Handle missing data in denormalize

[jeffcarbs]

Following from discussion here #228 (comment)

Problem

When an entity is not found during denormalization, it throws an unexpected exception.

const mySchema = new schema.Entity('tacos');
const entities = {
  tacos: {
    1: { id: 1, type: 'foo' }
  }
};

denormalize(3, mySchema, entities)
> TypeError: Cannot read property 'id' of undefined
    at EntitySchema._getId (~/normalizr/dist/normalizr.js:226:65)
    at EntitySchema.getId (~/normalizr/dist/normalizr.js:245:19)
    at ~/normalizr/dist/normalizr.js:635:21
    at EntitySchema.denormalize (~/normalizr/dist/normalizr.js:273:20)
    at unvisit (~/normalizr/dist/normalizr.js:612:17)
    at Object.denormalize$1 [as denormalize] (~/normalizr/dist/normalizr.js:651:10)
    at repl:1:3
    at realRunInThisContextScript (vm.js:22:35)
    at sigintHandlersWrap (vm.js:98:12)
    at ContextifyScript.Script.runInThisContext (vm.js:24:12)

Solution

During denormalization, if an entity is not found return undefined in its place.

NOTE: Initially I returned null where missing (null or undefined) data was. I've updated it to handle missing data by returning whatever was there, respecting either null or undefined.

TODO

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

[jeffcarbs]

Discovered a fun fact about javascript while debugging this: typeof null === 'object'

[coveralls]

Coverage decreased (-0.6%) to 99.419% when pulling 4d43c07 on jcarbo:feature/handle-not-found into fcee566 on paularmstrong:master.

[jeffcarbs]

Note there's a similar PR that was recently closed: #229.

That PR returns null for the entire denormalize call if any data is missing, this PR will put undefined at the spot of the missing data. For example:

const foodSchema = new schema.Entity('foods');
const menuSchema = new schema.Entity('menus', {
  food: foodSchema
});

const entities = {
  menus: {
    1: { id: 1, food: 2 }
  },
  foods: {
    1: { id: 1 }
  }
};

// On PR #229
denormalize(1, mySchema, entities) === null
denormalize(2, mySchema, entities) === null

// On this PR
denormalize(1, mySchema, entities) === {
  "food": undefined,
  "id": 1,
}
denormalize(2, mySchema, entities) === undefined

[coveralls]

Coverage remained the same at 100.0% when pulling 88136e1 on jcarbo:feature/handle-not-found into fcee566 on paularmstrong:master.

[paularmstrong]

🎉 looks good to me!

[paularmstrong]

@jcarbo looks like you maybe don't check twitter anymore. Your changes have been published to v3.2.0

[jeffcarbs]

Thanks for the quick review/merge!

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.