R4R: Implement Tx Decode in REST/CLI Clients

.pending/features/gaiacli/3872-Add-gaiacli-tx-

@@ -0,0 +1 @@
+#3872 Implement a command to decode txs via `gaiacli tx decode`

.pending/features/gaiarest/3872-Add-POST-txs-de

@@ -0,0 +1 @@
+#3872 Implement a RESTful endpoint to decode txs via `POST /txs/decode`

client/lcd/swagger-ui/swagger.yaml

@@ -323,6 +323,36 @@ paths:
           description: The tx was malformated
         500:
           description: Server internal error
+  /txs/decode:
+    post:
+      tags:
+        - Transactions
+      summary: Decode a transaction from the Amino wire format
+      description: Decode a transaction (signed or not) from base64-encoded Amino serialized bytes to JSON
+      consumes:
+        - application/json
+      produces:
+        - application/json
+      parameters:
+        - in: body
+          name: tx
+          description: The tx to decode
+          required: true
+          schema:
+            type: object
+            properties:
+              tx:
+                type: string
+                example: SvBiXe4KPqijYZoKFFHEzJ8c2HPAfv2EFUcIhx0yPagwEhTy0vPA+GGhCEslKXa4Af0uB+mfShoMCgVzdGFrZRIDMTAwEgQQwJoM
+      responses:
+        200:
+          description: The tx was successfully decoded
+          schema:
+            $ref: "#/definitions/StdTx"
+        400:
+          description: The tx was malformated
+        500:
+          description: Server internal error
   /bank/balances/{address}:
     get:
       summary: Get the account balances

x/auth/client/rest/decode.go

@@ -0,0 +1,102 @@
+package rest
+
+import (
+	"encoding/base64"
+	"io/ioutil"
+	"net/http"
+
+	"github.com/cosmos/cosmos-sdk/client"
+	"github.com/cosmos/cosmos-sdk/client/context"
+	"github.com/cosmos/cosmos-sdk/types/rest"
+	authtypes "github.com/cosmos/cosmos-sdk/x/auth/types"
+
+	"github.com/spf13/cobra"
+	amino "github.com/tendermint/go-amino"
+)
+
+type (
+	// DecodeReq defines a tx decoding request.
+	DecodeReq struct {
+		Tx string `json:"tx"`
+	}
+
+	// DecodeResp defines a tx decoding response.
+	DecodeResp authtypes.StdTx
+)
+
+// DecodeTxRequestHandlerFn returns the decode tx REST handler. In particular,
+// it takes base64-decoded bytes, decodes it from the Amino wire protocol,
+// and responds with a json-formatted transaction.
+func DecodeTxRequestHandlerFn(cliCtx context.CLIContext) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		var req DecodeReq
+
+		body, err := ioutil.ReadAll(r.Body)
+		if err != nil {
+			rest.WriteErrorResponse(w, http.StatusBadRequest, err.Error())
+			return
+		}
+
+		err = cliCtx.Codec.UnmarshalJSON(body, &req)
+		if err != nil {
+			rest.WriteErrorResponse(w, http.StatusBadRequest, err.Error())
+			return
+		}
+
+		txBytes, err := base64.StdEncoding.DecodeString(req.Tx)
+		if err != nil {
+			rest.WriteErrorResponse(w, http.StatusBadRequest, err.Error())
+			return
+		}
+
+		var stdTx authtypes.StdTx
+		err = cliCtx.Codec.UnmarshalBinaryLengthPrefixed(txBytes, &stdTx)
+		if err != nil {
+			rest.WriteErrorResponse(w, http.StatusBadRequest, err.Error())
+			return
+		}
+
+		response := DecodeResp(stdTx)
+		rest.PostProcessResponse(w, cliCtx, response)
+	}
+}
+
+// txDecodeRespStr implements a simple Stringer wrapper for a decoded tx.
+type txDecodeRespTx authtypes.StdTx
+
+func (tx txDecodeRespTx) String() string {
+	return tx.String()
+}
+
+// GetDecodeCommand returns the decode command to take Amino-serialized bytes and turn it into
+// a JSONified transaction
+func GetDecodeCommand(codec *amino.Codec) *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "decode [amino-byte-string]",
+		Short: "Decode an amino-encoded transaction string",
+		Args:  cobra.ExactArgs(1),
+		RunE: func(cmd *cobra.Command, args []string) (err error) {
+			cliCtx := context.NewCLIContext().WithCodec(codec)
+
+			txBytesBase64 := args[0]
+
+			txBytes, err := base64.StdEncoding.DecodeString(txBytesBase64)
+			if err != nil {
+				return err
+			}
+
+			var stdTx authtypes.StdTx
+			err = cliCtx.Codec.UnmarshalBinaryLengthPrefixed(txBytes, &stdTx)
+			if err != nil {
+				return err
+			}
+
+			response := txDecodeRespTx(stdTx)
+			_ = cliCtx.PrintOutput(response)
+
+			return nil
+		},
+	}
+
+	return client.PostCommands(cmd)[0]
+}

x/auth/client/rest/rest.go

@@ -19,4 +19,5 @@ func RegisterTxRoutes(cliCtx context.CLIContext, r *mux.Router) {
 	r.HandleFunc("/txs", QueryTxsByEventsRequestHandlerFn(cliCtx)).Methods("GET")
 	r.HandleFunc("/txs", BroadcastTxRequest(cliCtx)).Methods("POST")
 	r.HandleFunc("/txs/encode", EncodeTxRequestHandlerFn(cliCtx)).Methods("POST")
+	r.HandleFunc("/txs/decode", DecodeTxRequestHandlerFn(cliCtx)).Methods("POST")
 }

x/auth/client/utils/tx.go

@@ -154,7 +154,12 @@ func PrintUnsignedStdTx(txBldr authtypes.TxBuilder, cliCtx context.CLIContext, m
 		return err
 	}
 
-	json, err := cliCtx.Codec.MarshalJSON(stdTx)
+	var json []byte
+	if viper.GetBool(flags.FlagIndentResponse) {
+		json, err = cliCtx.Codec.MarshalJSONIndent(stdTx, "", "  ")
+	} else {
+		json, err = cliCtx.Codec.MarshalJSON(stdTx)
+	}
 	if err != nil {
 		return err
 	}