Refactor multiarg, split MGS/PLS.

service/datastore/pls.go

 // Copyright 2015 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package datastore
 
 import (
         "fmt"
         "reflect"
 )
@@ skipping 201 matching lines @@
 //     ID Name `gae:"$id"`
 //   }
 func GetPLS(obj interface{}) interface {
         PropertyLoadSaver
         MetaGetterSetter
 } {
         v := reflect.ValueOf(obj)
         if !v.IsValid() {
                 panic(fmt.Errorf("cannot GetPLS(%T): failed to reflect", obj))
         }
-        if v.Kind() != reflect.Ptr || v.Elem().Kind() != reflect.Struct {
-                panic(fmt.Errorf("cannot GetPLS(%T): not a pointer-to-struct", obj))
+        if v.IsNil() {
+                panic(fmt.Errorf("cannot GetPLS(%T): pointer is nil", obj))
         }
-        if v.IsNil() {
-                panic(fmt.Errorf("cannot GetPLS(%T): pointer-to-struct is nil", obj))
+
+        if v.Kind() == reflect.Ptr {
+                v = v.Elem()
+                if v.Kind() == reflect.Struct {
+                        s := structPLS{
+                                c: getCodec(v.Type()),
+                                o: v,
+                        }
+
+                        // If our object implements MetaGetterSetter, use this instead of the built-in
+                        // PLS MetaGetterSetter.
+                        if mgs, ok := obj.(MetaGetterSetter); ok {
+                                s.mgs = mgs
+                        }
+                        return &s
+                }
         }
-        v = v.Elem()
-        c := getCodec(v.Type())
-        return &structPLS{v, c}
+        panic(fmt.Errorf("cannot GetPLS(%T): not a pointer-to-struct", obj))
 }
 
 func getMGS(obj interface{}) MetaGetterSetter {
         if mgs, ok := obj.(MetaGetterSetter); ok {
                 return mgs
         }
         return GetPLS(obj)
 }
 
 func getCodec(structType reflect.Type) *structCodec {
         structCodecsMutex.RLock()
         c, ok := structCodecs[structType]
         structCodecsMutex.RUnlock()
         if !ok {
                 structCodecsMutex.Lock()
                 defer structCodecsMutex.Unlock()
                 c = getStructCodecLocked(structType)
         }
         if c.problem != nil {
                 panic(c.problem)
         }
         return c
 }