From 15314e46d58aa1c90fe8f96de10b60fe1adfc017 Mon Sep 17 00:00:00 2001
From: Youngtaek Yoon <noreply@yoon.anonaddy.me>
Date: Fri, 7 Apr 2023 16:17:10 +0900
Subject: [PATCH] fix: allow zero amount of coin in x/collection Query/Balance
 (#953)

* Allow zero amount of coin

* Update CHANGELOG.md

* Update the test
---
 CHANGELOG.md                           |  1 +
 x/collection/keeper/grpc_query.go      |  5 ++++-
 x/collection/keeper/grpc_query_test.go | 18 +++++++++++++++++-
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 966b9c28e2..22fe5b5f7d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -51,6 +51,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * (x/foundation) [\#922](https://github.com/line/lbm-sdk/pull/922) Propagate events in x/foundation through sdk.Results
 * (x/foundation) [\#946](https://github.com/line/lbm-sdk/pull/946) Fix broken x/foundation invariant on treasury
 * (x/foundation) [\#947](https://github.com/line/lbm-sdk/pull/947) Unpack proposals in x/foundation import-genesis
+* (x/collection) [\#953](https://github.com/line/lbm-sdk/pull/953) Allow zero amount of coin in x/collection Query/Balance
 
 ### Removed
 
diff --git a/x/collection/keeper/grpc_query.go b/x/collection/keeper/grpc_query.go
index 75d8f22de4..ec308776c5 100644
--- a/x/collection/keeper/grpc_query.go
+++ b/x/collection/keeper/grpc_query.go
@@ -51,7 +51,10 @@ func (s queryServer) Balance(c context.Context, req *collection.QueryBalanceRequ
 
 	ctx := sdk.UnwrapSDKContext(c)
 	balance := s.keeper.GetBalance(ctx, req.ContractId, addr, req.TokenId)
-	coin := collection.NewCoin(req.TokenId, balance)
+	coin := collection.Coin{
+		TokenId: req.TokenId,
+		Amount:  balance,
+	}
 
 	return &collection.QueryBalanceResponse{Balance: coin}, nil
 }
diff --git a/x/collection/keeper/grpc_query_test.go b/x/collection/keeper/grpc_query_test.go
index b7bf82913c..363abafa77 100644
--- a/x/collection/keeper/grpc_query_test.go
+++ b/x/collection/keeper/grpc_query_test.go
@@ -27,7 +27,23 @@ func (s *KeeperTestSuite) TestQueryBalance() {
 			tokenID:    tokenID,
 			valid:      true,
 			postTest: func(res *collection.QueryBalanceResponse) {
-				expected := collection.NewCoin(tokenID, s.balance)
+				expected := collection.Coin{
+					TokenId: tokenID,
+					Amount: s.balance,
+				}
+				s.Require().Equal(expected, res.Balance)
+			},
+		},
+		"valid request with zero amount": {
+			contractID: s.contractID,
+			address:    s.vendor,
+			tokenID:    "deadbeefdeadbeef",
+			valid:      true,
+			postTest: func(res *collection.QueryBalanceResponse) {
+				expected := collection.Coin{
+					TokenId: "deadbeefdeadbeef",
+					Amount: sdk.ZeroInt(),
+				}
 				s.Require().Equal(expected, res.Balance)
 			},
 		},