* Allow --debug-check to work with stdin
This makes it easier to quickly test formatting code snippets with e.g.
pbpaste | prettier --debug-check
Before, the following would happen:
$ pbpaste | prettier --debug-check
stdin: TypeError: Invalid data, chunk must be a string or buffer, not undefined
at WriteStream.Socket.write (net.js:693:11)
at writeOutput (/Users/josephfrazier/workspace/prettier/bin/prettier.js:375:18)
at getStdin.then.input (/Users/josephfrazier/workspace/prettier/bin/prettier.js:275:7)
at <anonymous>
at process._tickCallback (internal/process/next_tick.js:169:7)
$
Now, it looks like this:
$ pbpaste | prettier --debug-check
(stdin)
$
* Test that --debug-check still prints filenames
See https://github.com/prettier/prettier/pull/2013#discussion_r120499306