Unexpected bahaviour when mutating 1-to-1 relations

Users Dgraph
7

This test reproduces the error I mentioned and the behaviour @Joschka described in his post:

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"testing"

	"github.com/dgraph-io/dgo/v2"
	"github.com/dgraph-io/dgo/v2/protos/api"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	"google.golang.org/grpc"
)

func Test_it_replaces_uid_predicates(t *testing.T) {
	conn, err := grpc.Dial("localhost:9080", grpc.WithInsecure())
	if err != nil {
		t.Fatalf("conntect: %v", err)
	}

	dg := dgo.NewDgraphClient(api.NewDgraphClient(conn))
	defer dg.Alter(context.Background(), &api.Operation{DropAll: true})

	err = dg.Alter(context.Background(), &api.Operation{
		Schema: `
type Node {
  name: string
  child: uid
}

name: string .
child: uid .
`,
	})
	require.NoError(t, err)

	type Node struct {
		UID  string `json:"uid"`
		Type string `json:"dgraph.type"`

		Name  string `json:"name"`
		Child *Node  `json:"child"`
	}

	in := Node{
		UID:  "_:parent",
		Type: "Node",
		Name: "parent",
		Child: &Node{
			UID:  "_:child",
			Type: "Node",
			Name: "child",
		},
	}

	js, err := json.Marshal(in)
	require.NoError(t, err)

	res, err := dg.NewTxn().Mutate(context.Background(), &api.Mutation{CommitNow: true, SetJson: js})
	require.NoError(t, err)

	parentUID := res.GetUids()["parent"]

	update := Node{
		UID:  res.GetUids()["parent"],
		Type: "Node",
		Child: &Node{
			UID:  "_:child",
			Type: "Node",
			Name: "child replacement",
		},
	}

	js, err = json.Marshal(update)
	require.NoError(t, err)

	res, err = dg.NewTxn().Mutate(context.Background(), &api.Mutation{CommitNow: true, SetJson: js})
	assert.NoError(t, err)

	q := `
query {
  n(func: uid(%s)) {
    uid
    name
    child {
      uid
      name
    }
  }
}
`

	queryRes, err := dg.NewReadOnlyTxn().Query(context.Background(), fmt.Sprintf(q, parentUID))
	require.NoError(t, err)

	var actual map[string][]Node
	err = json.Unmarshal(queryRes.GetJson(), &actual)
	require.NoError(t, err)

	require.Len(t, actual["n"], 1)
	assert.Equal(t, "parent", actual["n"][0].Name)
	assert.Equal(t, "child replacement", actual["n"][0].Child.Name)
}