Interface update, per-method Contexts.

filter/txnBuf/ds_txn.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 txnBuf
 
 import (
         ds "github.com/luci/gae/service/datastore"
         "github.com/luci/luci-go/common/errors"
         "golang.org/x/net/context"
@@ skipping 98 matching lines @@
 }
 
 func (d *dsTxnBuf) RunInTransaction(cb func(context.Context) error, opts *ds.TransactionOptions) error {
         if !d.haveLock {
                 d.state.Lock()
                 defer d.state.Unlock()
         }
         return withTxnBuf(d.ic, cb, opts)
 }
 
-func (d *dsTxnBuf) Testable() ds.Testable {
-        return d.state.parentDS.Testable()
+func (d *dsTxnBuf) CurrentTransaction() ds.Transaction { return d.state.parentDS.CurrentTransaction() }

[dnj, 2016/09/01 15:25:39]

Perhaps in the future, we can synthesize transaction objects for the nested
transactions here. ATM we're just returning the underlying DS's transaction. I
was torn between implementing this right now and waiting until stronger support
for "WithTransaction" is implemented to do this, since it's not very useful
without that. 

[iannucci, 2016/09/16 01:01:13]

hm good point. Yes I think waiting on this is a good call, but please document
it in the mean time (in doc.go)

[dnj, 2016/09/16 05:44:42]

Done.

+
+func (d *dsTxnBuf) WithTransaction(t ds.Transaction) context.Context {
+        return d.state.parentDS.WithTransaction(nil)

[iannucci, 2016/09/16 01:01:13]

doesn't this need to remove transaction stuff from the context.Context as well?
Basically what the GetNoTxn function used to do?

[dnj, 2016/09/16 05:44:42]

Done.

 }
+
+func (d *dsTxnBuf) GetTestable() ds.Testable {
+        return nil

[dnj, 2016/09/01 15:25:39]

oops, I'll make sure this returns parentDS's Testable in next patch set, don't
know how this got nil'd.

[dnj, 2016/09/16 05:44:42]

Done.

+}