What causes "expected object for struct, got %T" in semaphoreui/semaphore?

Inspect the backup JSON at the reported field and change the value to a JSON object ({...}) matching the struct shape.

expected object for struct, got %T

Error message

expected object for struct, got %T

What it means

unmarshalValueWithBackupTags (services/project/backup_marshal.go:198) handles struct destinations by requiring the corresponding JSON data to be a map[string]any (a JSON object). If the data is any other type - string, number, array, bool, or null - it returns "expected object for struct, got %T" before recursing into unmarshalStructWithBackupTags.

Solutions

Inspect the backup JSON at the reported field and change the value to a JSON object ({...}) matching the struct shape.
Verify you pass the correct top-level object to Unmarshal - if the backup root is an array, unmarshal into a slice target instead.
Make the Go field a slice ([]T) if the data is legitimately an array.
Re-export the backup with the current tool version so the JSON shapes match the struct definitions.

Example fix

// before (backup.json)
"inventory": ["inv1", "inv2"]   // array, target is struct
// after
"inventory": {"name": "inv1", "project_id": 1}

Defensive patterns

Strategy: type-guard

Validate before calling

var raw any
json.Unmarshal(backupData, &raw)
if _, ok := raw.(map[string]any); !ok {
    return errors.New("backup root must be a JSON object")
}

Type guard

func isJSONObject(v any) bool { _, ok := v.(map[string]any); return ok }

Try / catch

if err := project.Unmarshal(data, &target); err != nil {
    if strings.Contains(err.Error(), "expected object for struct") {
        return fmt.Errorf("backup JSON shape does not match struct: %w", err)
    }
    return err
}

Prevention

Ensure struct fields map to JSON objects, not arrays or scalars.
Unmarshal JSON arrays into slice targets, not structs.
Validate backup JSON structure against the entity schema before restoring.

When it happens

Trigger: During backup restore, a struct-kind field is matched with backup JSON whose value is not an object - e.g. the field maps to a JSON string/array/number, or the whole payload passed to Unmarshal is not a JSON object while the target is a struct.

Common situations: Backup file where a nested entity was serialized as an array or scalar instead of an object; passing the wrong data element to Unmarshal (e.g. a JSON array of objects into a struct target); hand-edited or corrupted backup JSON; version drift changing a field from object to array.

Related errors

AI-assisted analysis of semaphoreui/semaphore@1774ccb71a (2026-09-07). Data as JSON: /api/errors/5808cdb701f0483f. Report an issue: GitHub.

Appendix: source

Thrown at services/project/backup_marshal.go:198

	}
}

func unmarshalValueWithBackupTags(data any, v reflect.Value) error {
	// Handle pointers
	if v.Kind() == reflect.Ptr {
		// Initialize pointer if it's nil
		if v.IsNil() {
			v.Set(reflect.New(v.Type().Elem()))
		}
		return unmarshalValueWithBackupTags(data, v.Elem())
	}

	// Handle structs
	if v.Kind() == reflect.Struct {
		// Data should be a map
		m, ok := data.(map[string]any)
		if !ok {
			return fmt.Errorf("expected object for struct, got %T", data)
		}
		return unmarshalStructWithBackupTags(m, v)
	}

	// Handle slices and arrays
	if v.Kind() == reflect.Slice {
		dataSlice, ok := data.([]any)
		if !ok {
			return fmt.Errorf("expected array for slice, got %T", data)
		}
		slice := reflect.MakeSlice(v.Type(), len(dataSlice), len(dataSlice))
		for i := 0; i < len(dataSlice); i++ {
			elem := slice.Index(i)
			if err := unmarshalValueWithBackupTags(dataSlice[i], elem); err != nil {
				return err
			}
		}
		v.Set(slice)

View on GitHub (pinned to 1774ccb71a)