fix: the occasional staking module `SimulateMsgCancelUnbondingDelegat…

…e` failure (#12933)

## Description


---
This is a temporary fix targeted at staking module simulation for #12931.
We should randomly choose the unbonding entry `CreationHeight`, and then fetch the first entry that matches the `CreationHeight` to make sure we can get the correct entry balance.
### Author Checklist

*All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.*

I have...

- [ ] included the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] added `!` to the type prefix if API or client breaking change
- [ ] targeted the correct branch (see [PR Targeting](https://github.com/cosmos/cosmos-sdk/blob/main/CONTRIBUTING.md#pr-targeting))
- [ ] provided a link to the relevant issue or specification
- [ ] followed the guidelines for [building modules](https://github.com/cosmos/cosmos-sdk/blob/main/docs/building-modules)
- [ ] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/main/CONTRIBUTING.md#testing)
- [ ] added a changelog entry to `CHANGELOG.md`
- [ ] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [ ] updated the relevant documentation or specification
- [ ] reviewed "Files changed" and left comments if necessary
- [ ] confirmed all CI checks have passed

### Reviewers Checklist

*All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.*

I have...

- [ ] confirmed the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] confirmed `!` in the type prefix if API or client breaking change
- [ ] confirmed all author checklist items have been addressed 
- [ ] reviewed state machine logic
- [ ] reviewed API design and naming
- [ ] reviewed documentation is accurate
- [ ] reviewed tests and test coverage
- [ ] manually tested (if applicable)

go.work.sum

@@ -3,6 +3,7 @@ cosmossdk.io/math v1.0.0-beta.3.0.20220726092710-f848e4300a8a/go.mod h1:3LYasri3
 github.com/ChainSafe/go-schnorrkel v0.0.0-20200405005733-88cbf1b4c40d h1:nalkkPQcITbvhmL4+C4cKA87NW0tfm3Kl9VXRoPywFg=
 github.com/DATA-DOG/go-sqlmock v1.5.0 h1:Shsta01QNfFxHCfpW6YH2STWB0MudeXXEWMr20OEh60=
 github.com/DataDog/zstd v1.5.2/go.mod h1:g4AWEaM3yOg3HYfnJ3YIawPnVdXJh9QME85blwSAmyw=
+github.com/Workiva/go-datastructures v1.0.53 h1:J6Y/52yX10Xc5JjXmGtWoSSxs3mZnGSaq37xZZh7Yig=
 github.com/Zilliqa/gozilliqa-sdk v1.2.1-0.20201201074141-dd0ecada1be6/go.mod h1:eSYp2T6f0apnuW8TzhV3f6Aff2SE8Dwio++U4ha4yEM=
 github.com/btcsuite/btcd v0.0.0-20190315201642-aa6e0f35703c/go.mod h1:DrZx5ec/dmnfpw9KyYoQyYo7d0KEvTkk/5M/vbZjAr8=
 github.com/btcsuite/btcutil v0.0.0-20190207003914-4c204d697803/go.mod h1:+5NJ2+qvTyV9exUAL/rxXi3DcLg2Ts+ymUAY5y4NvMg=

x/staking/simulation/operations.go

@@ -413,8 +413,22 @@ func SimulateMsgCancelUnbondingDelegate(ak types.AccountKeeper, bk types.BankKee
 			return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgCancelUnbondingDelegation, "account does have any unbonding delegation"), nil, nil
 		}
 
-		// get random unbonding delegation entry at block height
-		unbondingDelegationEntry := unbondingDelegation.Entries[r.Intn(len(unbondingDelegation.Entries))]
+		// This is a temporary fix to make staking simulation pass. We should fetch
+		// the first unbondingDelegationEntry that matches the creationHeight, because
+		// currently the staking msgServer chooses the first unbondingDelegationEntry
+		// with the matching creationHeight.
+		//
+		// ref: https://github.com/cosmos/cosmos-sdk/issues/12932
+		creationHeight := unbondingDelegation.Entries[r.Intn(len(unbondingDelegation.Entries))].CreationHeight
+
+		var unbondingDelegationEntry types.UnbondingDelegationEntry
+
+		for _, entry := range unbondingDelegation.Entries {
+			if entry.CreationHeight == creationHeight {
+				unbondingDelegationEntry = entry
+				break
+			}
+		}
 
 		if unbondingDelegationEntry.CompletionTime.Before(ctx.BlockTime()) {
 			return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgCancelUnbondingDelegation, "unbonding delegation is already processed"), nil, nil