add simulate command

simapp/simd/cmd/root.go

@@ -270,6 +270,7 @@ func txCommand() *cobra.Command {
 		authcmd.GetEncodeCommand(),
 		authcmd.GetDecodeCommand(),
 		authcmd.GetAuxToFeeCommand(),
+		authcmd.GetSimulateCmd(),
 	)
 
 	return cmd

simapp/simd/cmd/root_v2.go

@@ -287,6 +287,7 @@ func txCommand() *cobra.Command {
 		authcmd.GetEncodeCommand(),
 		authcmd.GetDecodeCommand(),
 		authcmd.GetAuxToFeeCommand(),
+		authcmd.GetSimulateCmd(),
 	)
 
 	return cmd

x/auth/client/cli/tx_simulate.go

@@ -0,0 +1,107 @@
+package cli
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/spf13/cobra"
+
+	"github.com/cosmos/cosmos-sdk/client"
+	"github.com/cosmos/cosmos-sdk/client/flags"
+	"github.com/cosmos/cosmos-sdk/client/tx"
+	"github.com/cosmos/cosmos-sdk/version"
+	authclient "github.com/cosmos/cosmos-sdk/x/auth/client"
+)
+
+// GetSimulateCmd returns a command that simulates whether a transaction will be
+// successful.
+func GetSimulateCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "simulate /path/to/tx.json --from keyname",
+		Short: "Simulate the gas usage of a transaction",
+		Long: strings.TrimSpace(
+			fmt.Sprintf(`Simulate whether a transaction will be successful:
+
+- if successful, the simulation result is printed, which includes the gas
+  consumption, message response data, and events emitted;
+- if unsuccessful, the error message is printed.
+
+Example:
+$ %s query simulate tx.json --from keyname
+
+Where tx.json is a JSON-encoded unsigned transaction, typically generated by any
+transaction command with the --generate-only flag. It shoud look like:
+
+{
+  "body": {
+    "messages": [
+      {
+        "@type": "/cosmos.bank.v1beta1.MsgSend",
+        "from_address": "cosmos1...",
+        "to_address": "cosmos1...",
+        "amount": [
+          {
+            "denom": "utoken",
+            "amount": "12345"
+          }
+        ]
+      }
+    ],
+    "memo": "",
+    "timeout_height": "0",
+    "extension_options": [],
+    "non_critical_extension_options": []
+  },
+  "auth_info": {
+    "signer_infos": [],
+    "fee": {
+      "amount": [],
+      "gas_limit": "200000",
+      "payer": "",
+      "granter": ""
+    },
+    "tip": null
+  },
+  "signatures": []
+}
+
+The --from flag is mandatory.
+`,
+				version.AppName,
+			),
+		),
+		Args: cobra.ExactArgs(1),
+		RunE: func(cmd *cobra.Command, args []string) error {
+			clientCtx, err := client.GetClientTxContext(cmd)
+			if err != nil {
+				return err
+			}
+
+			txf, err := tx.NewFactoryCLI(clientCtx, cmd.Flags())
+			if err != nil {
+				return err
+			}
+
+			txf, err = txf.Prepare(clientCtx)
+			if err != nil {
+				return err
+			}
+
+			stdTx, err := authclient.ReadTxFromFile(clientCtx, args[0])
+			if err != nil {
+				return err
+			}
+
+			simRes, _, err := tx.CalculateGas(clientCtx, txf, stdTx.GetMsgs()...)
+			if err != nil {
+				return err
+			}
+
+			return clientCtx.PrintProto(simRes)
+		},
+	}
+
+	flags.AddTxFlagsToCmd(cmd)
+
+	return cmd
+}