Error in tab expansion results in white-space of incorrect size

[MarkMaldaba]

Hi there,

I have just upgrade from CodeSniffer 1.x to 2.x and have come across what appears to be a bug in the way tabs are expanded. As far as I can see, this has existed since 2.0 and still exists in the latest 2.8 version. I have not tested on 3.x.

Consider the following (invalid, but illustrative) line in a file:
123 56 (the gap in the middle is a tab character, i.e. 123\t56)

Expected result (assuming a tab-width of 4 characters):

• Translated content: " " (single space character)
• Reported line length = 6

Actual result:

• Translated content: "     " (5 space characters)
• Reported line length = 10

As far as I can see, the problem is in the calculation of $firstTabSize in Files.php on line 1542.
Instead of:

$firstTabSize = ($tabWidth - ($currColumn % $tabWidth) + 1);

it should be

$firstTabSize = ($tabWidth - (($currColumn - 1) % $tabWidth));

The reason I spotted this was because I suddenly started getting errors from Generic.Files.LineLength.MaxExceeded which I wasn't getting prior to the upgrade.

I am surprised no-one else has spotted this issue - I know this code path is only travelled for white-space composed entirely of tabs, but I wouldn't expect that to be particularly uncommon.

[orlangur]

I am surprised no-one else has spotted this issue

With PSR-2 expansion tabs could be met rarely in source code whilst LineLength.MaxExceeded is just a warning in it :) Also, meeting such error there is a reflex just to change the line instead of calculating whether PHPCS calculation is correct or not. Nice boundary check!

[gsherwood]

Thanks a lot for reporting and fixing this. It is strange that it has never come up, but was clearly wrong on those tab boundaries.

[MarkMaldaba]

:-) No problem. Thanks for accepting it so quickly.