Simulate transaction should return execution result

[fedekunze]

Summary

Return result and gasConsumed (or GasInfo) when using ctx.QueryWithData("/app/simulate", txBytes) instead of only gasConsumed.

Problem Definition

#5421 refactored error handling and query logic around tx simulation. In particular handleQueryApp in the "simulate" was changed to return the gas consumed from the simulation instead of the sdk.Result.

Thi change broke one of the Web3 RPC calls, eth_Call, which executes a call without performing a state transition (i.e just like SDK simulation).

Ethermint needs the sdk.Result from this execution in order to unmarshal the result Data.

Proposal

Update handle query app to return sdk.Result and GasInfo by introducing a new type SimulationResponse:

func handleQueryApp(app *BaseApp, path []string, req abci.RequestQuery) abci.ResponseQuery {
	if len(path) >= 2 {
		switch path[1] {
		case "simulate":
			txBytes := req.Data

			tx, err := app.txDecoder(txBytes)
			if err != nil {
				return sdkerrors.QueryResult(sdkerrors.Wrap(err, "failed to decode tx"))
			}

			gInfo, res, _ := app.Simulate(txBytes, tx)

			simRes := sdk.SimulationReponse{
				GasInfo: gInfo,
				Result: res,	
			}

			return abci.ResponseQuery{
				Codespace: sdkerrors.RootCodespace,
				Height:    req.Height,
				Value:     codec.Cdc.MustMarshalBinaryLengthPrefixed(simRes),
			}
...

cc: @austinabell @alexanderbez

For Admin Use

• Not duplicate issue
• Appropriate labels applied
• Appropriate contributors tagged
• Contributor assigned/self-assigned

[alexanderbez]

Be sure to update the logic in the tx builder that decodes this response.