fix error marshalling issues

events/message.go

@@ -18,7 +18,9 @@ package events
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
+	"strings"
 	"time"
 
 	"go.opentelemetry.io/otel"
@@ -303,11 +305,73 @@ func (r AuthRelationshipRelation) Validate() error {
 	return err
 }
 
+// Errors contains one or more errors and handles marshalling the errors.
+// See [Errors.MarshalJSON] and [Errors.UnmarshalJSON] for details on how marshalling is done.
+type Errors []error
+
+// MarshalJSON encodes a string of arrays with each errors Error string.
+// Entries which are nil are skipped.
+// If no non nil errors are provided, null is returned.
+func (e Errors) MarshalJSON() ([]byte, error) {
+	errs := make([]string, 0, len(e))
+
+	for _, err := range e {
+		if err != nil {
+			errs = append(errs, err.Error())
+		}
+	}
+
+	if len(errs) == 0 {
+		return []byte("null"), nil
+	}
+
+	return json.Marshal(errs)
+}
+
+// UnmarshalJSON converts a list of string errors into new errors.
+// All errors unmarshalled are new errors and cannot be compared directly to another error.
+// Errors should be checked using string comparison.
+func (e *Errors) UnmarshalJSON(b []byte) error {
+	var errs []string
+
+	if err := json.Unmarshal(b, &errs); err != nil {
+		return err
+	}
+
+	if len(errs) == 0 {
+		*e = nil
+
+		return nil
+	}
+
+	*e = make(Errors, len(errs))
+
+	for i, err := range errs {
+		(*e)[i] = errors.New(err) //nolint:goerr113 // errors are dynamically returned
+	}
+
+	return nil
+}
+
+// Error returns each error on a new line.
+// Nil error are not included.
+func (e Errors) Error() string {
+	errs := make([]string, 0, len(e))
+
+	for _, err := range e {
+		if err != nil {
+			errs = append(errs, err.Error())
+		}
+	}
+
+	return strings.Join(errs, "\n")
+}
+
 // AuthRelationshipResponse contains the data structure expected to be received from an AuthRelationshipRequest
 // message to write or delete an auth relationship from PermissionsAPI
 type AuthRelationshipResponse struct {
 	// Errors contains any errors, if empty the request was successful
-	Errors []error `json:"errors"`
+	Errors Errors `json:"errors"`
 	// TraceContext is a map of values used for OpenTelemetry context propagation.
 	TraceContext map[string]string `json:"traceContext"`
 	// TraceID is the ID of the trace for this event

events/nats_test.go

@@ -2,7 +2,9 @@ package events_test
 
 import (
 	"context"
+	"encoding/json"
 	"errors"
+	"os"
 	"testing"
 	"time"
 
@@ -193,6 +195,134 @@ func TestNATSRequestReply(t *testing.T) {
 
 	close(respGot)
 }
+func TestNATSRequestReplyMarshalling(t *testing.T) {
+	testCases := []struct {
+		name           string
+		input          events.AuthRelationshipResponse
+		expectDecoded  map[string]any
+		expectResponse events.AuthRelationshipResponse
+	}{
+		{
+			"no error",
+			events.AuthRelationshipResponse{
+				TraceID:      "some-id",
+				TraceContext: map[string]string{},
+			},
+			map[string]any{
+				"errors":       nil,
+				"spanID":       "",
+				"traceContext": map[string]any{},
+				"traceID":      "some-id",
+			},
+			events.AuthRelationshipResponse{
+				TraceID:      "some-id",
+				TraceContext: map[string]string{},
+			},
+		},
+		{
+			"with errors",
+			events.AuthRelationshipResponse{
+				TraceID:      "some-id",
+				TraceContext: map[string]string{},
+				Errors: []error{
+					os.ErrInvalid,
+				},
+			},
+			map[string]any{
+				"errors": []any{
+					os.ErrInvalid.Error(),
+				},
+				"spanID":       "",
+				"traceContext": map[string]any{},
+				"traceID":      "some-id",
+			},
+			events.AuthRelationshipResponse{
+				TraceID:      "some-id",
+				TraceContext: map[string]string{},
+				Errors: []error{
+					errors.New(os.ErrInvalid.Error()), //nolint:goerr113 // ensure equals same error with text
+				},
+			},
+		},
+		{
+			"nil errors skipped",
+			events.AuthRelationshipResponse{
+				TraceID:      "some-id",
+				TraceContext: map[string]string{},
+				Errors: []error{
+					os.ErrInvalid,
+					nil,
+					os.ErrExist,
+					nil,
+				},
+			},
+			map[string]any{
+				"errors": []any{
+					os.ErrInvalid.Error(),
+					os.ErrExist.Error(),
+				},
+				"spanID":       "",
+				"traceContext": map[string]any{},
+				"traceID":      "some-id",
+			},
+			events.AuthRelationshipResponse{
+				TraceID:      "some-id",
+				TraceContext: map[string]string{},
+				Errors: []error{
+					errors.New(os.ErrInvalid.Error()), //nolint:goerr113 // ensure equals same error with text
+					errors.New(os.ErrExist.Error()),   //nolint:goerr113 // ensure equals same error with text
+				},
+			},
+		},
+		{
+			"all nil errors skipped",
+			events.AuthRelationshipResponse{
+				TraceID:      "some-id",
+				TraceContext: map[string]string{},
+				Errors: []error{
+					nil,
+					nil,
+				},
+			},
+			map[string]any{
+				"errors":       nil,
+				"spanID":       "",
+				"traceContext": map[string]any{},
+				"traceID":      "some-id",
+			},
+			events.AuthRelationshipResponse{
+				TraceID:      "some-id",
+				TraceContext: map[string]string{},
+				Errors:       nil,
+			},
+		},
+	}
+
+	for _, tc := range testCases {
+		tc := tc
+
+		t.Run(tc.name, func(t *testing.T) {
+			encoded, err := json.Marshal(tc.input)
+			require.NoError(t, err, "unexpected error marshalling input")
+
+			decoded := map[string]any{}
+
+			err = json.Unmarshal(encoded, &decoded)
+			require.NoError(t, err, "unexpected error unmarshalling encoded input into map")
+
+			assert.Equal(t, tc.expectDecoded, decoded, "unexpected encoded response")
+
+			var response events.AuthRelationshipResponse
+
+			err = json.Unmarshal(encoded, &response)
+			require.NoError(t, err, "unexpected error unmarshalling encoded input into response")
+
+			assert.Equal(t, tc.expectResponse, response, "unexpected response")
+
+			assert.Equal(t, len(tc.expectResponse.Errors), len(response.Errors), "unexpected response error count")
+		})
+	}
+}
 
 func getSingleMessage[T any](messages <-chan events.Message[T], timeout time.Duration) (events.Message[T], error) {
 	select {