Significant performance degradation in super_diff 0.8

[hedgesky]

Hi @mcmire,
thank you a lot for an amazing gem! It removed a lot of pain from working with some of the specs we have in the codebase.

I noticed that after upgrading super_diff to 0.8 our test suite slowed down by 4x (from ≈30s to 2m). Downgrading to 0.7 resolves the issue.

I ran some profiling and tried to analyse execution path, and it looks like the issue appeared after merging #91. Profiling showed that majority of the time is spent in SuperDiff::ObjectInspection::InspectionTree#render_to_string.

I tried to understand what's going on and how it would be possible to avoid that, but wasn't able to, unfortunately.

Attaching the profiling screenshot:

[mcmire]

Hi @hedgesky,

Sorry for taking so long to reply to this issue. It initially surprised me to hear that the gem decreased performance because it really should only kick in when a test fails, but after looking at your screenshot, I'm realizing that the gem monkeypatches the description for each built-in RSpec matcher, so every time RSpec accesses a description it'll go through some logic here in the gem. I would imagine that some simple tricks can be applied to the inspection logic to fix the performance issue. Anyway, thank you for reporting this. I admit that I've been lax in tending to this gem lately due to life, but I will try to make an effort to take a closer look at this soon.