Ran into a strange issue at work where resolving gems in a bundle (not installing) was taking 3-5 minutes. It was not always this way, and it's unclear what is going on, but we did find a way to fix it that you'd never expect!
BUNDLER: Finished resolution (98145 steps) (Took 212.483564 seconds) (2022-09-15 13:48:59 -0400)
this was a gem, and had a dev dependency on rack AND a non-dev dependency on rails. Seems like rails will include rack anyway. Removing s.add_development_dependency('rack') changed the behavior like so:
BUNDLER: Finished resolution (289 steps) (Took 1.206765 seconds) (2022-09-15 14:11:36 -0400)
This same behavior has been verified on bundler versions 2.3.11 and 2.3.22
rack 3.0.0 was released Sept 6th 2022 (today is Sept 15). This may be causing dependency resolution dead end from libraries that have not-yet been updated. Still, the explosion looks exponential and not what I would expect.
Removing the rack dependency reduces the resolution steps dramatically.
Pinning rack to '< 3.0.0' also reduces the resolution steps dramatically.
I think this behavior is exponential (not a linear multiplier) based on my (unsharable) work project taking 100k steps (vs 250 steps). This sample reproduction only hits 800 steps (vs 100 steps).
This could be a pathological behavior that you'd be unlikely to encounter - except that rack is a common dependency and there are surely a combo of projects that are permissive and projects that are pinned to < 3.0.0. In other words: this may or may not be acceptable behavior.
DEBUG_RESOLVER=1 bundle lock --print | grep "Finished resolution"
Do this WITH and WITHOUT the resolution_explosion.gemspec having rack as a dev dependency (it's commented-out by default in this repo).
This reproduction is not as extreme as what I saw in the private project, but still illustrative:
With rack:
➜ resolution_explosion git:(main) ✗ DEBUG_RESOLVER=1 bundle lock --print | grep "Finished resolution"
: 0: Finished resolution (3 steps) (Took 0.00547 seconds) (2022-09-15 17:18:12 -0400)
BUNDLER: Finished resolution (816 steps) (Took 2.0365 seconds) (2022-09-15 17:18:16 -0400)
Without rack:
➜ resolution_explosion git:(main) ✗ DEBUG_RESOLVER=1 bundle lock --print | grep "Finished resolution"
: 0: Finished resolution (3 steps) (Took 0.005878 seconds) (2022-09-15 17:18:30 -0400)
BUNDLER: Finished resolution (123 steps) (Took 0.764866 seconds) (2022-09-15 17:18:33 -0400)