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Allow EntityManager.create to infer EntityInstance type #364

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Allow EntityManager.create to infer EntityInstance type #364

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6926b91
feat(entity): infer entity type in `create`
bengreenier Sep 27, 2023
bb30b57
fix(lint): remove unused type
bengreenier Sep 27, 2023
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31 changes: 27 additions & 4 deletions packages/core/src/classes/manager/__test__/entity-manager.spec.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,6 @@ import {
import {Connection} from '../../connection/connection';
import {
CONSUMED_CAPACITY_TYPE,
EntityInstance,
InvalidDynamicUpdateAttributeValueError,
} from '@typedorm/common';
import {
Expand Down Expand Up @@ -213,6 +212,30 @@ test('creates entity and returns all attributes, including auto generated ones',
});
});

test('will infer the proper return type when creating an entity', async () => {
dcMock.put.mockReturnValue({
promise: () => ({}),
});

const user = new User();
user.id = '1';
user.name = 'Test User';
user.status = 'active';

const ret = await manager.create(user);

type Expect<T extends true> = T;
type Equal<X, Y> = (<T>() => T extends X ? 1 : 2) extends <T>() => T extends Y
? 1
: 2
? true
: false;

// would fail to compile if the types did not match
// eslint-disable-next-line @typescript-eslint/no-unused-vars
type Assert = Expect<Equal<typeof ret, User>>;
});

/**
* Issue: #203
*/
Expand All @@ -236,9 +259,9 @@ test('will throw when called with a POJO rather than an instance of a entity cla
addresses: ['address a'],
};

await expect(
manager.create<User>(userProperties as EntityInstance)
).rejects.toBeInstanceOf(Error);
await expect(manager.create<User>(userProperties)).rejects.toBeInstanceOf(
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since there is now a relationship between the type parameter Entity and the first parameter, we actually can't keep this test exactly as is.

The options I see are:

  • drop the User type parameter altogether
  • drop the EntityInstance cast
  • use EntityInstance as the type parameter and keep the EntityInstance cast on the input
  • drop all the type parameters and rely on inference (which will be inferred as the POJO type)

I choose to drop the cast, as that felt the cleanest to me, in expressing the failure intent (you can't pass POJO objects in when an Entity instance is expected).

Error
);
});

/**
Expand Down
12 changes: 6 additions & 6 deletions packages/core/src/classes/manager/entity-manager.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -190,11 +190,11 @@ export class EntityManager {
* Creates new record in table with given entity
* @param entity Entity to add to table as a new record
*/
async create<Entity>(
entity: EntityInstance,
options?: EntityManagerCreateOptions<Entity>,
async create<TEntity extends EntityInstance>(
entity: TEntity,
options?: EntityManagerCreateOptions<TEntity>,
metadataOptions?: MetadataOptions
): Promise<Entity> {
): Promise<TEntity> {
if (!IsEntityInstance(entity)) {
throw new Error(
`Provided entity ${JSON.stringify(
Expand Down Expand Up @@ -231,7 +231,7 @@ export class EntityManager {
}

// by default dynamodb does not return attributes on create operation, so return one
const itemToReturn = this._entityTransformer.fromDynamoEntity<Entity>(
const itemToReturn = this._entityTransformer.fromDynamoEntity<TEntity>(
entityClass,
dynamoPutItemInput.Item as DocumentClientTypes.AttributeMap,
{
Expand All @@ -250,7 +250,7 @@ export class EntityManager {
returnConsumedCapacity: metadataOptions?.returnConsumedCapacity,
});

const itemToReturn = this._entityTransformer.fromDynamoEntity<Entity>(
const itemToReturn = this._entityTransformer.fromDynamoEntity<TEntity>(
entityClass,
// if create operation contains multiple items, first one will the original item
dynamoPutItemInput[0]?.Put?.Item ?? {},
Expand Down