example: add jsonencode using extension (#3142)

examples/jsonencode/example_test.go

@@ -0,0 +1,62 @@
+// Copyright 2019-present Facebook Inc. All rights reserved.
+// This source code is licensed under the Apache 2.0 license found
+// in the LICENSE file in the root directory of this source tree.
+
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log"
+
+	"entgo.io/ent/examples/jsonencode/ent"
+	_ "github.com/mattn/go-sqlite3"
+)
+
+func Example_JSONEncode() {
+	client, err := ent.Open("sqlite3", "file:ent?mode=memory&cache=shared&_fk=1")
+	if err != nil {
+		log.Fatalf("failed opening connection to sqlite: %v", err)
+	}
+	defer client.Close()
+	ctx := context.Background()
+	// Run the auto migration tool.
+	if err := client.Schema.Create(ctx); err != nil {
+		log.Fatalf("failed creating schema resources: %v", err)
+	}
+
+	a8m := client.User.Create().SetName("a8m").SetAge(10).SaveX(ctx)
+	buf, err := json.Marshal(a8m)
+	if err != nil {
+		log.Fatalf("failed marshaling user: %v", err)
+	}
+	fmt.Println(string(buf))
+
+	xabi := client.Pet.Create().SetName("xabi").SetAge(1).SetOwner(a8m).SaveX(ctx)
+	buf, err = json.Marshal(xabi)
+	if err != nil {
+		log.Fatalf("failed marshaling pet: %v", err)
+	}
+	fmt.Println(string(buf))
+
+	users := client.User.Query().WithPets().AllX(ctx)
+	buf, err = json.Marshal(users)
+	if err != nil {
+		log.Fatalf("failed marshaling users: %v", err)
+	}
+	fmt.Println(string(buf))
+
+	pets := client.Pet.Query().WithOwner().AllX(ctx)
+	buf, err = json.Marshal(pets)
+	if err != nil {
+		log.Fatalf("failed marshaling pets: %v", err)
+	}
+	fmt.Println(string(buf))
+
+	// Output:
+	// {"id":1,"age":10,"name":"a8m"}
+	// {"id":1,"age":1,"name":"xabi","owner_id":1}
+	// [{"id":1,"age":10,"name":"a8m","pets":[{"id":1,"age":1,"name":"xabi","owner_id":1}]}]
+	// [{"id":1,"age":1,"name":"xabi","owner_id":1,"owner":{"id":1,"age":10,"name":"a8m"}}]
+}