Erroneous red flagging of blank lines when merging covered file results with uncovered file results

[ksmurphy]

SimpleCov 0.11.1: This error occurs when using rspec and cucumber in two different runs and expecting them to be properly merged and an accurate map displayed. I'm confident it occurs in similar situations as well.

To reproduce:

1. Run rspec tests using SimpleCov such that it will flag some of the lines in a ruby file as having been executed.
2. Run cucumber using SimpleCov such that that same ruby file is covered, but no lines in it are actually executed.
3. Note that in .resultset.json the rspec section for this ruby file consists of nil, 0 and 1 values, while the cucumber section for this file consists of all 0's.
4. Note that the resultant report, showing the merged results, highlights all non-executed lines of code in red, including blank and comment lines. Obviously the file and project test coverage stats are also wrong.

I believe this is because of faulty logic in line 7 of lib/simplecov/merge_helpers.rb. It reads
if element.nil? && new_array[i].nil?
when it should read
if element.nil? || new_array[i].nil?

The original logic (see context) allows a 0 to wipe out the nil which serves as a comment indicator, erroneously replacing it with a 0, resulting in erroneous red highlighting of comments and blank lines.

You can create a logic table to see why the original code is faulty and this fix corrects it.

When I make this change the error goes away.

If I get time I'll make this correction and submit a PR. But I wanted others to know about this in case they need a quick fix before I can get to it.

You can just edit the code in place for a quick fix. You can do a "gem which simplecov" on your console to find the code location.

[danishsatkut]

This is definitely an issue and the provided solution works. Thanks 💯

[chriskottom]

+1 for this fix. It seems to have worked in my env - Ruby 2.2.3, SimpleCov 0.11.2.

[rdunlop]

I suspect that this is fixed by #441

[fighterii]

I can confirm that the fix suggested did it for me

[PragTob]

Seems this was fixed by #441 - thanks! :)