params: add FromAny function

Creating RPC server parameters from any data can be useful. Refs. #2909.

pkg/services/rpcsrv/params/params.go

@@ -1,12 +1,29 @@
 package params
 
-import "fmt"
+import (
+	"encoding/json"
+	"fmt"
+)
 
 type (
 	// Params represents the JSON-RPC params.
 	Params []Param
 )
 
+// FromAny allows to create Params for a slice of abstract values (by
+// JSON-marshaling them).
+func FromAny(arr []interface{}) (Params, error) {
+	var res Params
+	for i := range arr {
+		b, err := json.Marshal(arr[i])
+		if err != nil {
+			return nil, fmt.Errorf("wrong parameter %d: %w", i, err)
+		}
+		res = append(res, Param{RawMessage: json.RawMessage(b)})
+	}
+	return res, nil
+}
+
 // Value returns the param struct for the given
 // index if it exists.
 func (p Params) Value(index int) *Param {

pkg/services/rpcsrv/params/params_test.go

@@ -0,0 +1,31 @@
+package params
+
+import (
+	"testing"
+
+	"github.com/nspcc-dev/neo-go/pkg/smartcontract"
+	"github.com/stretchr/testify/require"
+)
+
+func TestParamsFromAny(t *testing.T) {
+	str := "jajaja"
+
+	ps, err := FromAny([]interface{}{str, smartcontract.Parameter{Type: smartcontract.StringType, Value: str}})
+	require.NoError(t, err)
+	require.Equal(t, 2, len(ps))
+
+	resStr, err := ps[0].GetString()
+	require.NoError(t, err)
+	require.Equal(t, resStr, str)
+
+	resFP, err := ps[1].GetFuncParam()
+	require.NoError(t, err)
+	require.Equal(t, resFP.Type, smartcontract.StringType)
+	resStr, err = resFP.Value.GetString()
+	require.NoError(t, err)
+	require.Equal(t, resStr, str)
+
+	// Invalid item.
+	_, err = FromAny([]interface{}{smartcontract.Parameter{Type: smartcontract.IntegerType, Value: str}})
+	require.Error(t, err)
+}