feat: add message index event attribute to authz message execution (#12668)

## Description

It's impossible currently for operators or clients to understand what events emitted from messages executed via `MsgExec` correspond to exactly what messages. This PR adds a message index attribute to each event emitted by a message via `MsgExec`.

---

### 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...

- [ ] 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
- [ ] targeted the correct branch (see [PR Targeting](https://github.com/cosmos/cosmos-sdk/blob/main/CONTRIBUTING.md#pr-targeting))
- [ ] provided a link to the relevant issue or specification
- [ ] followed the guidelines for [building modules](https://github.com/cosmos/cosmos-sdk/blob/main/docs/building-modules)
- [ ] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/main/CONTRIBUTING.md#testing)
- [ ] added a changelog entry to `CHANGELOG.md`
- [ ] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [ ] updated the relevant documentation or specification
- [ ] 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...

- [ ] 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

@@ -47,6 +47,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### Improvements
 
+* [#12668](https://github.com/cosmos/cosmos-sdk/pull/12668) Add `authz_msg_index` event attribute to message events emitted when executing via `MsgExec` through `x/authz`.
 * [#12634](https://github.com/cosmos/cosmos-sdk/pull/12634) Move `sdk.Dec` to math package.
 * [#12596](https://github.com/cosmos/cosmos-sdk/pull/12596) Remove all imports of the non-existent gogo/protobuf v1.3.3 to ease downstream use and go workspaces. 
 * [#12589](https://github.com/cosmos/cosmos-sdk/pull/12589) Allow zero gas in simulation mode.

x/authz/keeper/keeper.go

@@ -2,10 +2,11 @@ package keeper
 
 import (
 	"fmt"
+	"strconv"
 	"time"
 
 	"github.com/gogo/protobuf/proto"
-
+	abci "github.com/tendermint/tendermint/abci/types"
 	"github.com/tendermint/tendermint/libs/log"
 
 	"github.com/cosmos/cosmos-sdk/baseapp"
@@ -84,14 +85,17 @@ func (k Keeper) update(ctx sdk.Context, grantee sdk.AccAddress, granter sdk.AccA
 func (k Keeper) DispatchActions(ctx sdk.Context, grantee sdk.AccAddress, msgs []sdk.Msg) ([][]byte, error) {
 	results := make([][]byte, len(msgs))
 	now := ctx.BlockTime()
+
 	for i, msg := range msgs {
 		signers := msg.GetSigners()
 		if len(signers) != 1 {
 			return nil, authz.ErrAuthorizationNumOfSigners
 		}
+
 		granter := signers[0]
 
-		// if granter != grantee then check authorization.Accept, otherwise we implicitly accept.
+		// If granter != grantee then check authorization.Accept, otherwise we
+		// implicitly accept.
 		if !granter.Equals(grantee) {
 			skey := grantStoreKey(grantee, granter, sdk.MsgTypeURL(msg))
 
@@ -113,6 +117,7 @@ func (k Keeper) DispatchActions(ctx sdk.Context, grantee sdk.AccAddress, msgs []
 			if err != nil {
 				return nil, err
 			}
+
 			if resp.Delete {
 				err = k.DeleteGrant(ctx, grantee, granter, sdk.MsgTypeURL(msg))
 			} else if resp.Updated != nil {
@@ -121,6 +126,7 @@ func (k Keeper) DispatchActions(ctx sdk.Context, grantee sdk.AccAddress, msgs []
 			if err != nil {
 				return nil, err
 			}
+
 			if !resp.Accept {
 				return nil, sdkerrors.ErrUnauthorized
 			}
@@ -135,14 +141,19 @@ func (k Keeper) DispatchActions(ctx sdk.Context, grantee sdk.AccAddress, msgs []
 		if err != nil {
 			return nil, sdkerrors.Wrapf(err, "failed to execute message; message %v", msg)
 		}
+
 		results[i] = msgResp.Data
 
 		// emit the events from the dispatched actions
 		events := msgResp.Events
 		sdkEvents := make([]sdk.Event, 0, len(events))
-		for i := 0; i < len(events); i++ {
-			sdkEvents = append(sdkEvents, sdk.Event(events[i]))
+		for _, event := range events {
+			e := event
+			e.Attributes = append(e.Attributes, abci.EventAttribute{Key: "authz_msg_index", Value: strconv.Itoa(i)})
+
+			sdkEvents = append(sdkEvents, sdk.Event(e))
 		}
+
 		ctx.EventManager().EmitEvents(sdkEvents)
 	}
 

x/authz/keeper/keeper_test.go

@@ -316,9 +316,12 @@ func (s *TestSuite) TestDispatchedEvents() {
 	result, err := s.authzKeeper.DispatchActions(s.ctx, granteeAddr, executeMsgs)
 	require.NoError(err)
 	require.NotNil(result)
+
 	events := s.ctx.EventManager().Events()
+
 	// get last 5 events (events that occur *after* the grant)
 	events = events[len(events)-5:]
+
 	requiredEvents := map[string]bool{
 		"coin_spent":    false,
 		"coin_received": false,

x/authz/keeper/msg_server.go

@@ -17,6 +17,7 @@ func (k Keeper) Grant(goCtx context.Context, msg *authz.MsgGrant) (*authz.MsgGra
 	if err != nil {
 		return nil, err
 	}
+
 	// create the account if it is not in account state
 	granteeAcc := k.authKeeper.GetAccount(ctx, grantee)
 	if granteeAcc == nil {
@@ -33,6 +34,7 @@ func (k Keeper) Grant(goCtx context.Context, msg *authz.MsgGrant) (*authz.MsgGra
 	if err != nil {
 		return nil, err
 	}
+
 	t := authorization.MsgTypeURL()
 	if k.router.HandlerByTypeURL(t) == nil {
 		return nil, sdkerrors.ErrInvalidType.Wrapf("%s doesn't exist.", t)
@@ -73,13 +75,16 @@ func (k Keeper) Exec(goCtx context.Context, msg *authz.MsgExec) (*authz.MsgExecR
 	if err != nil {
 		return nil, err
 	}
+
 	msgs, err := msg.GetMessages()
 	if err != nil {
 		return nil, err
 	}
+
 	results, err := k.DispatchActions(ctx, grantee, msgs)
 	if err != nil {
 		return nil, err
 	}
+
 	return &authz.MsgExecResponse{Results: results}, nil
 }