Line wrapping breaks at the wrong place when the line is indented.

[seronal]

The problem is related to indentation. It's as if js-beautify "double counts" indent spaces while calculating where to break the line.

If you beautify the following code with "wrap_line_length" set to 80, dummy2 and dummy3 lines get wrapped even though they should not. There are the same number of B's in each string as the number of indent spaces in that line and if you remove all the B's from those strings they won't be wrapped.

This bug does not exist in version 1.5.1, but it exists in every version released since.

var dummy = 'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA';

function dummyFunction() {
    var dummy2 = 'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABBBB';

    function dummyFunction2() {
        var dummy3 = 'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABBBBBBBB';
    }
}

Output from jsbeautifier.org

var dummy = 'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA';

function dummyFunction() {
    var dummy2 =
        'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABBBB';

    function dummyFunction2() {
        var dummy3 =
            'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABBBBBBBB';
    }
}

[redapple]

I sort of managed to follow this with a bunch of print statements.
It looks related to TK_WORD, 'dummyFunction' + TK_START_EXPR, '(' starting an expression handled in handle_start_expr(), but also indenting (see start_of_statement call at the beginning of handle_start_expr())

In [5]: t = r'''var dummy = 'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA';

function dummyFunction() {
    var dummy2 = 'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABBBB';

    function dummyFunction2() {
        var dummy3 = 'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABBBBBBBB';
    }
}'''

In [6]: print jsbeautifier.beautify(t, opts)
__character_count=0
__character_count=0
('TK_RESERVED', 'var')
start_of_statement: self.last_type 'TK_START_BLOCK', self.flags.last_text ''; self.flags.mode 0
print_token_line_indentation
Output::set_indent(level=0)
OutputLine::set_indent(level=0)
__character_count(0) = __parent.baseIndentLength(0) + level(0) * __parent.indent_length(4)
__character_count(3) += 3 (`var`)
('TK_WORD', 'dummy')
start_of_statement: self.last_type 'TK_RESERVED', self.flags.last_text 'var'; self.flags.mode 0
start_of_statement: self.indent()
indent: self.flags.indentation_level=1
proposed_line_length 8 = self.output.current_line.get_character_count() 3 + len(current_token.text) 5
print_token_line_indentation
__character_count(4) += 1 (` `)
__character_count(9) += 5 (`dummy`)
('TK_EQUALS', '=')
start_of_statement: self.last_type 'TK_WORD', self.flags.last_text 'dummy'; self.flags.mode 1
print_token_line_indentation
__character_count(10) += 1 (` `)
__character_count(11) += 1 (`=`)
('TK_STRING', "'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA'")
start_of_statement: self.last_type 'TK_EQUALS', self.flags.last_text '='; self.flags.mode 1
proposed_line_length 78 = self.output.current_line.get_character_count() 11 + len(current_token.text) 67
proposed_line_length += 1 (79)
print_token_line_indentation
__character_count(12) += 1 (` `)
__character_count(79) += 67 (`'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA'`)
('TK_SEMICOLON', ';')
start_of_statement: self.last_type 'TK_STRING', self.flags.last_text "'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA'"; self.flags.mode 1
restore_mode: self.flags.indentation_level=0
print_token_line_indentation
__character_count(80) += 1 (`;`)
('TK_RESERVED', 'function')
__character_count=0
__character_count=0
start_of_statement: self.last_type 'TK_SEMICOLON', self.flags.last_text ';'; self.flags.mode 0
print_token_line_indentation
Output::set_indent(level=0)
OutputLine::set_indent(level=0)
__character_count(0) = __parent.baseIndentLength(0) + level(0) * __parent.indent_length(4)
__character_count(8) += 8 (`function`)
('TK_WORD', 'dummyFunction')
start_of_statement: self.last_type 'TK_RESERVED', self.flags.last_text 'function'; self.flags.mode 0
print_token_line_indentation
__character_count(9) += 1 (` `)
__character_count(22) += 13 (`dummyFunction`)
('TK_START_EXPR', '(')
start_of_statement: self.last_type 'TK_WORD', self.flags.last_text 'dummyFunction'; self.flags.mode 0
start_of_statement: self.indent()
indent: self.flags.indentation_level=1
proposed_line_length 23 = self.output.current_line.get_character_count() 22 + len(current_token.text) 1
print_token_line_indentation
__character_count(23) += 1 (`(`)
handle_start_expr: self.indent() #2
indent: self.flags.indentation_level=2
('TK_END_EXPR', ')')
restore_mode: self.flags.indentation_level=1
print_token_line_indentation
__character_count(24) += 1 (`)`)
('TK_START_BLOCK', '{')
print_token_line_indentation
__character_count(25) += 1 (` `)
__character_count(26) += 1 (`{`)
handle_start_block: self.indent()
indent: self.flags.indentation_level=2
('TK_RESERVED', 'var')
start_of_statement: self.last_type 'TK_START_BLOCK', self.flags.last_text '{'; self.flags.mode 0
__character_count=0
print_token_line_indentation
Output::set_indent(level=2)
OutputLine::set_indent(level=2)
__character_count(8) = __parent.baseIndentLength(0) + level(2) * __parent.indent_length(4)
__character_count(11) += 3 (`var`)
('TK_WORD', 'dummy2')
start_of_statement: self.last_type 'TK_RESERVED', self.flags.last_text 'var'; self.flags.mode 0
start_of_statement: self.indent()
indent: self.flags.indentation_level=3
proposed_line_length 17 = self.output.current_line.get_character_count() 11 + len(current_token.text) 6
print_token_line_indentation
__character_count(12) += 1 (` `)
__character_count(18) += 6 (`dummy2`)
('TK_EQUALS', '=')
start_of_statement: self.last_type 'TK_WORD', self.flags.last_text 'dummy2'; self.flags.mode 1
print_token_line_indentation
__character_count(19) += 1 (` `)
__character_count(20) += 1 (`=`)
('TK_STRING', "'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABBBB'")
start_of_statement: self.last_type 'TK_EQUALS', self.flags.last_text '='; self.flags.mode 1
proposed_line_length 82 = self.output.current_line.get_character_count() 20 + len(current_token.text) 62
proposed_line_length += 1 (83)
__character_count=0
print_token_line_indentation
Output::set_indent(level=3)
OutputLine::set_indent(level=3)
__character_count(12) = __parent.baseIndentLength(0) + level(3) * __parent.indent_length(4)
__character_count(74) += 62 (`'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABBBB'`)
('TK_SEMICOLON', ';')
start_of_statement: self.last_type 'TK_STRING', self.flags.last_text "'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABBBB'"; self.flags.mode 1
restore_mode: self.flags.indentation_level=2
print_token_line_indentation
__character_count(75) += 1 (`;`)

[bitwiseman]

@redapple - I'm having trouble following your print statement debugging, but thanks for trying.
@seronal - The word wrap is very approximate. In this case, it looks like a bug that can/should be fixed. I'd just like to set expectation here that, even when this particular case is fixed, there will be many other cases where wrap will occur sooner than you might expect.

[seronal]

@bitwiseman I totally understand that wrap might occur sooner than the exact column if line length is longer than "wrap_line_length". However, this is a different case. Per my understanding of the specification; a line should never be wrapped if it's shorter than "wrap_line_length", i.e. there should not be any approximation/uncertainty about whether to wrap, but only where to wrap.

[bitwiseman]

a line should never be wrapped if it's shorter than "wrap_line_length"

No, unfortunately. At this time, we have a process of indenting where we indent all blocks, and when a block closes we look at the contents and remove the redundant indents. This results in some cases where we will indent before expected.

Note: this was not one of those cases and is now fixed.
But...

(function() {
    var dummy2 = 'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABBBB';
    var dummy3 = 'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABBBBBBBB';
})

// This has an intermediate state that looks like this
(function() {
        var dummy2 = 'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABBBB';
        var dummy3 = 'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABBBBBBBB';
})

// At the end the enclosing (), the beautifier removes the extra indent, 
// but it doesn't currently have the functionality to go back and re-evaluate all the line wraps.
// The result is this:
(function() {
    var dummy2 =
        'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABBBB';
    var dummy3 = 'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABBBBBBBB';
})

That is unfortunate, but a known issue -

This on the other hand, is a new bug.

dummyFunction(function() {
    var dummy2 = 'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABBBB';
    var dummy3 = 'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABBBBBBBB';
})

// Second line should really not wrap, but does... 
// There still an extra intermediate indent in here somewhere.
dummyFunction(function() {
    var dummy2 =
        'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABBBB';
    var dummy3 = 
        'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABBBBBBBB';
})