Emulate SafeString somehow

[thumphries]

In Handlebars, SafeStrings are values you can construct that don't get escaped when they appear in a mustache. Apparently we might need them

It's easy enough to add it to Value but will need to rejig BMX.Eval a little bit, as escaping happens after the type has been erased

@damncabbage if you could provide an example of how we'd be using them (generating them from a helper, I presume) that'd help

[damncabbage]

Sure.

A simple example from the handlebars docs:

Handlebars.registerHelper('link', function(text, url) {
  text = Handlebars.Utils.escapeExpression(text);
  url  = Handlebars.Utils.escapeExpression(url);
  var result = '<a href="' + url + '">' + text + '</a>';
  return new Handlebars.SafeString(result);
});

And a probable use for us, based on numberListToJS I'm trying in https://github.com/ambiata/bikeshed/pull/71:

// JSON -> SafeString
// eg. ["Nokia","Samsung","Mozilla"] => '["Nokia", "Samsung", "Mozilla"]'
handlebars.registerHelper('toJSLiteral', function(x) {
  return new handlebars.SafeString(JSON.stringify(x));
});

(This is a bit extreme, but an extension of the numberListToJS, stringListToJS, numberToJS, etc. set of helpers I see coalescing to help provide seed data to the graph (and other) script blocks. The Haskell version of this particular example would be taking advantage of the round-trippability-to/from-JSON nature of the Value type.)

^{Edit: I can hear @charleso's small scream of horror from here.}

[thumphries]

Something I don't quite get about either one - why not just call it with an unescaped mustache, like {{{ link "http://blah" }}}? I am probably still missing something...

Value doesn't have a JSON instance anymore. You'd probably use the ToJSON instances of the boxed types instead (Text Integer Bool etc), and use those directly in your helper. I see how you'd want raw JSON output to be unescaped, though.

[damncabbage]

Fair point about {{{ ... }}}s; we can use those in our implementation, and leave the {{ returnsSomeHtml }}-style helpers as an unimplemented todo compatibility item.

[thumphries]

@damncabbage don't need this anymore, do we?