rpcserver: add parity with bitcoind for validateaddress

Updated the rpcserver handler for validateaddress JSON-RPC command to
have parity with the bitcoind 0.20.0 interface.

The new fields included are - isscript, iswitness, witness_version, and
witness_program. The scriptPubKey field has been left out since it
requires wallet access.

This update has no impact on the rpcclient.ValidateAddress method,
which uses the btcjson.ValidateAddressWalletResult type for modelling
the response from bitcoind.

btcjson/chainsvrresults.go

@@ -671,9 +671,17 @@ type TxRawDecodeResult struct {
 
 // ValidateAddressChainResult models the data returned by the chain server
 // validateaddress command.
+//
+// Compared to the Bitcoin Core version, this struct lacks the scriptPubKey
+// field since it requires wallet access, which is outside the scope of btcd.
+// Ref: https://bitcoincore.org/en/doc/0.20.0/rpc/util/validateaddress/
 type ValidateAddressChainResult struct {
-	IsValid bool   `json:"isvalid"`
-	Address string `json:"address,omitempty"`
+	IsValid        bool    `json:"isvalid"`
+	Address        string  `json:"address,omitempty"`
+	IsScript       *bool   `json:"isscript,omitempty"`
+	IsWitness      *bool   `json:"iswitness,omitempty"`
+	WitnessVersion *int32  `json:"witness_version,omitempty"`
+	WitnessProgram *string `json:"witness_program,omitempty"`
 }
 
 // EstimateSmartFeeResult models the data returned buy the chain server

rpcserver.go

@@ -3493,6 +3493,37 @@ func handleValidateAddress(s *rpcServer, cmd interface{}, closeChan <-chan struc
 		return result, nil
 	}
 
+	switch addr := addr.(type) {
+	case *btcutil.AddressPubKeyHash:
+		result.IsScript = btcjson.Bool(false)
+		result.IsWitness = btcjson.Bool(false)
+
+	case *btcutil.AddressScriptHash:
+		result.IsScript = btcjson.Bool(true)
+		result.IsWitness = btcjson.Bool(false)
+
+	case *btcutil.AddressPubKey:
+		result.IsScript = btcjson.Bool(false)
+		result.IsWitness = btcjson.Bool(false)
+
+	case *btcutil.AddressWitnessPubKeyHash:
+		result.IsScript = btcjson.Bool(false)
+		result.IsWitness = btcjson.Bool(true)
+		result.WitnessVersion = btcjson.Int32(int32(addr.WitnessVersion()))
+		result.WitnessProgram = btcjson.String(hex.EncodeToString(addr.WitnessProgram()))
+
+	case *btcutil.AddressWitnessScriptHash:
+		result.IsScript = btcjson.Bool(true)
+		result.IsWitness = btcjson.Bool(true)
+		result.WitnessVersion = btcjson.Int32(int32(addr.WitnessVersion()))
+		result.WitnessProgram = btcjson.String(hex.EncodeToString(addr.WitnessProgram()))
+
+	default:
+		// Handle the case when a new Address is supported by btcutil, but none
+		// of the cases were matched in the switch block. The current behaviour
+		// is to do nothing, and only populate the Address and IsValid fields.
+	}
+
 	result.Address = addr.EncodeAddress()
 	result.IsValid = true
 

rpcserverhelp.go

@@ -575,8 +575,12 @@ var helpDescsEnUS = map[string]string{
 	"submitblock--result1":    "The reason the block was rejected",
 
 	// ValidateAddressResult help.
-	"validateaddresschainresult-isvalid": "Whether or not the address is valid",
-	"validateaddresschainresult-address": "The bitcoin address (only when isvalid is true)",
+	"validateaddresschainresult-isvalid":         "Whether or not the address is valid",
+	"validateaddresschainresult-address":         "The bitcoin address (only when isvalid is true)",
+	"validateaddresschainresult-isscript":        "If the key is a script",
+	"validateaddresschainresult-iswitness":       "If the address is a witness address",
+	"validateaddresschainresult-witness_version": "The version number of the witness program",
+	"validateaddresschainresult-witness_program": "The hex value of the witness program",
 
 	// ValidateAddressCmd help.
 	"validateaddress--synopsis": "Verify an address is valid.",