Add warning to feegrant documentation v0.45 and before

[ryanchristo]

Summary

The feegrant module was introduced in v0.44 with a bug when using AllowedMsgAllowance in which case the fee is not subtracted from the spend limit (#10563). This issue has been resolved in #10564 and the changes will be included in v0.46.

Applications using the feegrant module with v0.44 and v0.45 are still affected by the bug meaning spend limit is not updated when using AllowedMsgAllowance and therefore spend limit only limits spending on a per transaction basis and not overall.

This bug should be clearly documented with a warning in the v0.44 and v0.45 feegrant documentation.

Version

v0.44 and v0.45

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[paul121]

This bug should be clearly documented with a warning in the v0.44 and v0.45 feegrant documentation.

v0.44 and v0.45 actually don't include documentation for the AllowedMsgAllowanceallowance type (#11346). This was fixed with #11344 for v0.46 but should be included for these previous versions as well, with additional documentation and warning for the bug.

Considering that v0.46 is not yet released, should the latest version of the docs include a warning describing that previous versions are affected by the bug and will behave differently?

[paul121]

Considering that AllowedMsgAllowance can be one of either BasicAllowance or PeriodicAllowance - as per current docs:

cosmos-sdk/x/feegrant/spec/01_concepts.md

Lines 53 to 61 in 0cc82cf

	## AllowedMsgAllowance
	`AllowedMsgAllowance` is a fee allowance, it can be any of `BasicFeeAllowance`, `PeriodicAllowance` but restricted only to the allowed messages mentioned by the granter.
	+++ https://github.com/cosmos/cosmos-sdk/blob/v0.46.0-rc1/proto/cosmos/feegrant/v1beta1/feegrant.proto#L56-L66
	* `allowance` is either `BasicAllowance` or `PeriodicAllowance`.
	* `allowed_messages` is array of messages allowed to execute the given allowance.

I believe an AllowedMsgAllowance using PeriodicAllowance would have an additional bug that the period_can_spend value would not be updated either. This is effectively the same bug, meaning the spend_limit and period_spend_limit only limits spending on a per-transaction basis and not overall.

So perhaps this warning message can be generalized a bit, maybe something like:

 ## AllowedMsgAllowance 
  
 `AllowedMsgAllowance` is a fee allowance, it can be any of `BasicFeeAllowance`, `PeriodicAllowance` but restricted only to the allowed messages mentioned by the granter.
 
 NOTE: A bug exists in v0.44 and v0.45 where `AllowedMsgAllowance` does not update the state of the `allowance` used. The result of this is that when a `spend_limit` is configured, `AllowedMsgAllowance` will only limit spending on a per transaction basis, and not limit the total number of coins the `grantee` can use from the `granter. More specifically the `spend_limit` will not be updated in neither the `BasicFeeAllowance` nor the `PeriodicAllowance` allowance, and the `period_can_spend` will not be updated in the `PeriodicAllowance`.

Are there any examples of this type of warning in the sdk documentation? If so I'm happy to start a PR for this.

[paul121]

I've just opened an issue and PR for two related bugs in feegrant docs:

#12421
#12422

[alexanderbez]

@AmauryM or @blushi would you by any chance have the ability to look into this?

[tac0turtle]

45 and before is no longer maintained we can close this