[Feature Request] Required container attributes can have empty values

[tobyspark]

Modelling empty lists and sets by omitting the property is understandable from a storage perspective, but adds overhead to the business logic consuming the objects. As a modelling layer over DynamoDB, ElectroDB could abstract this storage requirement away.

Feature Request – The required property of list and set attributes should allow empty sets and lists, marshalling to and from null behind the scenes.

[misterjoshua]

For context, are you speaking about something like this?

/* Model queries, see results, share with friends */

import { Entity, Service } from "electrodb";

const table = "your_table_name";

/* Tasks Entity */
const listHolder = new Entity(
  {
    model: {
      entity: "listHolder",
      version: "1",
      service: "app"
    },
    attributes: {
      id: {
        type: 'string',
        required: true,
      },
      set: {
        type: 'set',
        items: 'string',
        required: true,
        default: [],
      },
    },
    indexes: {
      main: {
        pk: {
          field: 'pk',
          composite: ['id'],
        }
      }
    }
  },
  { table }
);

async function demonstrateIssue() {
  await listHolder
    .create({ id: 'example', set: [] })
    .go();

  const { data } = await listHolder
    .get({ id: 'example' })
    .go();

  if (!data) return;

  console.log(data.set.length); // TypeError: Cannot read property 'length' of undefined
}

This one got me today.

[0815Hunter]

Our workaround:

• set convertEmptyValues: true

DynamoDBDocumentClient.from(ddbClient, {
    marshallOptions: {
        convertEmptyValues: true, 
    },
})

Note that convertEmptyValues: true also sets empty strings / blobs to null, so you have to use a get() hook there too.

• use a get() hook to replace null values:

attributes: {
        set: {
            type: 'set',
            required: true,
            items: ['A', 'B', 'C'] as const,
            get: (val: any, item: any) => val !== null ? val : [],
        },
    },

It's weird that the document client allows empty strings, but doesn't allow empty sets, even though it's possible to add empty sets manually in AWS.