examples: make examples testable

examples/o2mrecur/example_test.go

@@ -0,0 +1,102 @@
+// 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"
+	"fmt"
+	"log"
+
+	"github.com/facebookincubator/ent/examples/o2mrecur/ent"
+	"github.com/facebookincubator/ent/examples/o2mrecur/ent/node"
+
+	_ "github.com/mattn/go-sqlite3"
+)
+
+func Example_O2MRecur() {
+	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)
+	}
+	if err := Do(ctx, client); err != nil {
+		log.Fatal(err)
+	}
+	// Output:
+	// Tree leafs [1 3 5]
+	// [1 3 5]
+	// Node(id=1, value=2)
+}
+
+func Do(ctx context.Context, client *ent.Client) error {
+	root, err := client.Node.
+		Create().
+		SetValue(2).
+		Save(ctx)
+	if err != nil {
+		return fmt.Errorf("creating the root: %v", err)
+	}
+
+	// Add additional nodes to the tree:
+	//
+	//       2
+	//     /   \
+	//    1     4
+	//        /   \
+	//       3     5
+	//
+
+	// Unlike `Create`, `CreateX` panics if an error occurs.
+	n1 := client.Node.
+		Create().
+		SetValue(1).
+		SetParent(root).
+		SaveX(ctx)
+	n4 := client.Node.
+		Create().
+		SetValue(4).
+		SetParent(root).
+		SaveX(ctx)
+	n3 := client.Node.
+		Create().
+		SetValue(3).
+		SetParent(n4).
+		SaveX(ctx)
+	n5 := client.Node.
+		Create().
+		SetValue(5).
+		SetParent(n4).
+		SaveX(ctx)
+
+	fmt.Println("Tree leafs", []int{n1.Value, n3.Value, n5.Value})
+	// Output: Tree leafs [1 3 5]
+
+	// Get all leafs (nodes without children).
+	// Unlike `Int`, `IntX` panics if an error occurs.
+	ints := client.Node.
+		Query().                             // All nodes.
+		Where(node.Not(node.HasChildren())). // Only leafs.
+		Order(ent.Asc(node.FieldValue)).     // Order by their `value` field.
+		GroupBy(node.FieldValue).            // Extract only the `value` field.
+		IntsX(ctx)
+	fmt.Println(ints)
+	// Output: [1 3 5]
+
+	// Get orphan nodes (nodes without parent).
+	// Unlike `Only`, `OnlyX` panics if an error occurs.
+	orphan := client.Node.
+		Query().
+		Where(node.Not(node.HasParent())).
+		OnlyX(ctx)
+	fmt.Println(orphan)
+	// Output: Node(id=1, value=2)
+
+	return nil
+}