fix(stf,server/v2/cometbft): fix default events + improve codec handling

server/v2/cometbft/grpc.go

@@ -256,13 +256,19 @@ func (t txServer[T]) Simulate(ctx context.Context, req *txtypes.SimulateRequest)
 		msgResponses = append(msgResponses, anyMsg)
 	}
 
+	event, err := intoABCIEvents(txResult.Events, map[string]struct{}{}, false)
+	if err != nil {
+		return nil, status.Errorf(codes.Unknown, "failed to convert events: %v", err)
+	}
+
 	return &txtypes.SimulateResponse{
 		GasInfo: &sdk.GasInfo{
 			GasUsed:   txResult.GasUsed,
 			GasWanted: txResult.GasWanted,
 		},
 		Result: &sdk.Result{
 			MsgResponses: msgResponses,
+			Events:       event,
 		},
 	}, nil
 }

server/v2/stf/stf.go

@@ -2,8 +2,10 @@ package stf
 
 import (
 	"context"
+	"encoding/json"
 	"errors"
 	"fmt"
+	"strings"
 
 	appmodulev2 "cosmossdk.io/core/appmodule/v2"
 	corecontext "cosmossdk.io/core/context"
@@ -358,12 +360,53 @@ func (s STF[T]) runTxMsgs(
 			e.EventIndex = int32(j + 1)
 			events = append(events, e)
 		}
+
+		// add message event
+		events = append(events, createMessageEvent(msg, int32(i+1), int32(len(execCtx.events)+1)))
 	}
 
 	consumed := execCtx.meter.Limit() - execCtx.meter.Remaining()
 	return msgResps, consumed, events, nil
 }
 
+// Create a message event, with two kv: action, the type url of the message
+// and module, the module of the message.
+func createMessageEvent(msg transaction.Msg, msgIndex, eventIndex int32) event.Event {
+	// Assumes that module name is the second element of the msg type URL
+	// e.g. "cosmos.bank.v1beta1.MsgSend" => "bank"
+	// It returns an empty string if the input is not a valid type URL
+	getModuleNameFromTypeURL := func(input string) string {
+		moduleName := strings.Split(input, ".")
+		if len(moduleName) > 1 {
+			return moduleName[1]
+		}
+
+		return ""
+	}
+
+	return event.Event{
+		MsgIndex:   msgIndex,
+		EventIndex: eventIndex,
+		Type:       "message",
+		Attributes: func() ([]appdata.EventAttribute, error) {
+			typeURL := msgTypeURL(msg)
+			return []appdata.EventAttribute{
+				{Key: "message.action", Value: "/" + typeURL},
+				{Key: "message.module", Value: getModuleNameFromTypeURL(typeURL)},
+			}, nil
+		},
+		Data: func() (json.RawMessage, error) {
+			typeURL := msgTypeURL(msg)
+			attrs := []appdata.EventAttribute{
+				{Key: "message.action", Value: "/" + typeURL},
+				{Key: "message.module", Value: getModuleNameFromTypeURL(typeURL)},
+			}
+
+			return json.Marshal(attrs)
+		},
+	}
+}
+
 // preBlock executes the pre block logic.
 func (s STF[T]) preBlock(
 	ctx *executionContext,

tests/systemtests/tx_test.go

@@ -122,7 +122,7 @@ func TestSimulateTx_GRPC(t *testing.T) {
 				require.NoError(t, err)
 				// Check the result and gas used are correct.
 				//
-				// The 12 events are:
+				// The 10 events are:
 				// - Sending Fee to the pool: coin_spent, coin_received and transfer
 				// - tx.* events: tx.fee, tx.acc_seq, tx.signature
 				// - Sending Amount to recipient: coin_spent, coin_received and transfer