fix(GraphQL): Link xids properly if there are duplicate xids within t…

…he same add request. (#6265)

Fixes GRAPHQL-641

See https://discuss.dgraph.io/t/residual-issue-linking-grandchild-in-mutation-with-custom-ids/9613 for the issue details.

If the same nested xid was used as a leaf node within an addType mutation, it was only linked the first time that it was used and not subsequently for later objects. This change fixes that by adding the linkage mutations and only removing the mutation which was creating the object with the xid again.

graphql/e2e/common/common.go

@@ -305,6 +305,7 @@ func RunAll(t *testing.T) {
 	t.Run("deep mutations", deepMutations)
 	t.Run("add multiple mutations", testMultipleMutations)
 	t.Run("deep XID mutations", deepXIDMutations)
+	t.Run("three level xid", testThreeLevelXID)
 	t.Run("error in multiple mutations", addMultipleMutationWithOneError)
 	t.Run("dgraph directive with reverse edge adds data correctly",
 		addMutationWithReverseDgraphEdge)

graphql/e2e/common/mutation.go

@@ -567,6 +567,260 @@ func deepXIDMutations(t *testing.T) {
 	deepXIDTest(t, postExecutor)
 }
 
+func addComments(t *testing.T, ids []string) {
+	input := []map[string]interface{}{}
+	for _, id := range ids {
+		input = append(input, map[string]interface{}{"id": id})
+	}
+
+	params := &GraphQLParams{
+		Query: `mutation($input: [AddComment1Input!]!) {
+			addComment1(input: $input) {
+			  comment1 {
+				id
+			  }
+			}
+		  }`,
+		Variables: map[string]interface{}{
+			"input": input,
+		},
+	}
+
+	gqlResponse := postExecutor(t, graphqlURL, params)
+	RequireNoGQLErrors(t, gqlResponse)
+}
+
+func testThreeLevelXID(t *testing.T) {
+
+	input := `{
+		"input": [
+			{
+				"id": "post1",
+				"comments": [
+					{
+						"id": "comment1",
+						"replies": [
+							{
+								"id": "reply1"
+							}
+						]
+					}
+				]
+			},
+			{
+				"id": "post2",
+				"comments": [
+					{
+						"id": "comment2",
+						"replies": [
+							{
+								"id": "reply1"
+							}
+						]
+					}
+				]
+			}
+		]
+	}`
+
+	qinput := make(map[string]interface{})
+	err := json.Unmarshal([]byte(input), &qinput)
+	require.NoError(t, err)
+
+	addPostParams := &GraphQLParams{
+		Query: ` mutation($input: [AddPost1Input!]!) {
+		addPost1(input: $input) {
+			post1(order: { asc: id }) {
+				id
+				comments {
+					id
+					replies {
+						id
+					}
+				}
+			}
+		}
+	}`,
+		Variables: qinput,
+	}
+
+	bothCommentsLinkedToReply := `{
+		"addPost1": {
+		  "post1": [
+			{
+			  "id": "post1",
+			  "comments": [
+				{
+				  "id": "comment1",
+				  "replies": [
+					{
+					  "id": "reply1"
+					}
+				  ]
+				}
+			  ]
+			},
+			{
+			  "id": "post2",
+			  "comments": [
+				{
+				  "id": "comment2",
+				  "replies": [
+					{
+					  "id": "reply1"
+					}
+				  ]
+				}
+			  ]
+			}
+		  ]
+		}
+	}`
+
+	firstCommentLinkedToReply := `{
+		"addPost1": {
+		  "post1": [
+			{
+			  "id": "post1",
+			  "comments": [
+				{
+				  "id": "comment1",
+				  "replies": [
+					{
+					  "id": "reply1"
+					}
+				  ]
+				}
+			  ]
+			},
+			{
+			  "id": "post2",
+			  "comments": [
+				{
+				  "id": "comment2",
+				  "replies": []
+				}
+			  ]
+			}
+		  ]
+		}
+	}`
+
+	secondCommentLinkedToReply := `{
+		"addPost1": {
+		  "post1": [
+			{
+			  "id": "post1",
+			  "comments": [
+				{
+				  "id": "comment1",
+				  "replies": []
+				}
+			  ]
+			},
+			{
+			  "id": "post2",
+			  "comments": [
+				{
+				  "id": "comment2",
+				  "replies": [
+					{
+					  "id": "reply1"
+					}
+				  ]
+				}
+			  ]
+			}
+		  ]
+		}
+	}`
+
+	noCommentsLinkedToReply := `{
+		"addPost1": {
+		  "post1": [
+			{
+			  "id": "post1",
+			  "comments": [
+				{
+				  "id": "comment1",
+				  "replies": []
+				}
+			  ]
+			},
+			{
+			  "id": "post2",
+			  "comments": [
+				{
+				  "id": "comment2",
+				  "replies": []
+				}
+			  ]
+			}
+		  ]
+		}
+	}`
+
+	cases := map[string]struct {
+		Comments                   []string
+		Expected                   string
+		ExpectedNumDeletedComments int
+	}{
+		"2nd level nodes don't exist but third level does": {
+			[]string{"reply1"},
+			bothCommentsLinkedToReply,
+			3,
+		},
+		"2nd level and third level nodes don't exist": {
+			[]string{},
+			bothCommentsLinkedToReply,
+			3,
+		},
+		"2nd level node exists but third level doesn't": {
+			[]string{"comment1", "comment2"},
+			noCommentsLinkedToReply,
+			2,
+		},
+		"2nd level and third level nodes exist": {
+			[]string{"comment1", "comment2", "reply1"},
+			noCommentsLinkedToReply,
+			3,
+		},
+		"one 2nd level node exists and third level node exists": {
+			[]string{"comment1", "reply1"},
+			secondCommentLinkedToReply,
+			3,
+		},
+		"the other 2nd level node exists and third level node exists": {
+			[]string{"comment2", "reply1"},
+			firstCommentLinkedToReply,
+			3,
+		},
+		"one 2nd level node exists and third level node doesn't exist": {
+			[]string{"comment1"},
+			secondCommentLinkedToReply,
+			3,
+		},
+		"other 2nd level node exists and third level node doesn't exist": {
+			[]string{"comment2", "reply1"},
+			firstCommentLinkedToReply,
+			3,
+		},
+	}
+
+	for name, tc := range cases {
+		t.Run(name, func(t *testing.T) {
+			addComments(t, tc.Comments)
+			gqlResponse := postExecutor(t, graphqlURL, addPostParams)
+			RequireNoGQLErrors(t, gqlResponse)
+			testutil.CompareJSON(t, tc.Expected, string(gqlResponse.Data))
+
+			deleteGqlType(t, "Post1", map[string]interface{}{}, 2, nil)
+			deleteGqlType(t, "Comment1", map[string]interface{}{}, tc.ExpectedNumDeletedComments,
+				nil)
+		})
+	}
+}
+
 func deepXIDTest(t *testing.T, executeRequest requestExecutor) {
 	newCountry := &country{
 		Name: "A Country",