Layout/SpaceAroundMethodCallOperator is slow

[marcandre]

This cop inspects in O(n^2) instead of O(n) as it should (culprit is this loop) (where n is the order of send nodes / tokens)

As an example, about 10% of rake internal_investigation is currently spent in this cop alone. This would be way worse if the source files were not kept kind of small.

@saurabhmaurya15 would you like to look at this? Using tokens may have been a nice generic way of handling things but we can't afford it. We must use node.loc.

[marcandre]

Note: one could use token(node).find as a quick improvement for processed_source.find_token, but ideally this could be done without tokens I think

[saurabhmaurya15]

@marcandre Can you help me out with how you did profiling on this? I can give it a shot then.

[marcandre]

I need to create a rake task to do this properly, but I want to finish #7868 beforehand. In the meantime there's a rake task for testing a particular cop you could use. If you manage not to use tokens at all it would be a big improvement. Or wait a few days and there will be a rake task to measure the cops...

[ric2b]

Also ran into the same issue, enabling this cop pushed rubocop runs (cache disabled) from ~1 or 2 minutes to over 20 minutes on my codebase.

It took a bit or work to figure out the culprit (doing bisection with --except) because the debug option (-d) only shows which files are being evaluated, it would be nice to have a "verbose debug" option that also printed which cops were running.