added a fallback strategy for denormalization

[bjartebore]

Problem

In some cases I would like to denormalize a structure with a list of Ids instead of a list of subobjects (reasons could be to limit fetched data). When i normalize this structure the normalization works, I am left with the entity ids, but there is no way to create stubs for the entities itself, which I find ok since there could be an instance of the same object somewhere else in the structure.

But when denormalizing this I will get back an array with undefined items.

Solution

A possible solution to this could be to add a possibility to add a fallbackStrategy option to the EntitySchema where we could write our own fallback method for denormalization.

TODO

• Add & update tests
• Ensure CI is passing (lint, tests, flow)
• Update relevant documentation

[bjartebore]

#421

[coveralls]

Coverage remained the same at 100.0% when pulling 65439eb on bjartebore:master into a8ac881 on paularmstrong:master.

[paularmstrong]

I like that this has a very low added complexity. Though I feel like it needs really strong documentation with example code of when and why you would use it. Can you please add to the docs?

[bjartebore]

I have updated the relevant documentation, I hope it will suffice :)

[paularmstrong]

Thanks!

[mecp]

Hi guys, Is there a way to skip missing references while denormalizing to avoid having [undefined, undefined, undefined] situation?

for example here, in a use case I have, I want denormalizer to return c: [] instead of c: [undefined, undefined, undefined]

const { schema, denormalize } = require('normalizr');

const a = {
  id: 1,
  b: 1,
  c: [1, 2, 3]
}

const cSchema = new schema.Entity('c');
const aSchema = new schema.Entity('a', { c: [cSchema] });

const result = denormalize([1], [aSchema], { a: { 1: a }, c: {} })

available to run here https://runkit.com/mecp/5eb5baa8aad698001bb12788