Leave interpreting attribute values to the renderer

[slaskis]

This is a PR for #27 which changes the default behaviour of attribute values.

Now it will leave the interpreting of the attribute values to the renderer, such like <div x=${null}></div> will pass attributes as {x: null} to the renderer instead of {x: 'null'} as it does before this PR.

An important note may be that null and undefined as values, with virtual-dom (^2.1.1), removes the attribute entirely, while false instead throws an exception because it attempts to do some entity serialization.

Behaviour is different using hyperscript which simply makes an attribute with an empty string value instead.

[slaskis]

Because of the potentially breaking changes I'm thinking this might need a semver bump to 3.x.x

[jorgebucaran]

Hi @substack @JamesKyburz 👋

Do you have any plans to merge this?

[dereke]

This is a pretty major issue in hyperx in my opinion.
It is definitely worth bumping the version and getting it out.

[casr]

I think if you pass a plain object to the tag it passes it on to the renderer. Your example would be rewritten as:

<div ${{x: null}}></div>

Or a full example from something I was working on recently (notice the selected attribute):

const hx = require('hyperx')(require('virtual-dom/h'))

module.exports = ({changeHandler, label, options, selected}) => {
  return hx`
  <div>
    <label>${label}
      <select onchange=${changeHandler}>
        ${options.map((option) => hx`
          <option
            value=${option.id}
            ${{selected: selected.id === option.id}}
          >
            ${option.name}
          </option>`
        )}
      </select>
    </label>
  </div>`
}