Clear callbacks whenever files are changed during dev / test, to fix issue with Spring

[ndbroadbent]

Fixes #136.

Spring doesn't provide any hooks for reloaded files, so I used the listen gem for this. Before this, I would always have to run spring stop whenever I changed a model, because Spring would reload the models and add duplicate callbacks for stripe-rails. Everything works for me after this change, and my tests always start very quickly.

If people are not using Spring, then this change will do nothing. (I call: defined? ::Spring::Application && defined? Listen)

One very minor issue: I was able to trigger a race condition when I saved a file right when the tests started. This cleared all the callbacks after Spring had already reloaded the models, so my tests failed. But it worked when I ran the tests a second time.

[ndbroadbent]

Sorry, I finally figured out the right way to do this. This was actually a problem with the code reloading in Rails development, and Spring just meant that it affected my tests as well.

The Rails Reloader provides an after_class_unload hook that I can use to clear all the callbacks before all the models are reloaded.

My initial attempt was a lot of code that set up manual file listeners, but I just needed this after_class_unload hook to clear all the callbacks before the models were reloaded.

[tansengming]

Hi @ndbroadbent thanks for looking into this! It looks like it'll make a bunch of folks happy. I just need two more things before I merge this,

1. it looks like it's failing on Rails 4 tests, could you add a guard for this please? Thanks!
2. how should I manually test this? Should I just update a model with a stripe callback and see if it gets updated? Any tips would be helpful.

[tansengming]

and thanks for sharing the link to the Reloader, this is a part of Rails that I didn't know about.

[ndbroadbent]

Hi @tansengming, sorry I didn't see those broken tests! Should be fixed now. I couldn't see an easy way to do this in Rails 4 so I've just skipped it for now.

To test it, I've been adding a puts statement inside the after_class_unload block, and just confirming that it was called after I change a model and make a request.

I also learned quite a bit about the Rails reloading during development. When you change any file, Rails actually unloads all of the models/controllers/etc. and reloads all the files. I had assumed it was more fine-grained than that, but it just blows everything away, so it's safe to call clear_callbacks! here.

[tansengming]

I couldn't see an easy way to do this in Rails 4 so I've just skipped it for now.

No worries! Let's leave that for other developers to take a crack at 😄

I'll run a quick test later in the day before merging this. Thanks for this!

[tansengming]

I've been trying to reproduce #136 with tansengming/stripe-rails-dummy#1 without much luck.

@ndbroadbent any idea what I'm doing wrong?

This PR looks good by the way but it's curious that I'm not seeing the same issue.

[tansengming]

The testing issue was handled on tansengming/stripe-rails-dummy#1 thanks for all the help!