feat(dingo): introduce injection tracing

dingo.go

@@ -15,16 +15,24 @@ const (
 	DEFAULT
 )
 
-var ErrInvalidInjectReceiver = errors.New("usage of 'Inject' method with struct receiver is not allowed")
-var traceCircular []circularTraceEntry
-var errPointersToInterface = errors.New(" Do not use pointers to interface.")
+var (
+	ErrInvalidInjectReceiver = errors.New("usage of 'Inject' method with struct receiver is not allowed")
+	errPointersToInterface   = errors.New(" Do not use pointers to interface.")
+
+	traceCircular    []circularTraceEntry
+	injectionTracing = false
+)
 
 // EnableCircularTracing activates dingo's trace feature to find circular dependencies
 // this is super expensive (memory wise), so it should only be used for debugging purposes
 func EnableCircularTracing() {
 	traceCircular = make([]circularTraceEntry, 0)
 }
 
+func EnableInjectionTracing() {
+	injectionTracing = true
+}
+
 type (
 	// Injector defines bindings and multibindings
 	// it is possible to have a parent-injector, which can be asked if no resolution is available
@@ -386,6 +394,14 @@ func (injector *Injector) createInstanceOfAnnotatedType(t reflect.Type, annotati
 		return n, injector.requestInjection(n.Interface(), subCircularTrace)
 	}
 
+	if injectionTracing {
+		if t.PkgPath() == "" || t.Name() == "" {
+			log.Println("INJECTING: " + t.String())
+		} else {
+			log.Println("INJECTING: " + t.PkgPath() + "#" + t.Name() + " \"" + annotation + "\"")
+		}
+	}
+
 	n := reflect.New(t)
 	return n, injector.requestInjection(n.Interface(), nil)
 }
@@ -742,11 +758,20 @@ func (injector *Injector) requestInjection(object interface{}, circularTrace []c
 						}
 					}
 					if field.Kind() != reflect.Ptr && field.Kind() != reflect.Interface && instance.Kind() == reflect.Ptr {
+						if injectionTracing {
+							log.Println("SETTING FIELD: \"" + currentFieldName + "\" of type: \"" + ctype.Field(fieldIndex).Type.String() + "\"")
+						}
+
 						field.Set(instance.Elem())
 					} else {
 						if field.Kind() == reflect.Ptr && field.Type().Kind() == reflect.Ptr && field.Type().Elem().Kind() == reflect.Interface {
 							return wrapErr(fmt.Errorf("field %#v is pointer to interface. %w", currentFieldName, errPointersToInterface))
 						}
+
+						if injectionTracing {
+							log.Println("SETTING FIELD: \"" + currentFieldName + "\" of type: \"" + ctype.Field(fieldIndex).Type.String() + "\"")
+						}
+
 						field.Set(instance)
 					}
 				}