fix(api): improve API response error handling (#2043)

Signed-off-by: Pavel Boldyrev <627562+bpg@users.noreply.github.com>

proxmox/api/client.go

@@ -334,12 +334,23 @@ func validateResponseCode(res *http.Response) error {
 		errRes := &ErrorResponseBody{}
 
 		err := json.NewDecoder(res.Body).Decode(errRes)
-		if err == nil && errRes.Errors != nil {
+		if err == nil {
 			var errList []string
 
+			if errRes.Errors != nil {
 				for k, v := range *errRes.Errors {
 					errList = append(errList, fmt.Sprintf("%s: %s", k, strings.TrimRight(v, "\n\r")))
 				}
+			}
+
+			if errRes.Message != nil && *errRes.Message != "" {
+				split := slices.Compact(strings.Split(*errRes.Message, "\n"))
+				// skip empty lines and the first line, which is a duplicate of the HTTP status message
+				split = slices.DeleteFunc(split, func(s string) bool {
+					return len(s) == 0 || strings.HasPrefix(s, msg)
+				})
+				errList = append(errList, split...)
+			}
 
 			msg = fmt.Sprintf("%s (%s)", msg, strings.Join(errList, " - "))
 		}

proxmox/api/client_test.go

@@ -9,6 +9,7 @@ package api
 import (
 	"context"
 	"errors"
+	"io"
 	"net/http"
 	"reflect"
 	"strconv"
@@ -53,6 +54,7 @@ func TestClientDoRequest(t *testing.T) {
 	tests := []struct {
 		name    string
 		status  string
+		body    string
 		wantErr error
 	}{
 		{name: "no error", status: "200 OK", wantErr: nil},
@@ -62,6 +64,15 @@ func TestClientDoRequest(t *testing.T) {
 			Code:    500,
 			Message: "Internal Server Error",
 		}},
+		{
+			name:   "500 status with body",
+			status: "500 create sdn zone object failed: 400 Parameter verification failed.",
+			body:   `{"message":"create sdn zone object failed: 400 Parameter verification failed.\nipam: ipam-simple not existing\n","data":null}`,
+			wantErr: &HTTPError{
+				Code:    500,
+				Message: "create sdn zone object failed: 400 Parameter verification failed. (ipam: ipam-simple not existing)",
+			},
+		},
 	}
 
 	for _, tt := range tests {
@@ -77,7 +88,7 @@ func TestClientDoRequest(t *testing.T) {
 						return &http.Response{
 							Status:     tt.status,
 							StatusCode: sc,
-							Body:       nil,
+							Body:       io.NopCloser(strings.NewReader(tt.body)),
 						}
 					}),
 				},

proxmox/api/client_types.go

@@ -21,6 +21,7 @@ type MultiPartData struct {
 // ErrorResponseBody contains the body of an error response.
 type ErrorResponseBody struct {
 	Data    *string            `json:"data"`
+	Message *string            `json:"message"`
 	Errors  *map[string]string `json:"errors"`
 }