Added optional getDocumentId selector for single stream projection

Thanks to that, one can still use custom id based on the event data

src/packages/emmett-postgresql/src/eventStore/projections/pongo/projections.ts

@@ -167,6 +167,7 @@ export type PongoSingleStreamProjectionOptions<
     PostgresReadEventMetadata = PostgresReadEventMetadata,
 > = {
   canHandle: CanHandle<EventType>;
+  getDocumentId?: (event: ReadEvent<EventType>) => string;
 
   collectionName: string;
 } & (
@@ -201,6 +202,7 @@ export const pongoSingleStreamProjection = <
 ): PostgreSQLProjectionDefinition => {
   return pongoMultiStreamProjection<Document, EventType, EventMetaDataType>({
     ...options,
-    getDocumentId: (event) => event.metadata.streamName,
+    getDocumentId:
+      options.getDocumentId ?? ((event) => event.metadata.streamName),
   });
 };

src/packages/emmett-postgresql/src/eventStore/projections/postgresProjection.customid.int.spec.ts

@@ -0,0 +1,118 @@
+import type { Event } from '@event-driven-io/emmett';
+import {
+  PostgreSqlContainer,
+  StartedPostgreSqlContainer,
+} from '@testcontainers/postgresql';
+import { after, before, beforeEach, describe, it } from 'node:test';
+import { v4 as uuid } from 'uuid';
+import {
+  expectPongoDocuments,
+  pongoSingleStreamProjection,
+  PostgreSQLProjectionSpec,
+} from '.';
+import type {
+  DiscountApplied,
+  PricedProductItem,
+} from '../../testing/shoppingCart.domain';
+
+export type ProductItemAdded = Event<
+  'ProductItemAdded',
+  { productItem: PricedProductItem; shoppingCartId: string }
+>;
+
+void describe('Postgres Projections', () => {
+  let postgres: StartedPostgreSqlContainer;
+  let connectionString: string;
+  let given: PostgreSQLProjectionSpec<ProductItemAdded | DiscountApplied>;
+  let shoppingCartId: string;
+  let streamName: string;
+
+  before(async () => {
+    postgres = await new PostgreSqlContainer().start();
+    connectionString = postgres.getConnectionUri();
+
+    given = PostgreSQLProjectionSpec.for({
+      projection: shoppingCartShortInfoProjection,
+      connectionString,
+    });
+  });
+
+  beforeEach(() => {
+    shoppingCartId = uuid();
+    streamName = `shoppingCart:${shoppingCartId}`;
+  });
+
+  after(async () => {
+    try {
+      await postgres.stop();
+    } catch (error) {
+      console.log(error);
+    }
+  });
+
+  void it('uses custom document id instead of stream name assigned in projection evolve', () =>
+    given([])
+      .when([
+        {
+          type: 'ProductItemAdded',
+          data: {
+            productItem: { price: 100, productId: 'shoes', quantity: 100 },
+            shoppingCartId,
+          },
+          metadata: {
+            streamName,
+          },
+        },
+      ])
+      .then(
+        expectPongoDocuments
+          .fromCollection<ShoppingCartShortInfo>(
+            shoppingCartShortInfoCollectionName,
+          )
+          .withId(shoppingCartId)
+          .toBeEqual({
+            _id: shoppingCartId,
+            productItemsCount: 100,
+            totalAmount: 10000,
+          }),
+      ));
+});
+
+type ShoppingCartShortInfo = {
+  _id?: string;
+  productItemsCount: number;
+  totalAmount: number;
+};
+
+const shoppingCartShortInfoCollectionName = 'shoppingCartShortInfo';
+
+const evolve = (
+  document: ShoppingCartShortInfo,
+  { type, data: event }: ProductItemAdded,
+): ShoppingCartShortInfo => {
+  switch (type) {
+    case 'ProductItemAdded':
+      return {
+        ...document,
+        _id: event.shoppingCartId,
+        totalAmount:
+          document.totalAmount +
+          event.productItem.price * event.productItem.quantity,
+        productItemsCount:
+          document.productItemsCount + event.productItem.quantity,
+      };
+    default:
+      return document;
+  }
+};
+
+const shoppingCartShortInfoProjection = pongoSingleStreamProjection({
+  collectionName: shoppingCartShortInfoCollectionName,
+  evolve,
+  getDocumentId: (event) => event.data.shoppingCartId,
+  canHandle: ['ProductItemAdded'],
+  initialState: () => ({
+    productItemsCount: 0,
+    totalAmount: 0,
+  }),
+});