Fix #66.

impl/memory/datastore_test.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 memory
 
 import (
         "errors"
         "fmt"
         "testing"
@@ skipping 713 matching lines @@
                 m := Model{ID: 1}
                 So(ds.Put(c, &m), ShouldBeNil)
 
                 // Reset to something non zero to ensure zero is fetched.
                 m.Time = time.Now().UTC()
                 So(ds.Get(c, &m), ShouldBeNil)
                 So(m.Time.IsZero(), ShouldBeTrue)
         })
 }
 
+// High level test for ancestor queries where the parent and child have
+// identical fields. There was a bug where it would accidentally load the parent
+// entity when attempt to query for the child.
+func TestAncestorChildFieldQuery(t *testing.T) {

[dnj, 2016/11/20 16:44:25]

Can this test be folded up into one of the "datastore_intex_*test" test cases?
Feels weird having it sit top-level.

+        ctx := Use(context.Background())
+        testable := ds.GetTestable(ctx)
+        testable.Consistent(true)
+        testable.AutoIndex(true)
+
+        type Parent struct {
+                _       int64 `gae:"$id,1"`
+                Created time.Time
+        }
+        p := Parent{}
+        if err := ds.Put(ctx, &p); err != nil {
+                t.Fatal(err)
+        }
+        // If you comment out the .Order part below, the test succeeds

[dnj, 2016/11/20 16:44:25]

This comment can be removed.

+        q := ds.NewQuery("notParent").Ancestor(ds.KeyForObj(ctx, &p)).Order("-Created")
+        if val, err := ds.Count(ctx, q); err != nil {
+                t.Fatal(err)
+        } else if val != 0 {
+                t.Fatalf("val: %d != 0", val)
+        }
+}
+
 func TestNewDatastore(t *testing.T) {
         t.Parallel()
 
         Convey("Can get and use a NewDatastore", t, func() {
                 c := UseWithAppID(context.Background(), "dev~aid")
                 c = infoS.MustNamespace(c, "ns")
 
                 dsInst := NewDatastore(c, infoS.Raw(c))
                 c = ds.SetRaw(c, dsInst)
 
@@ skipping 64 matching lines @@
                         // Add "foos" to a new namespace, then confirm that it gets indexed.
                         So(ds.Put(infoS.MustNamespace(ctx, "qux"), foos), ShouldBeNil)
                         ds.GetTestable(ctx).CatchupIndexes()
 
                         results = nil
                         So(ds.GetAll(infoS.MustNamespace(ctx, "qux"), q, &results), ShouldBeNil)
                         So(len(results), ShouldEqual, 2)
                 })
         })
 }