fix!: leverage.MaxBorrow return zero instead of failing when there is no more to borrow

CHANGELOG.md

@@ -49,6 +49,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 ### API Breaking
 
 - [1683](https://github.com/umee-network/umee/pull/1683) MaxWithdraw query now returns `sdk.Coins`, not `sdk.Coin` and will be empty (not zero coin) when returning a zero amount. Denom field in query is now optional.
+- [1694](https://github.com/umee-network/umee/pull/1694) `MsgMaxWithdraw`, `MsgMaxBorrow` and `MsgRepay` won't return errors if there is nothing to withdraw, borrow or repay respectively. Leverage `ErrMaxWithdrawZero` and `ErrMaxBorrowZero` has been removed.
 
 ### Fixes
 
@@ -66,9 +67,9 @@ Ref: https://keepachangelog.com/en/1.0.0/
 - [1685](https://github.com/umee-network/umee/pull/1685) Add medians param to Token registry.
 - [1683](https://github.com/umee-network/umee/pull/1683) Add MaxBorrow query and allow returning all denoms from MaxWithdraw.
 - [1690](https://github.com/umee-network/umee/pull/1690) Add MaxBorrow message type.
-- [1711](https://github.com/umee-network/umee/pull/1711) Add historic pricing information to leverage MarketSummary query
-- [1715](https://github.com/umee-network/umee/pull/1715) Reverted.
-- [1723](https://github.com/umee-network/umee/pull/1723) Compute borrow limits using the lower of either spot or historic price for each collateral token, and the higher of said prices for borrowed tokens. Remove extra spot/historic only fields in account summary.
+- [1711](https://github.com/umee-network/umee/pull/1711) Add historic pricing information to leverage MarketSummary query.
+- [1723](https://github.com/umee-network/umee/pull/1723) Compute borrow limits using the lower of either spot or historic price for each collateral token, and the higher of said prices for borrowed tokens. Remove extra spot/historic only fields in account summum.
+- [1694](https://github.com/umee-network/umee/pull/1694) Add new sdkutil package to enhance common Cosmos SDK functionality. Here, the `ZeroCoin` helper function.
 
 ## [v3.3.0](https://github.com/umee-network/umee/releases/tag/v3.3.0) - 2022-12-20
 

proto/umee/leverage/v1/leverage.proto

@@ -237,6 +237,8 @@ message Token {
   // borrow positions under both current and historic prices. The default value of
   // zero for this field causes current price to be used in those calculations
   // for the affected Token.
+  // The time span covered by the historic median will be:
+  //     oracle.Params.median_stamp_period * oracle.Params.historic_stamp_period * historic_medians.
   uint32 historic_medians = 19 [
     (gogoproto.moretags) = "yaml:\"historic_medians\""
   ];

proto/umee/leverage/v1/tx.proto

@@ -24,6 +24,7 @@ service Msg {
 
   // MaxWithdraw moves previously supplied tokens from the module back to the user balance in
   // exchange for burning uTokens. It automatically calculates the maximum valid amount to withdraw.
+  // Zero is returned if there is no more tokens can be withdrawn.
   rpc MaxWithdraw(MsgMaxWithdraw) returns (MsgMaxWithdrawResponse);
 
   // Collateralize enables selected uTokens as collateral, which moves them to the module.
@@ -37,6 +38,7 @@ service Msg {
   rpc Borrow(MsgBorrow) returns (MsgBorrowResponse);
 
   // MaxBorrow allows a user to borrow the maximum amount of tokens their collateral will allow.
+  // Zero is returned if there is no more can be borrowed.
   rpc MaxBorrow(MsgMaxBorrow) returns (MsgMaxBorrowResponse);
 
   // Repay allows a user to repay previously borrowed tokens and interest.

util/sdkutil/coin.go

@@ -0,0 +1,18 @@
+package sdkutil
+
+import (
+	sdk "github.com/cosmos/cosmos-sdk/types"
+)
+
+// ZeroCoin returns new coin with zero amount
+func ZeroCoin(denom string) sdk.Coin {
+	return sdk.NewInt64Coin(denom, 0)
+}
+
+// Normalize transform nil coins to empty list
+func NormalizeCoins(cs sdk.Coins) sdk.Coins {
+	if cs == nil {
+		return sdk.Coins{}
+	}
+	return cs
+}

x/leverage/keeper/keeper.go

@@ -11,6 +11,7 @@ import (
 	paramtypes "github.com/cosmos/cosmos-sdk/x/params/types"
 	"github.com/tendermint/tendermint/libs/log"
 
+	"github.com/umee-network/umee/v4/util/sdkutil"
 	"github.com/umee-network/umee/v4/x/leverage/types"
 )
 
@@ -215,7 +216,8 @@ func (k Keeper) Repay(ctx sdk.Context, borrowerAddr sdk.AccAddress, payment sdk.
 	// determine amount of selected denom currently owed
 	owed := k.GetBorrow(ctx, borrowerAddr, payment.Denom)
 	if owed.IsZero() {
-		return sdk.Coin{}, types.ErrDenomNotBorrowed.Wrap(payment.Denom)
+		// no need to repay - everything is all right
+		return sdkutil.ZeroCoin(payment.Denom), nil
 	}
 
 	// prevent overpaying

x/leverage/keeper/limits.go

@@ -9,11 +9,7 @@ import (
 // maxWithdraw calculates the maximum amount of uTokens an account can currently withdraw.
 // input denom should be a base token.
 func (k *Keeper) maxWithdraw(ctx sdk.Context, addr sdk.AccAddress, denom string) (sdk.Coin, error) {
-	if types.HasUTokenPrefix(denom) {
-		return sdk.Coin{}, types.ErrUToken
-	}
 	uDenom := types.ToUTokenDenom(denom)
-
 	availableTokens := sdk.NewCoin(denom, k.AvailableLiquidity(ctx, denom))
 	availableUTokens, err := k.ExchangeToken(ctx, availableTokens)
 	if err != nil {

x/leverage/keeper/msg_server.go

@@ -5,6 +5,7 @@ import (
 
 	sdk "github.com/cosmos/cosmos-sdk/types"
 
+	"github.com/umee-network/umee/v4/util/sdkutil"
 	"github.com/umee-network/umee/v4/x/leverage/types"
 )
 
@@ -98,14 +99,21 @@ func (s msgServer) MaxWithdraw(
 	if err != nil {
 		return nil, err
 	}
+	if types.HasUTokenPrefix(msg.Denom) {
+		return nil, types.ErrUToken
+	}
+	if _, err = s.keeper.GetTokenSettings(ctx, msg.Denom); err != nil {
+		return nil, err
+	}
 
 	uToken, err := s.keeper.maxWithdraw(ctx, supplierAddr, msg.Denom)
 	if err != nil {
 		return nil, err
 	}
 
 	if uToken.IsZero() {
-		return nil, types.ErrMaxWithdrawZero
+		zeroCoin := sdkutil.ZeroCoin(msg.Denom)
+		return &types.MsgMaxWithdrawResponse{Withdrawn: uToken, Received: zeroCoin}, nil
 	}
 
 	received, err := s.keeper.Withdraw(ctx, supplierAddr, uToken)
@@ -329,7 +337,7 @@ func (s msgServer) MaxBorrow(
 		return nil, err
 	}
 	if maxBorrow.IsZero() {
-		return nil, types.ErrMaxBorrowZero
+		return &types.MsgMaxBorrowResponse{Borrowed: sdkutil.ZeroCoin(msg.Denom)}, nil
 	}
 
 	if err := s.keeper.Borrow(ctx, borrowerAddr, maxBorrow); err != nil {
@@ -371,7 +379,6 @@ func (s msgServer) Repay(
 	msg *types.MsgRepay,
 ) (*types.MsgRepayResponse, error) {
 	ctx := sdk.UnwrapSDKContext(goCtx)
-
 	borrowerAddr, err := sdk.AccAddressFromBech32(msg.Borrower)
 	if err != nil {
 		return nil, err