Allow metadata fields to be PropertyConverters for symmetry.

service/datastore/pls_test.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.
 
 // adapted from github.com/golang/appengine/datastore
 
 package datastore
 
 import (
         "bytes"
@@ skipping 623 matching lines @@
                 if kind != "KindOverride" {
                         i.customKind = kind
                 } else {
                         i.customKind = ""
                 }
                 return nil
         }
         return ErrMetaFieldUnset
 }
 
+type EmbeddedID struct {
+        Thing string
+        Val   int
+}
+
+var _ PropertyConverter = (*EmbeddedID)(nil)
+
+func (e *EmbeddedID) ToProperty() (ret Property, err error) {
+        return mpNI(fmt.Sprintf("%s|%d", e.Thing, e.Val)), nil
+}
+
+func (e *EmbeddedID) FromProperty(val Property) error {
+        if val.Type() != PTString {
+                return fmt.Errorf("gotta have a string")
+        }
+        toks := strings.SplitN(val.Value().(string), "|", 2)
+        if len(toks) != 2 {
+                return fmt.Errorf("gotta have two parts")
+        }
+        v, err := strconv.Atoi(toks[1])
+        if err != nil {
+                return err
+        }
+
+        e.Thing = toks[0]
+        e.Val = v
+        return nil
+}
+
+type IDEmbedder struct {
+        EmbeddedID `gae:"$id"`
+}
+
 type Simple struct{}
 
 type testCase struct {
         desc       string
         src        interface{}
         want       interface{}
         plsErr     string
         saveErr    string
         plsLoadErr string
         loadErr    string
@@ skipping 1249 matching lines @@
                                 "$kind": {mpNI("wut")},
                         })
 
                         props, err := GetPLS(ko).Save(true)
                         So(err, ShouldBeNil)
                         So(props, ShouldResemble, PropertyMap{
                                 "$id":   {mpNI(20)},
                                 "$kind": {mpNI("wut")},
                         })
                 })
+
+                Convey("Embeddable Metadata structs", func() {
+                        ide := &IDEmbedder{EmbeddedID{"hello", 10}}
+                        pls := GetPLS(ide)
+                        val, err := pls.GetMeta("id")
+                        So(err, ShouldBeNil)
+                        So(val, ShouldEqual, "hello|10")
+
+                        So(pls.SetMeta("id", "sup|1337"), ShouldBeNil)
+                        So(ide.EmbeddedID, ShouldResemble, EmbeddedID{"sup", 1337})
+
+                        So(pls.GetAllMeta(), ShouldResembleV, PropertyMap{
+                                "$id":   {mpNI("sup|1337")},
+                                "$kind": {mpNI("IDEmbedder")},
+                        })
+                })
         })
 }