Revert "Refactor current GAE abstraction library to be free of the SDK*"

go/src/infra/gae/libs/gae/upstream_errors.go

Index: go/src/infra/gae/libs/gae/upstream_errors.go
diff --git a/go/src/infra/gae/libs/gae/upstream_errors.go b/go/src/infra/gae/libs/gae/upstream_errors.go
deleted file mode 100644
index f6ebad5538ae2b3dd14ae34b0f3f6766cb8a9cf5..0000000000000000000000000000000000000000
--- a/go/src/infra/gae/libs/gae/upstream_errors.go
+++ /dev/null
@@ -1,109 +0,0 @@
-// 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"
-
-	"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 ////////////////////////////////
-
-// 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 {
-				s = e.Error()
-			}
-			n++
-		}
-	}
-	switch n {
-	case 0:
-		return "(0 errors)"
-	case 1:
-		return s
-	case 2:
-		return s + " (and 1 other error)"
-	}
-	return fmt.Sprintf("%s (and %d other errors)", s, n-1)
-}
-
-// SingleError provides a simple way to uwrap a MultiError if you know that it
-// could only ever contain one element.
-//
-// If err is a MultiError, return its first element. Otherwise, return err.
-func SingleError(err error) error {
-	if me, ok := err.(MultiError); ok {
-		if len(me) == 0 {
-			return nil
-		}
-		return me[0]
-	}
-	return err
-}
-
-var (
-	multiErrorType = reflect.TypeOf(MultiError(nil))
-)
-
-// FixError will convert a backend-specific non-plain error type to the
-// corresponding gae wrapper type. This is intended to be used solely by
-// implementations (not user code). A correct implementation of the gae wrapper
-// should never return an SDK-specific error type if an alternate type appears
-// in this file.
-func FixError(err error) error {
-	if err != nil {
-		// we know that err already conforms to the error interface (or the caller's
-		// method wouldn't compile), so check to see if the error's underlying type
-		// looks like one of the special error types we implement.
-		v := reflect.ValueOf(err)
-		if v.Type().ConvertibleTo(multiErrorType) {
-			err = v.Convert(multiErrorType).Interface().(error)
-		}
-	}
-	return err
-}