feat: add tx fee event (backport cosmos#9860) (cosmos#9887)

* feat: add tx fee event (cosmos#9860)

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## Description

Closes: cosmos#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
- [x] confirmed all CI checks have passed

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- [ ] 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)

(cherry picked from commit 1d07ea4)

# Conflicts:
#	CHANGELOG.md

* fix changelog conflict

* Add changelog entry

* Smaller diff

* Space

Co-authored-by: colin axnér <[email protected]>
Co-authored-by: Amaury M <[email protected]>

CHANGELOG.md

@@ -36,6 +36,12 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 # Changelog
 
+## [Unreleased]
+
+### 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`.
+
 ## [v0.43.0](https://github.com/cosmos/cosmos-sdk/releases/tag/v0.43.0) - 2021-08-10
 
 ### Features
@@ -364,7 +370,7 @@ Every module contains its own CHANGELOG.md. Please refer to the module you are i
 * [\#9720](https://github.com/cosmos/cosmos-sdk/pull/9720) Feegrant grant cli granter now accepts key name as well as address in general and accepts only address in --generate-only mode
 * [\#9766](https://github.com/cosmos/cosmos-sdk/pull/9766) Fix hardcoded ledger signing algorithm on `keys add` command.
 * [\#9793](https://github.com/cosmos/cosmos-sdk/pull/9793) Fixed ECDSA/secp256r1 transaction malleability.
-* (server) [#9704](https://github.com/cosmos/cosmos-sdk/pull/9704) Start GRPCWebServer in goroutine, avoid blocking other services from starting.
+* (server) [#9704](https://github.com/cosmos/cosmos-sdk/pull/9704) Start GRPCWebServer in goroutine, avoid blocking other services from starting.
 * (bank) [\#9687](https://github.com/cosmos/cosmos-sdk/issues/9687) fixes [\#9159](https://github.com/cosmos/cosmos-sdk/issues/9159). Added migration to prune balances with zero coins.
 
 

types/events.go

@@ -287,6 +287,7 @@ var (
 
 	AttributeKeyAccountSequence = "acc_seq"
 	AttributeKeySignature       = "signature"
+	AttributeKeyFee             = "fee"
 
 	EventTypeMessage = "message"
 

x/auth/ante/fee.go

@@ -137,15 +137,12 @@ func (dfd *DeductFeeDecorator) checkDeductFee(ctx context.Context, feeTx sdk.Fee
 		}
 	}
 
-	if err := dfd.accountKeeper.GetEnvironment().EventService.EventManager(ctx).EmitKV(
-		sdk.EventTypeTx,
-		event.NewAttribute(sdk.AttributeKeyFee, fee.String()),
-		event.NewAttribute(sdk.AttributeKeyFeePayer, sdk.AccAddress(deductFeesFrom).String()),
-	); err != nil {
-		return err
-	}
+	events := sdk.Events{sdk.NewEvent(sdk.EventTypeTx,
+		sdk.NewAttribute(sdk.AttributeKeyFee, feeTx.GetFee().String()),
+	)}
+	ctx.EventManager().EmitEvents(events)
 
-	return nil
+	return next(ctx, tx, simulate)
 }
 
 // DeductFees deducts fees from the given account.