check will only pass if the SafeString object came from the local instance. With node, there could be several versions of handlebars installed, but only the local one passes.

Passing around a single instance of handlebars to all of these modules is not ideal, especially for such a trivial thing. I have a few proposals (in order of preference/ease-of-implementation)

1. add SafeString to the context of the helper, so I don't need any other external reference for it to work:

exports.myHelper = function (options) {
  return new options.SafeString("foo");
};

2. use duck-typing within Utils.escapeExpression, rather than (or in addition to) instanceof:

} else if (typeof string === "object" && typeof string.string === "string") {
  // this test may not be accurate, this is just an example
}

3. execute helpers using the handlebars instance as this

exports.myHelper = function () {
  return new this.SafeString("foo");
};

For now, I can just use {{{ to accomplish what I need. So, this is not "urgent", but I would like to start the discussion. :)

[dominicbarnes]

As another thought on option 1: if SafeString is added to the exports of Utils, perhaps all of Utils could be added to the context?

exports.myHelper = function (string, options) {
  var substring = options.utils.escapeExpression(string);
  return new options.utils.SafeString("<b>" + myString + "</b>");
};

I actually have a specific helper in mind that would use both of these methods... and this would be awesome to have.

[kpdecker]

We can look into the duck typing option. I've never really liked instanceof and it does get really bad in Node. (You can handle some of this in a bit safer manner by using npm dedupe but this does not always work)

Right now I'm considering adding a toHTML method to SafeString so that any object implementing this can control their own flow. I need to decide if this is a breaking change or not as it may cause issues in the event that an object is passed currently that implements a toHTML method.

[kpdecker]

Closing in favor of #890.