Add support for registering custom reply parsers.

This commit extends the RegisterCustomCmd function to also accept a reply
parser which will be invoked for replies to the custom command via
ReadResultCmd.  This allows replies to custom commands to be returned a
concrete structs instead of map[string]interface{}.

ok @jcvernaleo, @jrick

jsoncmd.go

@@ -63,17 +63,26 @@ func NewRawCmd(id interface{}, method string, params []interface{}) (*RawCmd, er
 // RawCmdParser is a function to create a custom Cmd from a RawCmd.
 type RawCmdParser func(*RawCmd) (Cmd, error)
 
+// ReplyParser is a function a custom Cmd can use to unmarshal the results of a
+// reply into a concrete struct.
+type ReplyParser func(json.RawMessage) (interface{}, error)
+
 type cmd struct {
 	parser      RawCmdParser
+	replyParser ReplyParser
 	helpString  string
 }
 
 var customCmds = make(map[string]cmd)
 
-// RegisterCustomCmd registers a custom RawCmd parsing func for a
-// non-standard Bitcoin command.
-func RegisterCustomCmd(method string, parser RawCmdParser, helpString string) {
-	customCmds[method] = cmd{parser: parser, helpString: helpString}
+// RegisterCustomCmd registers a custom RawCmd parsing func, reply parsing func,
+// and help text for a non-standard Bitcoin command.
+func RegisterCustomCmd(method string, parser RawCmdParser, replyParser ReplyParser, helpString string) {
+	customCmds[method] = cmd{
+		parser:      parser,
+		replyParser: replyParser,
+		helpString:  helpString,
+	}
 }
 
 // ParseMarshaledCmd parses a raw command and unmarshals as a Cmd.

jsonresults.go

@@ -509,11 +509,22 @@ func ReadResultCmd(cmd string, message []byte) (Reply, error) {
 		"getnewaddress", "sendtoaddress", "createrawtransaction",
 		"sendrawtransaction", "getbestblockhash", "getrawchangeaddress":
 		err = json.Unmarshal(message, &result)
-	// For anything else put it in an interface.  All the data is still
-	// there, just a little less convenient to deal with.
 	default:
+		// None of the standard Bitcoin RPC methods matched.  Try
+		// registered custom command reply parsers.
+		if c, ok := customCmds[cmd]; ok && c.replyParser != nil {
+			var res interface{}
+			res, err = c.replyParser(objmap["result"])
+			if err == nil {
+				result.Result = res
+			}
+		} else {
+			// For anything else put it in an interface.  All the
+			// data is still there, just a little less convenient
+			// to deal with.
 			err = json.Unmarshal(message, &result)
 		}
+	}
 	if err != nil {
 		err = fmt.Errorf("Error unmarshalling json reply: %v", err)
 		return result, err

test_coverage.txt

@@ -436,12 +436,12 @@ github.com/conformal/btcjson/jsoncmd.go		 VerifyMessageCmd.UnmarshalJSON		 68.42
 github.com/conformal/btcjson/jsoncmd.go		 SignRawTransactionCmd.MarshalJSON	 66.67% (8/12)
 github.com/conformal/btcjson/jsoncmd.go		 NewLockUnspentCmd			 66.67% (4/6)
 github.com/conformal/btcjson/jsoncmd.go		 NewAddNodeCmd				 66.67% (2/3)
-github.com/conformal/btcjson/jsoncmd.go		 GetBlockCmd.MarshalJSON		 63.64% (7/11)
 github.com/conformal/btcjson/jsonfxns.go	 jsonRpcSend				 62.50% (10/16)
 github.com/conformal/btcjson/jsonapi.go		 rpcCommand				 61.54% (8/13)
+github.com/conformal/btcjson/jsoncmd.go		 GetBlockCmd.MarshalJSON		 60.00% (6/10)
 github.com/conformal/btcjson/jsoncmd.go		 GetTxOutCmd.UnmarshalJSON		 59.09% (13/22)
-github.com/conformal/btcjson/jsonresults.go	 ReadResultCmd				 58.73% (74/126)
 github.com/conformal/btcjson/jsoncmd.go		 LockUnspentCmd.UnmarshalJSON		 57.89% (11/19)
+github.com/conformal/btcjson/jsonresults.go	 ReadResultCmd				 57.25% (75/131)
 github.com/conformal/btcjson/jsonapi.go		 rpcRawCommand				 53.33% (8/15)
 github.com/conformal/btcjson/jsoncmd.go		 GetBlockCmd.UnmarshalJSON		 50.00% (12/24)
 github.com/conformal/btcjson/cmdhelp.go		 GetHelpString				 50.00% (3/6)
@@ -462,5 +462,5 @@ github.com/conformal/btcjson/jsoncmd.go		 unparsableCmd.Method			 0.00% (0/1)
 github.com/conformal/btcjson/jsonapi.go		 TlsRpcRawCommand			 0.00% (0/1)
 github.com/conformal/btcjson/jsonapi.go		 RpcRawCommand				 0.00% (0/1)
 github.com/conformal/btcjson/jsonresults.go	 Vin.IsCoinBase				 0.00% (0/1)
-github.com/conformal/btcjson			 --------------------------------------- 78.61% (2338/2974)
+github.com/conformal/btcjson			 --------------------------------------- 78.51% (2338/2978)