如何在GraphQL解析器中使用多个API调用来构造承诺数组，以返回单个对象类型列表

Question

I'm stuck in my GraphQL resolver fetching todo-lists for a particular user belonging to a company. According to whether or not they have access to all todo-lists or a certain few, it will fetch for groups the user registered to that have belonging todo-lists, and those should be fetched.

The code so far is capable of logging the requested todo-lists on the query but I have yet to come to the solution on how to actually return data of all of the user's registered groups's todo-lists.

I chose to export the actual logic into a separate function

The Resolver:

allowedListItems: {
  type: new GraphQLList(TodoItem),
  resolve(parentValue, args) {
    return Promise.all([fetchAllowedItems(parentValue._id)]);
  }
},

The Promise Function

function fetchAllowedItems(userId) {
  return User.findOne({ _id: userId }).then((user) => {
    if (user.todoGroups) {
      return user.todoGroups.map((groupId) => {
        return TodoGroup.findOne({ _id: groupId }).then(group => {
          return group.todoLists.map((listId) => {
            return TodoList.findOne({ _id: listId })
          })
        })
      })
    } else {
      return TodoList.find({ company: parentValue.company }).exec();
    }
  })
}

I am not getting any errors from GraphQL so I guess it's about the way I make the promisses return to the resolver, I'd appreciate a lot if you can help me out!

Update:

I should wrap the maps with a Promise.all, as the mapping returns an array. Though the updated code brings no improvement in the returned data.

async resolve(parentValue, args) {
    let user = await User.findOne({ _id: parentValue._id })

    if (user.todoGroups) {
      return Promise.all(user.todoGroups.map((groupId) => {
        return TodoGroup.findOne({ _id: groupId }).then(group => {
          return Promise.all(group.todoLists.map((listId) => {
            return TodoList.findOne({ _id: listId });
          }))
        })
      }))
    } else {
      return TodoList.find({ company: parentValue.company }).exec();
    }
  }
},

Current query result:

{
  "data": {
    "user": {
      "_id": "5ba11690ad7a93d2b34d21a9",
      "allowedTodos": [
        {
          "_id": null,
          "title": null
        }
      ]
    }
  }
}

Answer 1

You need to call Promise.all on an array of promises, not a promise for that. Also you'll have to call it on each level:

allowedListItems: {
  type: new GraphQLList(TodoItem),
  resolve(parentValue, args) {
    return User.findOne({ _id: parentValue._id }).then(user => {
      if (user.todoGroups) {
        return Promise.all(user.todoGroups.map(groupId => {
//             ^^^^^^^^^^^^
          return TodoGroup.findOne({ _id: groupId }).then(group => {
            return Promise.all(group.todoLists.map(listId => {
//                 ^^^^^^^^^^^^
              return TodoList.findOne({ _id: listId })
            }));
          });
        }));
      } else {
        return TodoList.find({ company: parentValue.company }).exec();
      }
    });
  }
}