feat: add DenomOwners gRPC method for x/bank (#9533)

# Description Adds a new gRPC method, `DenomOwners`, to the `x/bank` module. This method queries for all account addresses that own a particular token denomination (paginated). _Naming subject to change based on reviews._ closes: #9393 --- ### 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... - [x] 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 - [x] targeted the correct branch (see [PR Targeting](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#pr-targeting)) - [x] provided a link to the relevant issue or specification - [x] followed the guidelines for [building modules](https://github.com/cosmos/cosmos-sdk/blob/master/docs/building-modules) - [x] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#testing) - [x] added a changelog entry to `CHANGELOG.md` - [x] included comments for [documenting Go code](https://blog.golang.org/godoc) - [x] updated the relevant documentation or specification - [x] 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... - [x] 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 - [x] confirmed all author checklist items have been addressed - [x] reviewed state machine logic - [x] reviewed API design and naming - [x] reviewed documentation is accurate - [x] reviewed tests and test coverage - [ ] manually tested (if applicable)
cosmos · Jun 28, 2021 · d8059ff · d8059ff
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -37,7 +37,12 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ## [Unreleased]
 
+### Features
+
+* [\#9533](https://github.com/cosmos/cosmos-sdk/pull/9533) Added a new gRPC method, `DenomOwners`, in `x/bank` to query for all account holders of a specific denomination.
+
 ### API Breaking Changes
+
 * (client/tx) [\#9421](https://github.com/cosmos/cosmos-sdk/pull/9421/) `BuildUnsignedTx`, `BuildSimTx`, `PrintUnsignedStdTx` functions are moved to
   the Tx Factory as methods.
 

diff --git a/docs/core/proto-docs.md b/docs/core/proto-docs.md
@@ -89,12 +89,15 @@
     - [GenesisState](#cosmos.bank.v1beta1.GenesisState)
 
 - [cosmos/bank/v1beta1/query.proto](#cosmos/bank/v1beta1/query.proto)
+    - [DenomOwner](#cosmos.bank.v1beta1.DenomOwner)
     - [QueryAllBalancesRequest](#cosmos.bank.v1beta1.QueryAllBalancesRequest)
     - [QueryAllBalancesResponse](#cosmos.bank.v1beta1.QueryAllBalancesResponse)
     - [QueryBalanceRequest](#cosmos.bank.v1beta1.QueryBalanceRequest)
     - [QueryBalanceResponse](#cosmos.bank.v1beta1.QueryBalanceResponse)
     - [QueryDenomMetadataRequest](#cosmos.bank.v1beta1.QueryDenomMetadataRequest)
     - [QueryDenomMetadataResponse](#cosmos.bank.v1beta1.QueryDenomMetadataResponse)
+    - [QueryDenomOwnersRequest](#cosmos.bank.v1beta1.QueryDenomOwnersRequest)
+    - [QueryDenomOwnersResponse](#cosmos.bank.v1beta1.QueryDenomOwnersResponse)
     - [QueryDenomsMetadataRequest](#cosmos.bank.v1beta1.QueryDenomsMetadataRequest)
     - [QueryDenomsMetadataResponse](#cosmos.bank.v1beta1.QueryDenomsMetadataResponse)
     - [QueryParamsRequest](#cosmos.bank.v1beta1.QueryParamsRequest)
@@ -1703,6 +1706,19 @@ GenesisState defines the bank module's genesis state.
 
 
 
+<a name="cosmos.bank.v1beta1.DenomOwner"></a>
+
+### DenomOwner
+
+DenomOwner defines structure representing an account that owns or holds a
+particular denominated token. It contains the account address and account
+balance of the denominated token.
+
+| Field | Type | Label | Description |
+| ----- | ---- | ----- | ----------- |
+| `address` | [string](#string) |  | address defines the address that owns a particular denomination. |
+| `balance` | [cosmos.base.v1beta1.Coin](#cosmos.base.v1beta1.Coin) |  | balance is the balance of the denominated coin for an account. |
+
 <a name="cosmos.bank.v1beta1.QueryAllBalancesRequest"></a>
 
 ### QueryAllBalancesRequest
@@ -1798,6 +1814,40 @@ method.
 
 
 
+<a name="cosmos.bank.v1beta1.QueryDenomOwnersRequest"></a>
+
+### QueryDenomOwnersRequest
+QueryDenomOwnersRequest defines the request type for the DenomOwners RPC query,
+which queries for a paginated set of all account holders of a particular
+denomination.
+
+
+| Field | Type | Label | Description |
+| ----- | ---- | ----- | ----------- |
+| `denom` | [string](#string) |  | denom defines the coin denomination to query all account holders for. |
+| `pagination` | [cosmos.base.query.v1beta1.PageRequest](#cosmos.base.query.v1beta1.PageRequest) |  | pagination defines an optional pagination for the request. |
+
+
+
+
+
+
+<a name="cosmos.bank.v1beta1.QueryDenomOwnersResponse"></a>
+
+### QueryDenomOwnersResponse
+QueryDenomOwnersResponse defines the RPC response of a DenomOwners RPC query.
+
+
+| Field | Type | Label | Description |
+| ----- | ---- | ----- | ----------- |
+| `denom_owners` | [DenomOwner](#cosmos.bank.v1beta1.DenomOwner) | repeated |  |
+| `pagination` | [cosmos.base.query.v1beta1.PageResponse](#cosmos.base.query.v1beta1.PageResponse) |  | pagination defines the pagination in the response. |
+
+
+
+
+
+
 <a name="cosmos.bank.v1beta1.QueryDenomsMetadataRequest"></a>
 
 ### QueryDenomsMetadataRequest
@@ -1938,6 +1988,7 @@ Query defines the gRPC querier service.
 | `Params` | [QueryParamsRequest](#cosmos.bank.v1beta1.QueryParamsRequest) | [QueryParamsResponse](#cosmos.bank.v1beta1.QueryParamsResponse) | Params queries the parameters of x/bank module. | GET|/cosmos/bank/v1beta1/params|
 | `DenomMetadata` | [QueryDenomMetadataRequest](#cosmos.bank.v1beta1.QueryDenomMetadataRequest) | [QueryDenomMetadataResponse](#cosmos.bank.v1beta1.QueryDenomMetadataResponse) | DenomsMetadata queries the client metadata of a given coin denomination. | GET|/cosmos/bank/v1beta1/denoms_metadata/{denom}|
 | `DenomsMetadata` | [QueryDenomsMetadataRequest](#cosmos.bank.v1beta1.QueryDenomsMetadataRequest) | [QueryDenomsMetadataResponse](#cosmos.bank.v1beta1.QueryDenomsMetadataResponse) | DenomsMetadata queries the client metadata for all registered coin denominations. | GET|/cosmos/bank/v1beta1/denoms_metadata|
+| `DenomOwners` | [QueryDenomOwnersRequest](#cosmos.bank.v1beta1.QueryDenomOwnersRequest) | [QueryDenomOwnersResponse](#cosmos.bank.v1beta1.QueryDenomOwnersResponse) | DenomOwners queries for all account addresses that own a particular token denomination. | GET|/cosmos/bank/v1beta1/denom_owners/{denom}|
 
  <!-- end services -->
 
@@ -8259,4 +8310,3 @@ still be used for delegating and for governance votes even while locked.
 | <a name="bool" /> bool |  | bool | boolean | boolean | bool | bool | boolean | TrueClass/FalseClass |
 | <a name="string" /> string | A string must always contain UTF-8 encoded or 7-bit ASCII text. | string | String | str/unicode | string | string | string | String (UTF-8) |
 | <a name="bytes" /> bytes | May contain any arbitrary sequence of bytes. | string | ByteString | str | []byte | ByteString | string | String (ASCII-8BIT) |
-
diff --git a/proto/cosmos/bank/v1beta1/query.proto b/proto/cosmos/bank/v1beta1/query.proto
@@ -41,10 +41,17 @@ service Query {
     option (google.api.http).get = "/cosmos/bank/v1beta1/denoms_metadata/{denom}";
   }
 
-  // DenomsMetadata queries the client metadata for all registered coin denominations.
+  // DenomsMetadata queries the client metadata for all registered coin
+  // denominations.
   rpc DenomsMetadata(QueryDenomsMetadataRequest) returns (QueryDenomsMetadataResponse) {
     option (google.api.http).get = "/cosmos/bank/v1beta1/denoms_metadata";
   }
+
+  // DenomOwners queries for all account addresses that own a particular token
+  // denomination.
+  rpc DenomOwners(QueryDenomOwnersRequest) returns (QueryDenomOwnersResponse) {
+    option (google.api.http).get = "/cosmos/bank/v1beta1/denom_owners/{denom}";
+  }
 }
 
 // QueryBalanceRequest is the request type for the Query/Balance RPC method.
@@ -157,3 +164,33 @@ message QueryDenomMetadataResponse {
   // metadata describes and provides all the client information for the requested token.
   Metadata metadata = 1 [(gogoproto.nullable) = false];
 }
+
+// QueryDenomOwnersRequest defines the request type for the DenomOwners RPC query,
+// which queries for a paginated set of all account holders of a particular
+// denomination.
+message QueryDenomOwnersRequest {
+  // denom defines the coin denomination to query all account holders for.
+  string denom = 1;
+
+  // pagination defines an optional pagination for the request.
+  cosmos.base.query.v1beta1.PageRequest pagination = 2;
+}
+
+// DenomOwner defines structure representing an account that owns or holds a
+// particular denominated token. It contains the account address and account
+// balance of the denominated token.
+message DenomOwner {
+  // address defines the address that owns a particular denomination.
+  string address = 1;
+
+  // balance is the balance of the denominated coin for an account.
+  cosmos.base.v1beta1.Coin balance = 2 [(gogoproto.nullable) = false];
+}
+
+// QueryDenomOwnersResponse defines the RPC response of a DenomOwners RPC query.
+message QueryDenomOwnersResponse {
+  repeated DenomOwner denom_owners = 1;
+
+  // pagination defines the pagination in the response.
+  cosmos.base.query.v1beta1.PageResponse pagination = 2;
+}
diff --git a/x/bank/keeper/grpc_query.go b/x/bank/keeper/grpc_query.go
@@ -164,3 +164,61 @@ func (k BaseKeeper) DenomMetadata(c context.Context, req *types.QueryDenomMetada
 		Metadata: metadata,
 	}, nil
 }
+
+func (k BaseKeeper) DenomOwners(
+	goCtx context.Context,
+	req *types.QueryDenomOwnersRequest,
+) (*types.QueryDenomOwnersResponse, error) {
+
+	if req == nil {
+		return nil, status.Errorf(codes.InvalidArgument, "empty request")
+	}
+
+	if req.Denom == "" {
+		return nil, status.Error(codes.InvalidArgument, "empty denom")
+	}
+
+	ctx := sdk.UnwrapSDKContext(goCtx)
+
+	store := ctx.KVStore(k.storeKey)
+	balancesStore := prefix.NewStore(store, types.BalancesPrefix)
+
+	var denomOwners []*types.DenomOwner
+	pageRes, err := query.FilteredPaginate(
+		balancesStore,
+		req.Pagination,
+		func(key []byte, value []byte, accumulate bool) (bool, error) {
+			var balance sdk.Coin
+			if err := k.cdc.Unmarshal(value, &balance); err != nil {
+				return false, err
+			}
+
+			if req.Denom != balance.Denom {
+				return false, nil
+			}
+
+			if accumulate {
+				address, err := types.AddressFromBalancesStore(key)
+				if err != nil {
+					return false, err
+				}
+
+				denomOwners = append(
+					denomOwners,
+					&types.DenomOwner{
+						Address: address.String(),
+						Balance: balance,
+					},
+				)
+			}
+
+			return true, nil
+		},
+	)
+
+	if err != nil {
+		return nil, status.Error(codes.Internal, err.Error())
+	}
+
+	return &types.QueryDenomOwnersResponse{DenomOwners: denomOwners, Pagination: pageRes}, nil
+}
diff --git a/x/bank/keeper/grpc_query_test.go b/x/bank/keeper/grpc_query_test.go
@@ -5,13 +5,12 @@ import (
 	"fmt"
 
 	"github.com/cosmos/cosmos-sdk/simapp"
-
-	minttypes "github.com/cosmos/cosmos-sdk/x/mint/types"
-
 	"github.com/cosmos/cosmos-sdk/testutil/testdata"
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	"github.com/cosmos/cosmos-sdk/types/query"
+	authtypes "github.com/cosmos/cosmos-sdk/x/auth/types"
 	"github.com/cosmos/cosmos-sdk/x/bank/types"
+	minttypes "github.com/cosmos/cosmos-sdk/x/mint/types"
 )
 
 func (suite *IntegrationTestSuite) TestQueryBalance() {
@@ -305,3 +304,92 @@ func (suite *IntegrationTestSuite) QueryDenomMetadataRequest() {
 		})
 	}
 }
+
+func (suite *IntegrationTestSuite) TestGRPCDenomOwners() {
+	ctx := suite.ctx
+
+	authKeeper, keeper := suite.initKeepersWithmAccPerms(make(map[string]bool))
+	suite.Require().NoError(keeper.MintCoins(ctx, minttypes.ModuleName, initCoins))
+
+	for i := 0; i < 10; i++ {
+		acc := authKeeper.NewAccountWithAddress(ctx, authtypes.NewModuleAddress(fmt.Sprintf("account-%d", i)))
+		authKeeper.SetAccount(ctx, acc)
+
+		bal := sdk.NewCoins(sdk.NewCoin(
+			sdk.DefaultBondDenom,
+			sdk.TokensFromConsensusPower(initialPower/10, sdk.DefaultPowerReduction),
+		))
+		suite.Require().NoError(keeper.SendCoinsFromModuleToAccount(ctx, minttypes.ModuleName, acc.GetAddress(), bal))
+	}
+
+	testCases := map[string]struct {
+		req      *types.QueryDenomOwnersRequest
+		expPass  bool
+		numAddrs int
+		hasNext  bool
+		total    uint64
+	}{
+		"empty request": {
+			req:     &types.QueryDenomOwnersRequest{},
+			expPass: false,
+		},
+		"invalid denom": {
+			req: &types.QueryDenomOwnersRequest{
+				Denom: "foo",
+			},
+			expPass:  true,
+			numAddrs: 0,
+			hasNext:  false,
+			total:    0,
+		},
+		"valid request - page 1": {
+			req: &types.QueryDenomOwnersRequest{
+				Denom: sdk.DefaultBondDenom,
+				Pagination: &query.PageRequest{
+					Limit:      6,
+					CountTotal: true,
+				},
+			},
+			expPass:  true,
+			numAddrs: 6,
+			hasNext:  true,
+			total:    10,
+		},
+		"valid request - page 2": {
+			req: &types.QueryDenomOwnersRequest{
+				Denom: sdk.DefaultBondDenom,
+				Pagination: &query.PageRequest{
+					Offset:     6,
+					Limit:      10,
+					CountTotal: true,
+				},
+			},
+			expPass:  true,
+			numAddrs: 4,
+			hasNext:  false,
+			total:    10,
+		},
+	}
+
+	for name, tc := range testCases {
+		suite.Run(name, func() {
+			resp, err := suite.queryClient.DenomOwners(gocontext.Background(), tc.req)
+			if tc.expPass {
+				suite.NoError(err)
+				suite.NotNil(resp)
+				suite.Len(resp.DenomOwners, tc.numAddrs)
+				suite.Equal(tc.total, resp.Pagination.Total)
+
+				if tc.hasNext {
+					suite.NotNil(resp.Pagination.NextKey)
+				} else {
+					suite.Nil(resp.Pagination.NextKey)
+				}
+			} else {
+				suite.Require().Error(err)
+			}
+		})
+	}
+
+	suite.Require().True(true)
+}