Javascript multiline comments duplicates

[D-AIRY]

Description

Javascript multiline comments duplicates

Input

The code looked like this before beautification:

	/* comment
	
	*/

Expected Output

The code should have looked like this after beautification:

	/* comment
	
	*/

Actual Output

The code actually looked like this after beautification:

	/* comment
	/* comment
	
	*/
	*/

Steps to Reproduce

1. go to https://beautifier.io/
2. use following code with default options:

\t/* comment\n
\t\n
\t*/\n

Environment

OS: windows 7

Settings

Example:

{
    "indent_size": 4,
    "indent_char": " ",
    "indent_level": 0,
    "indent_with_tabs": true,
    "preserve_newlines": true,
    "max_preserve_newlines": 10,
    "jslint_happy": false,
    "space_after_anon_function": false,
    "brace_style": "collapse,preserve-inline",
    "keep_array_indentation": false,
    "keep_function_indentation": false,
    "space_before_conditional": true,
    "break_chained_methods": false,
    "eval_code": false,
    "unescape_strings": false,
    "wrap_line_length": 0
}

[bitwiseman]

@D-AIRY
I can't reproduce this issue. Is the settings text above what was shown on the site?
What browser are you using?

[D-AIRY]

Try this file:
bug.txt
Ensure you have tab charated in lines 1-3 and empty line 4
Also reproducible with default settings.
Tested in latest firefox and ios safari

[bitwiseman]

@D-AIRY
wow. Great bug. Thanks!

[bitwiseman]

NOTES:

Also happens with:

 /* one space before each line
 
 */

The problem is that blank line is being turn into an empty string and passed to print_token.

https://github.com/beautify-web/js-beautify/blob/d88c6a64620c3e795ff34344029e00941f1e297a/js/src/javascript/beautifier.js#L1372

In there we have this line:

https://github.com/beautify-web/js-beautify/blob/d88c6a64620c3e795ff34344029e00941f1e297a/js/src/javascript/beautifier.js#L429

Which doesn't distinguish between empty string and null, but it should.

This hasn't been run into more because usually blank lines get turned into empty lines.