docs: add parser example for built-in extension, remove event-handler missing code example reference

Author: am29d

Diff for: docs/core/event-handler/api-gateway.md

@@ -37,17 +37,5 @@ This is the sample infrastructure for API Gateway and Lambda Function URLs we ar
 
 ???+ info "There is no additional permissions or dependencies required to use this utility."
 
-=== "API Gateway SAM Template"
-
-    ```yaml title="AWS Serverless Application Model (SAM) example"
-    --8<-- "examples/snippets/event-handler/rest/templates/template.yaml"
-    ```
-
-=== "Lambda Function URL SAM Template"
-
-    ```yaml title="AWS Serverless Application Model (SAM) example"
-    --8<-- "examples/event_handler_lambda_function_url/sam/template.yaml"
-    ```
-
 <!-- remove line below while editing this doc & put it back until the doc has reached its first draft -->
-<!-- markdownlint-disable MD043 -->
+<!-- markdownlint-disable MD043 -->

Diff for: docs/utilities/parser.md

@@ -109,6 +109,23 @@ You can extend every built-in schema to include your own schema, and yet have al
     --8<-- "examples/snippets/parser/examplePayload.json"
     ```
 
+For scenarios where you have a stringiied JSON payload, you can extend the built-in schema using `.transform()` and `.pipe()` method.
+
+=== "APIGatewayProxyEventSchema"
+
+    ```typescript hl_lines="24-34"
+    --8<-- "examples/snippets/parser/extendAPIGatewaySchema.ts"
+    ```
+
+    1. parse the `body` inside `transform` method
+    2. chain your custom schema to `pipe` operation
+
+=== "Example Payload for API Gateway Event"
+
+    ```json
+    --8<-- "examples/snippets/parser/exampleAPIGatewayPayload.json"
+    ```
+
 ## Envelopes
 
 When trying to parse your payload you might encounter the following situations:

Diff for: examples/snippets/parser/exampleAPIGatewayPayload.json

@@ -0,0 +1,81 @@
+{
+  "version": "1.0",
+  "resource": "/my/path",
+  "path": "/my/path",
+  "httpMethod": "GET",
+  "headers": {
+    "Header1": "value1",
+    "Header2": "value2",
+    "Origin": "https://aws.amazon.com"
+  },
+  "multiValueHeaders": {
+    "Header1": [
+      "value1"
+    ],
+    "Header2": [
+      "value1",
+      "value2"
+    ]
+  },
+  "queryStringParameters": {
+    "parameter1": "value1",
+    "parameter2": "value"
+  },
+  "multiValueQueryStringParameters": {
+    "parameter1": [
+      "value1",
+      "value2"
+    ],
+    "parameter2": [
+      "value"
+    ]
+  },
+  "requestContext": {
+    "accountId": "123456789012",
+    "apiId": "id",
+    "authorizer": {
+      "claims": null,
+      "scopes": null
+    },
+    "domainName": "id.execute-api.us-east-1.amazonaws.com",
+    "domainPrefix": "id",
+    "extendedRequestId": "request-id",
+    "httpMethod": "GET",
+    "identity": {
+      "accessKey": null,
+      "accountId": null,
+      "caller": null,
+      "cognitoAuthenticationProvider": null,
+      "cognitoAuthenticationType": null,
+      "cognitoIdentityId": null,
+      "cognitoIdentityPoolId": null,
+      "principalOrgId": null,
+      "sourceIp": "192.168.0.1",
+      "user": null,
+      "userAgent": "user-agent",
+      "userArn": null,
+      "clientCert": {
+        "clientCertPem": "CERT_CONTENT",
+        "subjectDN": "www.example.com",
+        "issuerDN": "Example issuer",
+        "serialNumber": "a1:a1:a1:a1:a1:a1:a1:a1:a1:a1:a1:a1:a1:a1:a1:a1",
+        "validity": {
+          "notBefore": "May 28 12:30:02 2019 GMT",
+          "notAfter": "Aug  5 09:36:04 2021 GMT"
+        }
+      }
+    },
+    "path": "/my/path",
+    "protocol": "HTTP/1.1",
+    "requestId": "id=",
+    "requestTime": "04/Mar/2020:19:15:17 +0000",
+    "requestTimeEpoch": 1583349317135,
+    "resourceId": null,
+    "resourcePath": "/my/path",
+    "stage": "$default"
+  },
+  "pathParameters": null,
+  "stageVariables": null,
+  "body": "{\"id\":10876546789,\"description\":\"My order\",\"items\":[{\"id\":1015938732,\"quantity\":1,\"description\":\"item xpto\"}]}",
+  "isBase64Encoded": false
+}

Diff for: examples/snippets/parser/extendAPIGatewaySchema.ts

@@ -0,0 +1,50 @@
+import type { LambdaInterface } from '@aws-lambda-powertools/commons/types';
+import { Logger } from '@aws-lambda-powertools/logger';
+import { parser } from '@aws-lambda-powertools/parser';
+import { APIGatewayProxyEventSchema } from '@aws-lambda-powertools/parser/schemas';
+import type { Context } from 'aws-lambda';
+import { z } from 'zod';
+
+const logger = new Logger();
+
+const orderSchema = z.object({
+  id: z.number().positive(),
+  description: z.string(),
+  items: z.array(
+    z.object({
+      id: z.number().positive(),
+      quantity: z.number(),
+      description: z.string(),
+    })
+  ),
+});
+
+const orderEventSchema = APIGatewayProxyEventSchema.extend({
+  body: z
+    .string()
+    .transform((str, ctx) => {
+      try {
+        return JSON.parse(str); // (1)!
+      } catch (err) {
+        ctx.addIssue({
+          code: 'custom',
+          message: 'Invalid JSON',
+        });
+      }
+    })
+    .pipe(orderSchema), // (2)!
+});
+
+type OrderEvent = z.infer<typeof orderEventSchema>;
+
+class Lambda implements LambdaInterface {
+  @parser({ schema: orderEventSchema })
+  public async handler(event: OrderEvent, _context: Context): Promise<void> {
+    for (const item of event.body.items) {
+      // process OrderItem
+      logger.info('Processing item', { item });
+    }
+  }
+}
+const myFunction = new Lambda();
+export const handler = myFunction.handler.bind(myFunction);