imp: rm app upgrade interface from IBCModule and use type assertions for app callback routing

[damiannolan]

Description

• Removes UpgradableModule from IBCModule interface
• Uses type assertions to cast cbs to UpgradeableModule for app callback routing in core

closes: #1614

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[colin-axner]

LGTM, but would be very lovely with test cases :)

[damiannolan]

LGTM, but would be very lovely with test cases :)

Indeed, I thought about tests but I think the mock app is implementing all the upgrade callbacks. I'd rather not introduce a dependency on some app that doesn't implement the interface yet.
We'd probably need to add another mock app struct somewhere, what do you think?

[damiannolan]

Think we need to cast in the app callbacks as well

[DimitrisJim]

left some comments/nits for your reading delight, lgtm!

[codecov-commenter]

Codecov Report

Merging #5375 (720ed24) into 04-channel-upgrades (e1d4b20) will decrease coverage by 0.24%.
The diff coverage is 35.13%.

❗ Current head 720ed24 differs from pull request most recent head 076aeda. Consider uploading reports for the commit 076aeda to get more accurate results

Additional details and impacted files

@@                   Coverage Diff                   @@
##           04-channel-upgrades    #5375      +/-   ##
=======================================================
- Coverage                80.68%   80.45%   -0.24%     
=======================================================
  Files                      197      197              
  Lines                    14871    14927      +56     
=======================================================
+ Hits                     11999    12009      +10     
- Misses                    2420     2455      +35     
- Partials                   452      463      +11     

Files	Coverage Δ
...7-interchain-accounts/controller/ibc_middleware.go	57.93% <0.00%> (-1.90%)	⬇️
modules/apps/29-fee/ibc_middleware.go	88.27% <44.44%> (-4.70%)	⬇️
modules/core/keeper/msg_server.go	62.22% <33.33%> (-1.89%)	⬇️

[colin-axner]

Indeed, I thought about tests but I think the mock app is implementing all the upgrade callbacks. I'd rather not introduce a dependency on some app that doesn't implement the interface yet.
We'd probably need to add another mock app struct somewhere, what do you think?

I would test by creating a router which points to a mock ibc app which doesn't implement the upgrade module interface. It might be possible to rework the mock package so that it has three types:

• IBCModule
• UpgradeModule
• MockModule (contains both IBCModule and UpgradeModule)