Exposed custom projection builders and ProjectionDefinition types

It appeared that ProjectionDefinition types were not exposed and that caused issues with setting up custom projections. Added builders to make that easier. Reshaped also ProjectionDefnition helper method moving connection string and client to second context parameter. Thanks to that users that don't need it will have a simpler handle method definition.
event-driven-io · Aug 5, 2024 · 23904b8 · 23904b8
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diff --git a/samples/webApi/expressjs-with-postgresql/README.md b/samples/webApi/expressjs-with-postgresql/README.md
@@ -2,13 +2,13 @@
 
 ![](./docs/public/logo.png)
 
-# Emmett - Sample showing event-sourced WebApi with Express.js and EventStoreDB
+# Emmett - Sample showing event-sourced WebApi with Express.js and PostgreSQL
 
 Read more in [Emmett getting started guide](https://event-driven-io.github.io/emmett/getting-started.html).
 
 ## Prerequisities
 
-Sample require EventStoreDB, you can start it by running
+Sample require PostgreSQL, you can start it by running
 
 ```bash
 docker-compose up

diff --git a/src/package-lock.json b/src/package-lock.json
diff --git a/src/package.json b/src/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@event-driven-io/core",
-  "version": "0.13.0",
+  "version": "0.14.0",
   "description": "Emmett - Event Sourcing development made simple",
   "engines": {
     "node": ">=20.11.1"

diff --git a/src/packages/emmett-esdb/package.json b/src/packages/emmett-esdb/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@event-driven-io/emmett-esdb",
-  "version": "0.13.0",
+  "version": "0.14.0",
   "description": "Emmett - EventStoreDB - Event Sourcing development made simple",
   "scripts": {
     "build": "tsup",
@@ -50,7 +50,7 @@
     "@event-driven-io/emmett-testcontainers": "^0.5.0"
   },
   "peerDependencies": {
-    "@event-driven-io/emmett": "0.13.0",
+    "@event-driven-io/emmett": "0.14.0",
     "@eventstore/db-client": "^6.1.0"
   }
 }
diff --git a/src/packages/emmett-expressjs/package.json b/src/packages/emmett-expressjs/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@event-driven-io/emmett-expressjs",
-  "version": "0.13.0",
+  "version": "0.14.0",
   "description": "Emmett - Event Sourcing development made simple",
   "scripts": {
     "build": "tsup",
@@ -48,7 +48,7 @@
   "dependencies": {},
   "devDependencies": {},
   "peerDependencies": {
-    "@event-driven-io/emmett": "0.13.0",
+    "@event-driven-io/emmett": "0.14.0",
     "@types/express": "4.17.21",
     "@types/supertest": "6.0.2",
     "express": "4.19.2",

diff --git a/src/packages/emmett-fastify/package.json b/src/packages/emmett-fastify/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@event-driven-io/emmett-fastify",
-  "version": "0.13.0",
+  "version": "0.14.0",
   "description": "Emmett - Event Sourcing development made simple",
   "scripts": {
     "build": "tsup",
@@ -52,7 +52,7 @@
   "dependencies": {},
   "devDependencies": {},
   "peerDependencies": {
-    "@event-driven-io/emmett": "^0.13.0",
+    "@event-driven-io/emmett": "^0.14.0",
     "fastify": "4.26.2",
     "@fastify/compress": "7.0.0",
     "@fastify/etag": "5.1.0",

diff --git a/src/packages/emmett-postgresql/package.json b/src/packages/emmett-postgresql/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@event-driven-io/emmett-postgresql",
-  "version": "0.13.0",
+  "version": "0.14.0",
   "description": "Emmett - PostgreSQL - Event Sourcing development made simple",
   "scripts": {
     "build": "tsup",
@@ -52,7 +52,7 @@
     "@event-driven-io/emmett-testcontainers": "^0.5.0"
   },
   "peerDependencies": {
-    "@event-driven-io/emmett": "0.13.0",
+    "@event-driven-io/emmett": "0.14.0",
     "@types/pg": "^8.11.6",
     "@types/pg-format": "^1.0.5",
     "pg": "^8.12.0",

diff --git a/src/packages/emmett-postgresql/src/eventStore/index.ts b/src/packages/emmett-postgresql/src/eventStore/index.ts
@@ -1,2 +1,3 @@
 export * from './postgreSQLEventStore';
+export * from './projections';
 export * from './schema';
diff --git a/src/packages/emmett-postgresql/src/eventStore/postgreSQLEventStore.e2e.spec.ts b/src/packages/emmett-postgresql/src/eventStore/postgreSQLEventStore.e2e.spec.ts
@@ -1,4 +1,9 @@
-import { assertDeepEqual, assertIsNotNull } from '@event-driven-io/emmett';
+import {
+  assertDeepEqual,
+  assertEqual,
+  assertIsNotNull,
+  type ReadEvent,
+} from '@event-driven-io/emmett';
 import { pongoClient, type PongoClient } from '@event-driven-io/pongo';
 import {
   PostgreSqlContainer,
@@ -20,6 +25,7 @@ import {
   getPostgreSQLEventStore,
   type PostgresEventStore,
 } from './postgreSQLEventStore';
+import { inlineProjection } from './projections';
 import { pongoSingleProjection } from './projections/pongo';
 
 void describe('EventStoreDBEventStore', async () => {
@@ -32,7 +38,7 @@ void describe('EventStoreDBEventStore', async () => {
     postgres = await new PostgreSqlContainer().start();
     connectionString = postgres.getConnectionUri();
     eventStore = getPostgreSQLEventStore(connectionString, {
-      projections: [shoppingCartShortInfoProjection],
+      projections: [shoppingCartShortInfoProjection, customProjection],
     });
     pongo = pongoClient(connectionString);
     return eventStore;
@@ -60,6 +66,7 @@ void describe('EventStoreDBEventStore', async () => {
     };
     const discount = 10;
     const shoppingCartId = `shopping_cart-${uuid()}`;
+    handledEventsInCustomProjection = [];
 
     await eventStore.appendToStream<ShoppingCartEvent>(shoppingCartId, [
       { type: 'ProductItemAdded', data: { productItem } },
@@ -87,6 +94,8 @@ void describe('EventStoreDBEventStore', async () => {
         totalAmount: 54,
       },
     );
+
+    assertEqual(3, handledEventsInCustomProjection.length);
   });
 });
 
@@ -126,3 +135,13 @@ const shoppingCartShortInfoProjection = pongoSingleProjection(
   'ProductItemAdded',
   'DiscountApplied',
 );
+
+let handledEventsInCustomProjection: ReadEvent<ShoppingCartEvent>[] = [];
+
+const customProjection = inlineProjection<ShoppingCartEvent>({
+  name: 'customProjection',
+  canHandle: ['ProductItemAdded', 'DiscountApplied'],
+  handle: (events) => {
+    handledEventsInCustomProjection.push(...events);
+  },
+});
diff --git a/src/packages/emmett-postgresql/src/eventStore/projections/index.ts b/src/packages/emmett-postgresql/src/eventStore/projections/index.ts
@@ -6,10 +6,14 @@ import {
 import pg from 'pg';
 import type { PostgresEventStoreOptions } from '../postgreSQLEventStore';
 
+export type ProjectionHandlerContext = {
+  connectionString: string;
+  client: pg.PoolClient;
+};
+
 export type PostgresProjectionHandler<EventType extends Event = Event> = (
-  connectionString: string,
-  client: pg.PoolClient,
   events: ReadEvent<EventType>[],
+  context: ProjectionHandlerContext,
 ) => Promise<void> | void;
 
 export type ProjectionDefintion<EventType extends Event = Event> = {
@@ -36,6 +40,14 @@ export const handleProjections = async <EventType extends Event = Event>(
   );
 
   for (const projection of projections) {
-    await projection.handle(connectionString, client, events);
+    await projection.handle(events, { connectionString, client });
   }
 };
+
+export const projection = <EventType extends Event>(
+  definition: ProjectionDefintion<EventType>,
+): ProjectionDefintion => definition as unknown as ProjectionDefintion;
+
+export const inlineProjection = <EventType extends Event>(
+  definition: Omit<ProjectionDefintion<EventType>, 'type'>,
+): ProjectionDefintion => projection({ type: 'inline', ...definition });
diff --git a/src/packages/emmett-postgresql/src/eventStore/projections/pongo.ts b/src/packages/emmett-postgresql/src/eventStore/projections/pongo.ts
@@ -9,7 +9,7 @@ import {
   type PongoDocument,
 } from '@event-driven-io/pongo';
 import pg from 'pg';
-import { type ProjectionDefintion } from './';
+import { inlineProjection, type ProjectionDefintion } from './';
 
 export type PongoProjectionOptions<EventType extends Event> = {
   documentId: (event: ReadEvent<EventType>) => string;
@@ -41,18 +41,14 @@ export const pongoProjection = <EventType extends Event>(
   handle: (pongo: PongoClient, events: ReadEvent<EventType>[]) => Promise<void>,
   ...canHandle: EventTypeOf<EventType>[]
 ): ProjectionDefintion =>
-  ({
-    type: 'inline',
+  inlineProjection<EventType>({
     canHandle,
-    handle: async (
-      connectionString: string,
-      client: pg.PoolClient,
-      events: ReadEvent<EventType>[],
-    ) => {
+    handle: async (events, context) => {
+      const { connectionString, client } = context;
       const pongo = pongoClient(connectionString, { client });
       await handle(pongo, events);
     },
-  }) as unknown as ProjectionDefintion;
+  });
 
 export const pongoMultiStreamProjection = <
   Document extends PongoDocument,

diff --git a/src/packages/emmett-testcontainers/package.json b/src/packages/emmett-testcontainers/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@event-driven-io/emmett-testcontainers",
-  "version": "0.13.0",
+  "version": "0.14.0",
   "description": "Emmett - TestContainers - Event Sourcing development made simple",
   "scripts": {
     "build": "tsup",
@@ -46,7 +46,7 @@
     "dist"
   ],
   "dependencies": {
-    "@event-driven-io/emmett": "0.13.0",
+    "@event-driven-io/emmett": "0.14.0",
     "testcontainers": "^10.7.2"
   },
   "devDependencies": {

diff --git a/src/packages/emmett/package.json b/src/packages/emmett/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@event-driven-io/emmett",
-  "version": "0.13.0",
+  "version": "0.14.0",
   "description": "Emmett - Event Sourcing development made simple",
   "scripts": {
     "build": "tsup",