Allow nested functions for css prop

[quicksnap]

Glamorous accepts an array for the css prop, which may contain nested arrays of styles. Those styles may be callback functions in order to access the theme:

<Div css={ [myStyle1, myStyle2, ({ theme}) => myStyle3] } />

We currently do not support recursion for the callback's results:

glamorous/src/get-glamor-classname.js

Lines 79 to 86 in d9560fa

	if (typeof current === 'function') {
	const result = current(props, context)
	if (typeof result === 'string') {
	const {glamorStyles, glamorlessClassName} = extractGlamorStyles(result)
	mappedArgs.push(...glamorStyles)
	nonGlamorClassNames.push(...glamorlessClassName)
	} else {
	mappedArgs.push(result)

Would you accept a PR to adjust this? I'm working to make styles functionally composeable, and it would be great if I could return an array with further callback functions!

[quicksnap]

Something like this: https://gist.github.com/quicksnap/c7607d49e2450a25d6208224bc83a668#file-glamorous-js-L13-L19

[kentcdodds]

I've thought about this before. I feel like we might be able to make it simpler. Would this work?

function handleStyles(styles, props, context, mappedArgs = [], nonGlamorClassNames = []) {
  let current
  for (let i = 0; i < styles.length; i++) {
    current = styles[i]
    if (typeof current === 'function') {
      const result = current(props, context)
      handleStyles(result, props, context, mappedArgs, nonGlamorClassNames)
    } else if (typeof current === 'string') {
      const {glamorStyles, glamorlessClassName} = extractGlamorStyles(current)
      mappedArgs.push(...glamorStyles)
      nonGlamorClassNames.push(...glamorlessClassName)
    } else if (Array.isArray(current)) {
      const recursed = handleStyles(current, props, context)
      mappedArgs.push(...recursed.mappedArgs)
      nonGlamorClassNames.push(...recursed.nonGlamorClassNames)
    } else {
      mappedArgs.push(current)
    }
  }
  return {mappedArgs, nonGlamorClassNames}
}

[quicksnap]

Nice! I suppose that means you're receptive to this idea? =P

I'll drum up a PR soon and use that approach