feat(parser): implement parser decorator (#1831)

packages/parser/src/middleware/parser.ts

@@ -1,12 +1,7 @@
 import { type MiddyLikeRequest } from '@aws-lambda-powertools/commons/types';
 import { type MiddlewareObj } from '@middy/core';
 import { type ZodSchema } from 'zod';
-import { type Envelope } from '../types/envelope.js';
-
-interface ParserOptions<S extends ZodSchema> {
-  schema: S;
-  envelope?: Envelope;
-}
+import { type ParserOptions } from '../types/ParserOptions.js';
 
 /**
  * A middiy middleware to parse your event.

packages/parser/src/parser.ts

@@ -0,0 +1,59 @@
+import { HandlerMethodDecorator } from '@aws-lambda-powertools/commons/types';
+import { Context, Handler } from 'aws-lambda';
+import { ZodSchema } from 'zod';
+import { type ParserOptions } from './types/ParserOptions.js';
+
+/**
+ * A decorator to parse your event.
+ *
+ * @example
+ * ```typescript
+ *
+ * import { parser } from '@aws-lambda-powertools/parser';
+ * import { sqsEnvelope } from '@aws-lambda-powertools/parser/envelopes/sqs';
+ *
+ *
+ * const Order = z.object({
+ *  orderId: z.string(),
+ *  description: z.string(),
+ * }
+ *
+ * class Lambda extends LambdaInterface {
+ *
+ *   @parser({ envelope: sqsEnvelope, schema: OrderSchema })
+ *   public async handler(event: Order, _context: Context): Promise<unknown> {
+ *   // sqs event is parsed and the payload is extracted and parsed
+ *   // apply business logic to your Order event
+ *   const res = processOrder(event);
+ *   return res;
+ *   }
+ * }
+ *
+ * @param options
+ */
+const parser = <S extends ZodSchema>(
+  options: ParserOptions<S>
+): HandlerMethodDecorator => {
+  return (_target, _propertyKey, descriptor) => {
+    const original = descriptor.value!;
+
+    const { schema, envelope } = options;
+
+    descriptor.value = async function (
+      this: Handler,
+      event: unknown,
+      context: Context,
+      callback
+    ) {
+      const parsedEvent = envelope
+        ? envelope(event, schema)
+        : schema.parse(event);
+
+      return original.call(this, parsedEvent, context, callback);
+    };
+
+    return descriptor;
+  };
+};
+
+export { parser };

packages/parser/src/types/ParserOptions.ts

@@ -0,0 +1,9 @@
+import type { ZodSchema } from 'zod';
+import { Envelope } from './envelope.js';
+
+type ParserOptions<S extends ZodSchema> = {
+  schema: S;
+  envelope?: Envelope;
+};
+
+export { type ParserOptions };

packages/parser/tests/unit/parser.decorator.test.ts

@@ -0,0 +1,118 @@
+/**
+ * Test decorator parser
+ *
+ * @group unit/parser
+ */
+
+import { LambdaInterface } from '@aws-lambda-powertools/commons/lib/esm/types';
+import { Context, EventBridgeEvent } from 'aws-lambda';
+import { parser } from '../../src/parser';
+import { TestSchema, TestEvents } from './schema/utils';
+import { generateMock } from '@anatine/zod-mock';
+import { eventBridgeEnvelope } from '../../src/envelopes/event-bridge';
+import { EventBridgeSchema } from '../../src/schemas/eventbridge';
+import { z } from 'zod';
+
+describe('Parser Decorator', () => {
+  const customEventBridgeSchema = EventBridgeSchema.extend({
+    detail: TestSchema,
+  });
+
+  type TestSchema = z.infer<typeof TestSchema>;
+
+  class TestClass implements LambdaInterface {
+    @parser({ schema: TestSchema })
+    public async handler(
+      event: TestSchema,
+      _context: Context
+    ): Promise<unknown> {
+      return event;
+    }
+
+    @parser({ schema: customEventBridgeSchema })
+    public async handlerWithCustomSchema(
+      event: unknown,
+      _context: Context
+    ): Promise<unknown> {
+      return event;
+    }
+
+    @parser({ schema: TestSchema, envelope: eventBridgeEnvelope })
+    public async handlerWithParserCallsAnotherMethod(
+      event: unknown,
+      _context: Context
+    ): Promise<unknown> {
+      return this.anotherMethod(event as TestSchema);
+    }
+
+    @parser({ envelope: eventBridgeEnvelope, schema: TestSchema })
+    public async handlerWithSchemaAndEnvelope(
+      event: unknown,
+      _context: Context
+    ): Promise<unknown> {
+      return event;
+    }
+
+    private async anotherMethod(event: TestSchema): Promise<TestSchema> {
+      return event;
+    }
+  }
+
+  const lambda = new TestClass();
+
+  it('should parse custom schema event', async () => {
+    const testEvent = generateMock(TestSchema);
+
+    const resp = await lambda.handler(testEvent, {} as Context);
+
+    expect(resp).toEqual(testEvent);
+  });
+
+  it('should parse custom schema with envelope event', async () => {
+    const customPayload = generateMock(TestSchema);
+    const testEvent = TestEvents.eventBridgeEvent as EventBridgeEvent<
+      string,
+      unknown
+    >;
+    testEvent.detail = customPayload;
+
+    const resp = await lambda.handlerWithSchemaAndEnvelope(
+      testEvent,
+      {} as Context
+    );
+
+    expect(resp).toEqual(customPayload);
+  });
+
+  it('should parse extended envelope event', async () => {
+    const customPayload = generateMock(TestSchema);
+
+    const testEvent = generateMock(customEventBridgeSchema);
+    testEvent.detail = customPayload;
+
+    const resp: z.infer<typeof customEventBridgeSchema> =
+      (await lambda.handlerWithCustomSchema(
+        testEvent,
+        {} as Context
+      )) as z.infer<typeof customEventBridgeSchema>;
+
+    expect(customEventBridgeSchema.parse(resp)).toEqual(testEvent);
+    expect(resp.detail).toEqual(customPayload);
+  });
+
+  it('should parse and call private async method', async () => {
+    const customPayload = generateMock(TestSchema);
+    const testEvent = TestEvents.eventBridgeEvent as EventBridgeEvent<
+      string,
+      unknown
+    >;
+    testEvent.detail = customPayload;
+
+    const resp = await lambda.handlerWithParserCallsAnotherMethod(
+      testEvent,
+      {} as Context
+    );
+
+    expect(resp).toEqual(customPayload);
+  });
+});