Add datastore dumper tool.

service/datastore/dumper/dumper_example_test.go

+// Copyright 2016 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 dumper
+
+import (
+        "fmt"
+
+        "github.com/luci/gae/impl/memory"
+        "github.com/luci/gae/service/datastore"
+        "golang.org/x/net/context"
+)
+
+type ExampleModel struct {
+        Kind   string         `gae:"$kind,Example"`
+        ID     int64          `gae:"$id"`
+        Parent *datastore.Key `gae:"$parent"`
+
+        Vals      []string
+        Number    int64
+        HexNumber int64
+}
+
+func ExampleConfig_Query() {
+        c := context.Background()
+        c = memory.Use(c)
+
+        ds := datastore.Get(c)
+        root := ds.MakeKey("Parent", 1)
+        models := []*ExampleModel{
+                {ID: 1, Vals: []string{"hi", "there"}, Number: 10, HexNumber: 20},
+                {ID: 2, Vals: []string{"other"}, Number: 11, HexNumber: 21},
+                {ID: 1, Parent: root, Vals: []string{"child", "ent"}},
+                {Kind: "Other", ID: 1, Vals: []string{"other"}, Number: 11, HexNumber: 21},
+        }
+        if err := ds.Put(models); err != nil {
+                panic(err)
+        }
+        // indexes must be up-to-date here.
+        ds.Testable().CatchupIndexes()
+
+        _, err := Config{
+                PropFilters: PropFilterMap{
+                        {"Example", "HexNumber"}: func(p datastore.Property) string {
+                                return fmt.Sprintf("0x%04x", p.Value())
+                        },
+                },
+                KindFilters: KindFilterMap{
+                        "Other": func(key *datastore.Key, pm datastore.PropertyMap) string {
+                                return "I AM A BANANA"
+                        },
+                },
+        }.Query(c, nil)
+        if err != nil {
+                panic(err)
+        }
+
+        // Output:
+        // dev~app::/Example,1:
+        //   "HexNumber": [0x0014]
+        //   "Number": [PTInt(10)]
+        //   "Vals": [
+        //     PTString("hi"),
+        //     PTString("there")
+        //   ]
+        //
+        // dev~app::/Example,2:
+        //   "HexNumber": [0x0015]
+        //   "Number": [PTInt(11)]
+        //   "Vals": [PTString("other")]
+        //
+        // dev~app::/Other,1:
+        //   I AM A BANANA
+        //
+        // dev~app::/Parent,1/Example,1:
+        //   "HexNumber": [0x0000]
+        //   "Number": [PTInt(0)]
+        //   "Vals": [
+        //     PTString("child"),
+        //     PTString("ent")
+        //   ]
+}