Make status code and NGINX error codes on internalError publicly accessible (#489)

Author: arussellf5

Diff for: client/nginx.go

@@ -52,6 +52,15 @@ var (
 	ErrPlusVersionNotFound = errors.New("plus version not found in the input string")
 )
 
+// StatusError is an interface that defines our API with consumers of the plus client errors.
+// The error will return a http status code and an NGINX error code.
+type StatusError interface {
+	Status() int
+	Code() string
+}
+
+var _ StatusError = (*internalError)(nil)
+
 // NginxClient lets you access NGINX Plus API.
 type NginxClient struct {
 	httpClient  *http.Client
@@ -112,8 +121,18 @@ type apiError struct {
 }
 
 type internalError struct {
-	err string
-	apiError
+	err      string
+	apiError apiError
+}
+
+// Status returns the HTTP status code of the error.
+func (internalError *internalError) Status() int {
+	return internalError.apiError.Status
+}
+
+// Status returns the NGINX error code on the response.
+func (internalError *internalError) Code() string {
+	return internalError.apiError.Code
 }
 
 // Error allows internalError to match the Error interface.
@@ -1782,7 +1801,7 @@ func (client *NginxClient) GetStreamServerZones(ctx context.Context) (*StreamSer
 	if err != nil {
 		var ie *internalError
 		if errors.As(err, &ie) {
-			if ie.Code == pathNotFoundCode {
+			if ie.Code() == pathNotFoundCode {
 				return &zones, nil
 			}
 		}
@@ -1808,7 +1827,7 @@ func (client *NginxClient) GetStreamUpstreams(ctx context.Context) (*StreamUpstr
 	if err != nil {
 		var ie *internalError
 		if errors.As(err, &ie) {
-			if ie.Code == pathNotFoundCode {
+			if ie.Code() == pathNotFoundCode {
 				return &upstreams, nil
 			}
 		}
@@ -1824,7 +1843,7 @@ func (client *NginxClient) GetStreamZoneSync(ctx context.Context) (*StreamZoneSy
 	if err != nil {
 		var ie *internalError
 		if errors.As(err, &ie) {
-			if ie.Code == pathNotFoundCode {
+			if ie.Code() == pathNotFoundCode {
 				return nil, nil
 			}
 		}
@@ -2137,7 +2156,7 @@ func (client *NginxClient) GetStreamConnectionsLimit(ctx context.Context) (*Stre
 	if err != nil {
 		var ie *internalError
 		if errors.As(err, &ie) {
-			if ie.Code == pathNotFoundCode {
+			if ie.Code() == pathNotFoundCode {
 				return &limitConns, nil
 			}
 		}

Diff for: client/nginx_test.go

@@ -3,6 +3,7 @@ package client
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"net/http"
 	"net/http/httptest"
 	"reflect"
@@ -1438,6 +1439,70 @@ func TestUpdateStreamServers(t *testing.T) {
 	}
 }
 
+func TestInternalError(t *testing.T) {
+	t.Parallel()
+
+	// mimic a user-defined interface type
+	type TestStatusError interface {
+		Status() int
+		Code() string
+	}
+
+	//nolint // ignore golangci-lint err113 sugggestion to create package level static error
+	anotherErr := errors.New("another error")
+
+	notFoundErr := &internalError{
+		err: "not found error",
+		apiError: apiError{
+			Text:   "not found error",
+			Status: http.StatusNotFound,
+			Code:   "not found code",
+		},
+	}
+
+	testcases := map[string]struct {
+		inputErr       error
+		expectedCode   string
+		expectedStatus int
+	}{
+		"simple not found": {
+			inputErr:       notFoundErr,
+			expectedStatus: http.StatusNotFound,
+			expectedCode:   "not found code",
+		},
+		"not found joined with another error": {
+			inputErr:       errors.Join(notFoundErr, anotherErr),
+			expectedStatus: http.StatusNotFound,
+			expectedCode:   "not found code",
+		},
+		"not found wrapped with another error": {
+			inputErr:       notFoundErr.Wrap("some error"),
+			expectedStatus: http.StatusNotFound,
+			expectedCode:   "not found code",
+		},
+	}
+
+	for name, tc := range testcases {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			var se TestStatusError
+			ok := errors.As(tc.inputErr, &se)
+			if !ok {
+				t.Fatalf("could not cast error %v as StatusError", tc.inputErr)
+			}
+
+			if se.Status() != tc.expectedStatus {
+				t.Fatalf("expected status %d, got status %d", tc.expectedStatus, se.Status())
+			}
+
+			if se.Code() != tc.expectedCode {
+				t.Fatalf("expected code %s, got code %s", tc.expectedCode, se.Code())
+			}
+		})
+	}
+}
+
 type response struct {
 	servers    interface{}
 	statusCode int