Clarify error message when you try to completely exit a pool (#5165)

* Clarify error message when you try to completely exit a pool

Closes #3427

* Add changelog

CHANGELOG.md

@@ -66,6 +66,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   * [#4974](https://github.com/osmosis-labs/osmosis/pull/4974) Add lock id to `MsgSuperfluidUndelegateAndUnbondLockResponse`
   * [#2741](https://github.com/osmosis-labs/osmosis/pull/2741) Prevent updating the twap record if `ctx.BlockTime <= record.Time` or `ctx.BlockHeight <= record.Height`. Exception, can update the record created when creating the pool in the same block.
   * [#5129](https://github.com/osmosis-labs/osmosis/pull/5129) Relax twap record validation in init genesis to allow one of the spot prices to be non-zero when twap error is observed.
+  * [#5165](https://github.com/osmosis-labs/osmosis/pull/5165) Improve error message when fully exiting from a pool.
 
 ### API breaks
 

x/gamm/pool-models/internal/cfmm_common/lp.go

@@ -11,13 +11,13 @@ import (
 	"github.com/osmosis-labs/osmosis/v15/x/gamm/types"
 )
 
-const errMsgFormatSharesLargerThanMax = "%s resulted shares is larger than the max amount of %s"
+const errMsgFormatSharesLargerThanMax = "cannot exit all shares in a pool. Attempted to exit %s shares, max allowed is %s"
 
 // CalcExitPool returns how many tokens should come out, when exiting k LP shares against a "standard" CFMM
 func CalcExitPool(ctx sdk.Context, pool types.CFMMPoolI, exitingShares sdk.Int, exitFee sdk.Dec) (sdk.Coins, error) {
 	totalShares := pool.GetTotalShares()
 	if exitingShares.GTE(totalShares) {
-		return sdk.Coins{}, errorsmod.Wrapf(types.ErrLimitMaxAmount, errMsgFormatSharesLargerThanMax, exitingShares, totalShares)
+		return sdk.Coins{}, errorsmod.Wrapf(types.ErrLimitMaxAmount, errMsgFormatSharesLargerThanMax, exitingShares, totalShares.Sub(sdk.OneInt()))
 	}
 
 	// refundedShares = exitingShares * (1 - exit fee)