Validate VSP configs on startup.

config.go

@@ -974,6 +974,25 @@ func loadConfig(ctx context.Context) (*config, []string, error) {
 		}
 	}
 
+	// If either VSP pubkey or URL are specified, validate VSP options.
+	if cfg.VSPOpts.PubKey != "" || cfg.VSPOpts.URL != "" {
+		if cfg.VSPOpts.PubKey == "" {
+			err := errors.New("vsp pubkey can not be null")
+			fmt.Fprintln(os.Stderr, err)
+			return loadConfigError(err)
+		}
+		if cfg.VSPOpts.URL == "" {
+			err := errors.New("vsp URL can not be null")
+			fmt.Fprintln(os.Stderr, err)
+			return loadConfigError(err)
+		}
+		if cfg.VSPOpts.MaxFee.Amount == 0 {
+			err := errors.New("vsp max fee must be greater than zero")
+			fmt.Fprintln(os.Stderr, err)
+			return loadConfigError(err)
+		}
+	}
+
 	// Expand environment variable and leading ~ for filepaths.
 	cfg.CAFile.Value = cleanAndExpandPath(cfg.CAFile.Value)
 	cfg.RPCCert.Value = cleanAndExpandPath(cfg.RPCCert.Value)

internal/rpc/jsonrpc/methods.go

@@ -3424,29 +3424,14 @@ func (s *Server) purchaseTicket(ctx context.Context, icmd interface{}) (interfac
 	}
 
 	var vspClient *vsp.Client
-	if s.cfg.VSPHost != "" || s.cfg.VSPPubKey != "" {
-		vspHost := s.cfg.VSPHost
-		vspPubKey := s.cfg.VSPPubKey
-		vspMaxFee := s.cfg.VSPMaxFee
-		if vspPubKey == "" {
-			return nil, rpcErrorf(dcrjson.ErrRPCInvalidParameter,
-				"vsp pubkey can not be null")
-		}
-		if vspHost == "" {
-			return nil, rpcErrorf(dcrjson.ErrRPCInvalidParameter,
-				"vsp host can not be null")
-		}
-		if vspMaxFee == 0 {
-			return nil, rpcErrorf(dcrjson.ErrRPCInvalidParameter,
-				"vsp max fee must be greater than zero")
-		}
+	if s.cfg.VSPHost != "" {
 		cfg := vsp.Config{
-			URL:    vspHost,
-			PubKey: vspPubKey,
+			URL:    s.cfg.VSPHost,
+			PubKey: s.cfg.VSPPubKey,
 			Dialer: s.cfg.Dial,
 			Wallet: w,
 			Policy: vsp.Policy{
-				MaxFee:     vspMaxFee,
+				MaxFee:     s.cfg.VSPMaxFee,
 				FeeAcct:    account,
 				ChangeAcct: changeAccount,
 			},