feat(batch): make parser dependencies optional with Standard Schema support

Author: dreamorosi

package-lock.json

@@ -81,10 +81,12 @@
     "nodejs"
   ],
   "dependencies": {
-    "@aws-lambda-powertools/commons": "2.26.1"
+    "@aws-lambda-powertools/commons": "2.26.1",
+    "@standard-schema/spec": "^1.0.0"
   },
   "devDependencies": {
+    "@aws-lambda-powertools/parser": "2.26.1",
     "@aws-lambda-powertools/testing-utils": "file:../testing",
-    "@aws-lambda-powertools/parser": "2.26.1"
+    "zod": "^4.1.8"
   }
 }

packages/batch/package.json

@@ -1,13 +1,21 @@
 import type { GenericLogger } from '@aws-lambda-powertools/commons/types';
 import type { StandardSchemaV1 } from '@standard-schema/spec';
-import type { ZodType } from 'zod';
 import { EventType, SchemaVendor } from './constants.js';
 import { ParsingError } from './errors.js';
 import type {
   BasePartialBatchProcessorParserConfig,
   EventSourceDataClassTypes,
+  RuntimeZodType,
 } from './types.js';
 
+/**
+ * Type guard to check if the schema is a Zod schema
+ *
+ * @param schema - The schema to check
+ */
+const isZodSchema = (schema: StandardSchemaV1): schema is RuntimeZodType =>
+  schema['~standard'].vendor === SchemaVendor.Zod;
+
 /**
  * Extend the schema according to the event type passed.
  *
@@ -22,7 +30,7 @@ import type {
  */
 const createExtendedSchema = async (options: {
   eventType: keyof typeof EventType;
-  innerSchema: ZodType;
+  innerSchema: RuntimeZodType;
   transformer?: BasePartialBatchProcessorParserConfig['transformer'];
 }) => {
   const { eventType, innerSchema, transformer } = options;
@@ -73,8 +81,8 @@ const createExtendedSchema = async (options: {
   );
   return DynamoDBStreamRecord.extend({
     dynamodb: DynamoDBStreamChangeRecordBase.extend({
-      OldImage: schema.optional(),
-      NewImage: schema.optional(),
+      OldImage: schema,
+      NewImage: schema,
     }),
   });
 };
@@ -131,7 +139,7 @@ const parser = async (
   }
   if (innerSchema) {
     // Only proceed with schema extension if it's a Zod schema
-    if (innerSchema['~standard'].vendor !== SchemaVendor.Zod) {
+    if (!isZodSchema(innerSchema)) {
       logger.error(
         'The schema provided is not supported. Only Zod schemas are supported for extension.'
       );

packages/batch/src/parser.ts

@@ -7,7 +7,6 @@ import type {
   SQSRecord,
   StreamRecord,
 } from 'aws-lambda';
-import type { ZodType } from 'zod';
 import type { BasePartialBatchProcessor } from './BasePartialBatchProcessor.js';
 import type { BatchProcessor } from './BatchProcessor.js';
 import type { parser } from './parser.js';
@@ -144,8 +143,12 @@ type BasePartialBatchProcessorParserConfig =
       schema?: never;
       /**
        * Payload-only Zod schema, mutually exclusive with `schema`
+       *
+       * @remarks
+       * Only Zod schemas are supported for `innerSchema` as we rely on Zod's schema extension capabilities.
+       * If you need to use a different Standard Schema-compatible library, use `schema` instead.
        */
-      innerSchema: ZodType;
+      innerSchema: StandardSchemaV1;
       /**
        * Payload transformer, only available with `innerSchema`
        */
@@ -239,6 +242,20 @@ type ParsedRecord<TRecord, TPayload, TOldPayload = TPayload> = TRecord extends {
         }
       : TRecord;
 
+/**
+ * Type representing a Zod schema at runtime.
+ *
+ * Parts of the parser integration within BatchProcessor rely on Zod for schema transformations,
+ * however some other parts also support other Standard Schema-compatible libraries.
+ *
+ * To avoid forcing a direct dependency on Zod, we use `any` here, which is not ideal but necessary.
+ *
+ * The vendor is checked at runtime to ensure Zod is being used when required using `StandardSchemaV1['~standard'].vendor`.
+ *
+ * biome-ignore lint/suspicious/noExplicitAny: using `any` to avoid direct dependency on 'zod'
+ */
+type RuntimeZodType = any;
+
 export type {
   BatchProcessingOptions,
   BaseRecord,
@@ -249,4 +266,5 @@ export type {
   PartialItemFailureResponse,
   BasePartialBatchProcessorParserConfig,
   ParsedRecord,
+  RuntimeZodType,
 };