JSX - Only inline single expressions when the parent element contains text

Extracted from https://github.com/prettier/prettier/pull/1831

Currently we always inline JSX if the element just contains a single expression:

<div>{variable}</div>

Generally there seems to be a preference to format the above as:

<div>
  {variable}
</div>

But we still want to allow inlining expressions when the parent element contains text.

// The expression can stay inlined here
<div>
  First <span>{variable}</span>
</div>

I’d need some time to investigate the approach, as I don’t currently know how to pass information about a parent element (whether it contains text) down to the child elements.

[karl]

I should be able to spent a little time on it tomorrow. I’ll see what I can come up with!

[karl]

@vjeux path.getParentNode() made this fix nice and easy 😀