Refactor a bit.

upstream_errors.go

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// This file contains types and values which are mirrors/duplicates of the
-// upstream SDK errors. This exists so that users can depend solely on this
-// wrapper library without also needing to import the SDK.
-//
-// Format of the errors is Err<sub>Name, where <sub> is one of the 2/3-letter
-// All Caps subpackage codes (e.g. DS, TQ, MC, etc.). Name is the same as the
-// original SDK error.
-//
-// Note that this only replicates the 'named' errors (which a user might compare
-// for equality or observe by-type in their code like ErrDSNoSuchEntity). The
-// underlying implementations can (and do) return many more sorts of non-named
-// and custom errors.
-
 package gae
 
 import (
         "fmt"
         "reflect"
         "sync"
-
-        "google.golang.org/appengine/datastore"
-        "google.golang.org/appengine/memcache"
-        "google.golang.org/appengine/taskqueue"
 )
 
-// These are pass-through versions from the managed-VM SDK. All implementations
-// must return these (exact) errors (not just an error with the same text).
-var (
-        ErrDSInvalidEntityType     = datastore.ErrInvalidEntityType
-        ErrDSInvalidKey            = datastore.ErrInvalidKey
-        ErrDSNoSuchEntity          = datastore.ErrNoSuchEntity
-        ErrDSConcurrentTransaction = datastore.ErrConcurrentTransaction
-        ErrDSQueryDone             = datastore.Done
-
-        ErrMCCacheMiss   = memcache.ErrCacheMiss
-        ErrMCCASConflict = memcache.ErrCASConflict
-        ErrMCNoStats     = memcache.ErrNoStats
-        ErrMCNotStored   = memcache.ErrNotStored
-        ErrMCServerError = memcache.ErrServerError
-
-        ErrTQTaskAlreadyAdded = taskqueue.ErrTaskAlreadyAdded
-)
-
-/////////////////////////////// Supporting code ////////////////////////////////
-
-// ErrDSFieldMismatch is returned when a field is to be loaded into a different
-// type than the one it was stored from, or when a field is missing or
-// unexported in the destination struct.
-// StructType is the type of the struct pointed to by the destination argument
-// passed to Get or to Iterator.Next.
-type ErrDSFieldMismatch struct {
-        StructType reflect.Type
-        FieldName  string
-        Reason     string
-}
-
-func (e *ErrDSFieldMismatch) Error() string {
-        return fmt.Sprintf("gae: cannot load field %q into a %q: %s",
-                e.FieldName, e.StructType, e.Reason)
-}
-
 // MultiError is returned by batch operations when there are errors with
 // particular elements. Errors will be in a one-to-one correspondence with
 // the input elements; successful elements will have a nil entry.
 type MultiError []error
 
 func (m MultiError) Error() string {
         s, n := "", 0
         for _, e := range m {
                 if e != nil {
                         if n == 0 {
@@ skipping 78 matching lines @@
 
 // Get returns the MultiError, or nil, if no non-nil error was Assign'd.
 func (e *LazyMultiError) Get() error {
         e.Lock()
         defer e.Unlock()
         if e.me == nil {
                 return nil
         }
         return e.me
 }