feat: add tx fee event (#9860)

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## Description

Closes: #9857 

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---

### Author Checklist

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- [x] included the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [x] 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
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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)

CHANGELOG.md

@@ -39,6 +39,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### Features
 
+* [\#9860](https://github.com/cosmos/cosmos-sdk/pull/9860) Emit transaction fee in ante handler fee decorator. The event type is `tx` and the attribute is `fee`.
 * [\#9776](https://github.com/cosmos/cosmos-sdk/pull/9776) Add flag `staking-bond-denom` to specify the staking bond denomination value when initializing a new chain.
 * [\#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.
 * (bank) [\#9618](https://github.com/cosmos/cosmos-sdk/pull/9618) Update bank.Metadata: add URI and URIHash attributes.

types/events.go

@@ -227,6 +227,7 @@ var (
 
 	AttributeKeyAccountSequence = "acc_seq"
 	AttributeKeySignature       = "signature"
+	AttributeKeyFee             = "fee"
 
 	EventTypeMessage = "message"
 

x/auth/ante/fee.go

@@ -117,6 +117,11 @@ func (dfd DeductFeeDecorator) AnteHandle(ctx sdk.Context, tx sdk.Tx, simulate bo
 		}
 	}
 
+	events := sdk.Events{sdk.NewEvent(sdk.EventTypeTx,
+		sdk.NewAttribute(sdk.AttributeKeyFee, feeTx.GetFee().String()),
+	)}
+	ctx.EventManager().EmitEvents(events)
+
 	return next(ctx, tx, simulate)
 }
 

x/auth/client/testutil/suite.go

@@ -428,6 +428,76 @@ func (s *IntegrationTestSuite) TestCLIQueryTxCmdByEvents() {
 	}
 }
 
+func (s *IntegrationTestSuite) TestCLIQueryTxsCmdByEvents() {
+	val := s.network.Validators[0]
+
+	account2, err := val.ClientCtx.Keyring.Key("newAccount2")
+	s.Require().NoError(err)
+
+	sendTokens := sdk.NewInt64Coin(s.cfg.BondDenom, 10)
+
+	// Send coins.
+	out, err := s.createBankMsg(
+		val, account2.GetAddress(),
+		sdk.NewCoins(sendTokens),
+	)
+	s.Require().NoError(err)
+	var txRes sdk.TxResponse
+	s.Require().NoError(val.ClientCtx.Codec.UnmarshalJSON(out.Bytes(), &txRes))
+	s.Require().NoError(s.network.WaitForNextBlock())
+
+	// Query the tx by hash to get the inner tx.
+	out, err = clitestutil.ExecTestCLICmd(val.ClientCtx, authcli.QueryTxCmd(), []string{txRes.TxHash, fmt.Sprintf("--%s=json", tmcli.OutputFlag)})
+	s.Require().NoError(err)
+	s.Require().NoError(val.ClientCtx.Codec.UnmarshalJSON(out.Bytes(), &txRes))
+
+	testCases := []struct {
+		name        string
+		args        []string
+		expectEmpty bool
+	}{
+		{
+			"fee event happy case",
+			[]string{
+				fmt.Sprintf("--events=tx.fee=%s",
+					sdk.NewCoins(sdk.NewCoin(s.cfg.BondDenom, sdk.NewInt(10))).String()),
+				fmt.Sprintf("--%s=json", tmcli.OutputFlag),
+			},
+			false,
+		},
+		{
+			"no matching fee event",
+			[]string{
+				fmt.Sprintf("--events=tx.fee=%s",
+					sdk.NewCoins(sdk.NewCoin(s.cfg.BondDenom, sdk.NewInt(0))).String()),
+				fmt.Sprintf("--%s=json", tmcli.OutputFlag),
+			},
+			true,
+		},
+	}
+
+	for _, tc := range testCases {
+		tc := tc
+		s.Run(tc.name, func() {
+			cmd := authcli.QueryTxsByEventsCmd()
+			clientCtx := val.ClientCtx
+
+			out, err := clitestutil.ExecTestCLICmd(clientCtx, cmd, tc.args)
+			s.Require().NoError(err)
+
+			var result sdk.SearchTxsResult
+			s.Require().NoError(val.ClientCtx.Codec.UnmarshalJSON(out.Bytes(), &result))
+
+			if tc.expectEmpty {
+				s.Require().Equal(0, len(result.Txs))
+			} else {
+				s.Require().NotEqual(0, len(result.Txs))
+				s.Require().NotNil(result.Txs[0])
+			}
+		})
+	}
+}
+
 func (s *IntegrationTestSuite) TestCLISendGenerateSignAndBroadcast() {
 	val1 := s.network.Validators[0]