add test for response error and refactor

Author: Aryan Tikarya

handler.go

@@ -102,17 +102,17 @@ func (e *respError) val(errors *Errors) reflect.Value {
 
 			if len(e.Meta) > 0 && v.Type().Implements(marshalableRT) {
 				_ = v.Interface().(marshalable).UnmarshalJSON(e.Meta)
-			} else {
-				msgField := v.Elem().FieldByName("Message")
-				if msgField.IsValid() && msgField.CanSet() && msgField.Kind() == reflect.String {
-					msgField.SetString(e.Message)
-				}
+			}
+
+			msgField := v.Elem().FieldByName("Message")
+			if msgField.IsValid() && msgField.CanSet() && msgField.Kind() == reflect.String {
+				msgField.SetString(e.Message)
+			}
 
-				if v.Type().Implements(errorsRT) {
-					dataField := v.Elem().FieldByName("Data")
-					if dataField.IsValid() && dataField.CanSet() {
-						dataField.Set(reflect.ValueOf(e.Data))
-					}
+			if v.Type().Implements(errorsRT) {
+				dataField := v.Elem().FieldByName("Data")
+				if dataField.IsValid() && dataField.CanSet() {
+					dataField.Set(reflect.ValueOf(e.Data))
 				}
 			}
 

resp_error_test.go

@@ -0,0 +1,224 @@
+package jsonrpc
+
+import (
+	"encoding/json"
+	"reflect"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+// Define the error types
+type SimpleError struct {
+	Message string
+}
+
+func (e *SimpleError) Error() string {
+	return e.Message
+}
+
+type DataError struct {
+	Message string
+	Data    interface{}
+}
+
+func (e *DataError) Error() string {
+	return e.Message
+}
+
+func (e *DataError) ErrorData() interface{} {
+	return e.Data
+}
+
+type MetaError struct {
+	Message string
+	Details string
+}
+
+func (e *MetaError) Error() string {
+	return e.Message
+}
+
+func (e *MetaError) MarshalJSON() ([]byte, error) {
+	return json.Marshal(struct {
+		Details string `json:"details"`
+	}{
+		Details: e.Details,
+	})
+}
+
+func (e *MetaError) UnmarshalJSON(data []byte) error {
+	var temp struct {
+		Details string `json:"details"`
+	}
+	if err := json.Unmarshal(data, &temp); err != nil {
+		return err
+	}
+	e.Details = temp.Details
+	return nil
+}
+
+type ComplexError struct {
+	Message string
+	Data    interface{}
+	Details string
+}
+
+func (e *ComplexError) Error() string {
+	return e.Message
+}
+
+func (e *ComplexError) ErrorData() interface{} {
+	return e.Data
+}
+
+func (e *ComplexError) MarshalJSON() ([]byte, error) {
+	return json.Marshal(struct {
+		Message string      `json:"message"`
+		Details string      `json:"details"`
+		Data    interface{} `json:"data"`
+	}{
+		Details: e.Details,
+		Message: e.Message,
+		Data:    e.Data,
+	})
+}
+
+func (e *ComplexError) UnmarshalJSON(data []byte) error {
+	var temp struct {
+		Message string      `json:"message"`
+		Details string      `json:"details"`
+		Data    interface{} `json:"data"`
+	}
+	if err := json.Unmarshal(data, &temp); err != nil {
+		return err
+	}
+	e.Details = temp.Details
+	e.Message = temp.Message
+	e.Data = temp.Data
+	return nil
+}
+
+func TestRespErrorVal(t *testing.T) {
+	// Initialize the Errors struct and register error types
+	errorsMap := NewErrors()
+	errorsMap.Register(1001, new(*SimpleError))
+	errorsMap.Register(1002, new(*DataError))
+	errorsMap.Register(1003, new(*MetaError))
+	errorsMap.Register(1004, new(*ComplexError))
+
+	// Define test cases
+	testCases := []struct {
+		name         string
+		respError    *respError
+		expectedType reflect.Type
+		verify       func(err error) error
+	}{
+		{
+			name: "SimpleError",
+			respError: &respError{
+				Code:    1001,
+				Message: "simple error occurred",
+			},
+			expectedType: reflect.TypeOf(&SimpleError{}),
+			verify: func(err error) error {
+				require.IsType(t, &SimpleError{}, err)
+				require.Equal(t, "simple error occurred", err.Error())
+				return nil
+			},
+		},
+		{
+			name: "DataError",
+			respError: &respError{
+				Code:    1002,
+				Message: "data error occurred",
+				Data:    "additional data",
+			},
+			expectedType: reflect.TypeOf(&DataError{}),
+			verify: func(err error) error {
+				require.IsType(t, &DataError{}, err)
+				require.Equal(t, "data error occurred", err.Error())
+				require.Equal(t, "additional data", err.(*DataError).ErrorData())
+				return nil
+			},
+		},
+		{
+			name: "MetaError",
+			respError: &respError{
+				Code:    1003,
+				Message: "meta error occurred",
+				Meta: func() json.RawMessage {
+					me := &MetaError{
+						Details: "meta details",
+					}
+					metaData, _ := me.MarshalJSON()
+					return metaData
+				}(),
+			},
+			expectedType: reflect.TypeOf(&MetaError{}),
+			verify: func(err error) error {
+				require.IsType(t, &MetaError{}, err)
+				require.Equal(t, "meta error occurred", err.Error())
+				// details will also be included in the error message since it implements the marshable interface
+				require.Equal(t, "meta details", err.(*MetaError).Details)
+				return nil
+			},
+		},
+		{
+			name: "ComplexError",
+			respError: &respError{
+				Code:    1004,
+				Message: "complex error occurred",
+				Data:    "complex data",
+				Meta: func() json.RawMessage {
+					ce := &ComplexError{
+						Details: "complex details",
+					}
+					metaData, _ := ce.MarshalJSON()
+					return metaData
+				}(),
+			},
+			expectedType: reflect.TypeOf(&ComplexError{}),
+			verify: func(err error) error {
+				require.IsType(t, &ComplexError{}, err)
+				require.Equal(t, "complex error occurred", err.Error())
+				require.Equal(t, "complex data", err.(*ComplexError).ErrorData())
+				require.Equal(t, "complex details", err.(*ComplexError).Details)
+				return nil
+			},
+		},
+		{
+			name: "UnregisteredError",
+			respError: &respError{
+				Code:    9999,
+				Message: "unregistered error occurred",
+				Data:    "some data",
+			},
+			expectedType: reflect.TypeOf(&respError{}),
+			verify: func(err error) error {
+				require.IsType(t, &respError{}, err)
+				require.Equal(t, "unregistered error occurred", err.Error())
+				require.Equal(t, "some data", err.(*respError).ErrorData())
+				return nil
+			},
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			errValue := tc.respError.val(&errorsMap)
+			errInterface := errValue.Interface()
+			err, ok := errInterface.(error)
+			if !ok {
+				t.Fatalf("returned value does not implement error interface")
+			}
+
+			if reflect.TypeOf(err) != tc.expectedType {
+				t.Errorf("expected error type %v, got %v", tc.expectedType, reflect.TypeOf(err))
+			}
+
+			err = tc.verify(err)
+			require.NoError(t, err, "failed to verify error")
+		})
+	}
+}