Add line break before forced space to stay within the print width

[mariusschulz]

Prettier 1.12.1
Playground link

Input:

const someVariable = (
  <div>
    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx{" "}y
  </div>
);

Output:

const someVariable = (
  <div>
    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx{" "}
    y
  </div>
);

Expected behavior:

const someVariable = (
  <div>
    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
    {" "}y
  </div>
);

With --print-width=80, the forced space ({" "}) should be placed on the next line so that the line does not exceed the print width.

[duailibe]

Context: #1582 #1831 #1964

We decided to do always append to the preceding node (instead of prepending to the following node) because there might be some cases of

<div>
  xxxxxxxxxxxx
  {" "}<div>
    <Something />
  </div>
</div>

I guess we can improve this heuristic, see what's before and what's after and then chose what's best.

[lydell]

I actually think this is a duplicate of #2553