Powertools for AWS Lambda (TypeScript) - Parser Utility

Powertools for AWS Lambda (TypeScript) is a developer toolkit to implement Serverless best practices and increase developer velocity.

You can use the package in both TypeScript and JavaScript code bases.

• Intro
• Key features
• Usage
  • Middleware
  • Decorator
  • Manual parsing
  • Safe parsing
  • Built-in schemas and envelopes
• Contribute
• Roadmap
• Connect
• How to support Powertools for AWS Lambda (TypeScript)?
  • Becoming a reference customer
  • Sharing your work
  • Using Lambda Layer
• Credits
• License

Intro

The parser utility provides data validation and parsing using Zod, a TypeScript-first schema declaration and validation library.

Key features

• Define data schema as Zod schema, then parse, validate and extract only what you want
• Built-in envelopes to unwrap and validate popular AWS event sources payloads
• Extend and customize envelopes to fit your needs
• Safe parsing option to avoid throwing errors and custom error handling
• Available for Middy.js middleware and TypeScript method decorators

Usage

To get started, install the library by running:

npm install @aws-lambda-powertools/parser zod@~3

Then, define your schema using Zod:

import { z } from 'zod';

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(),
    })
  ),
  optionalField: z.string().optional(),
});

export { orderSchema };

Next, you can parse incoming events using the parser decorator or Middy.js middleware:

Middleware

import type { Context } from 'aws-lambda';
import { parser } from '@aws-lambda-powertools/parser/middleware';
import { z } from 'zod';
import middy from '@middy/core';
import { Logger } from '@aws-lambda-powertools/logger';

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(),
    })
  ),
  optionalField: z.string().optional(),
});

type Order = z.infer<typeof orderSchema>;

const lambdaHandler = async (
  event: Order,
  _context: Context
): Promise<void> => {
  for (const item of event.items) {
    // item is parsed as OrderItem
    logger.info('Processing item', { item });
  }
};

export const handler = middy(lambdaHandler).use(
  parser({ schema: orderSchema })
);

Decorator

import type { Context } from 'aws-lambda';
import type { LambdaInterface } from '@aws-lambda-powertools/commons/types';
import { parser } from '@aws-lambda-powertools/parser';
import { z } from 'zod';
import { Logger } from '@aws-lambda-powertools/logger';

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(),
    })
  ),
  optionalField: z.string().optional(),
});

type Order = z.infer<typeof orderSchema>;

class Lambda implements LambdaInterface {
  @parser({ schema: orderSchema })
  public async handler(event: Order, _context: Context): Promise<void> {
    // event is now typed as Order
    for (const item of event.items) {
      logger.info('Processing item', { item });
    }
  }
}

const myFunction = new Lambda();
export const handler = myFunction.handler.bind(myFunction);

Manual parsing

If you don't want to add an additional dependency, or you prefer the manual approach, you can parse the event directly by calling the parse method on schemas and envelopes:

import type { Context } from 'aws-lambda';
import { z } from 'zod';
import { EventBridgeEnvelope } from '@aws-lambda-powertools/parser/envelopes';
import { EventBridgeSchema } from '@aws-lambda-powertools/parser/schemas';
import type { EventBridgeEvent } from '@aws-lambda-powertools/parser/types';
import { Logger } from '@aws-lambda-powertools/logger';

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(),
    })
  ),
  optionalField: z.string().optional(),
});
type Order = z.infer<typeof orderSchema>;

export const handler = async (
  event: EventBridgeEvent,
  _context: Context
): Promise<void> => {
  const parsedEvent = EventBridgeSchema.parse(event);
  logger.info('Parsed event', parsedEvent);

  const orders: Order = EventBridgeEnvelope.parse(event, orderSchema);
  logger.info('Parsed orders', orders);
};

Safe parsing

When parsing data, you can use the safeParse method to avoid throwing errors and handle them manually:

import type { Context } from 'aws-lambda';
import { parser } from '@aws-lambda-powertools/parser/middleware';
import { z } from 'zod';
import middy from '@middy/core';
import type {
  ParsedResult,
  EventBridgeEvent,
} from '@aws-lambda-powertools/parser/types';
import { Logger } from '@aws-lambda-powertools/logger';

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(),
    })
  ),
  optionalField: z.string().optional(),
});

type Order = z.infer<typeof orderSchema>;

const lambdaHandler = async (
  event: ParsedResult<EventBridgeEvent, Order>,
  _context: Context
): Promise<void> => {
  if (event.success) {
    // (2)!
    for (const item of event.data.items) {
      logger.info('Processing item', { item });
    }
  } else {
    logger.error('Error parsing event', { event: event.error });
    logger.error('Original event', { event: event.originalEvent });
  }
};

export const handler = middy(lambdaHandler).use(
  parser({ schema: orderSchema, safeParse: true })
);

See the safe parsing section in the documentation for more details.

Built-in schemas and envelopes

The utility provides a set of built-in schemas and envelopes to parse popular AWS event sources payloads, for example:

import type { Context } from 'aws-lambda';
import type { LambdaInterface } from '@aws-lambda-powertools/commons/types';
import { parser } from '@aws-lambda-powertools/parser';
import { z } from 'zod';
import { EventBridgeEnvelope } from '@aws-lambda-powertools/parser/envelopes';
import { Logger } from '@aws-lambda-powertools/logger';

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(),
    })
  ),
  optionalField: z.string().optional(),
});

type Order = z.infer<typeof orderSchema>;

class Lambda implements LambdaInterface {
  @parser({ schema: orderSchema, envelope: EventBridgeEnvelope })
  public async handler(event: Order, _context: Context): Promise<void> {
    // event is now typed as Order
    for (const item of event.items) {
      logger.info('Processing item', item); // (2)!
    }
  }
}

const myFunction = new Lambda();
export const handler = myFunction.handler.bind(myFunction);

Check the utility documentation for a complete list of built-in schemas and envelopes.

Contribute

If you are interested in contributing to this project, please refer to our Contributing Guidelines.

Roadmap

The roadmap of Powertools for AWS Lambda (TypeScript) is driven by customers’ demand.
Help us prioritize upcoming functionalities or utilities by upvoting existing RFCs and feature requests, or creating new ones, in this GitHub repository.

Connect

• Powertools for AWS Lambda on Discord: #typescript - Invite link
• Email: [email protected]

How to support Powertools for AWS Lambda (TypeScript)?

Becoming a reference customer

Knowing which companies are using this library is important to help prioritize the project internally. If your company is using Powertools for AWS Lambda (TypeScript), you can request to have your name and logo added to the README file by raising a Support Powertools for AWS Lambda (TypeScript) (become a reference) issue.

The following companies, among others, use Powertools:

• Alma Media
• AppYourself
• Bailey Nelson
• Banxware
• Caylent
• Certible
• Elva
• Flyweight
• globaldatanet
• Hashnode
• LocalStack
• Perfect Post
• Sennder
• tecRacer GmbH & Co. KG
• Trek10
• WeSchool

Sharing your work

Share what you did with Powertools for AWS Lambda (TypeScript) 💞💞. Blog post, workshops, presentation, sample apps and others. Check out what the community has already shared about Powertools for AWS Lambda (TypeScript) here.

Using Lambda Layer

This helps us understand who uses Powertools for AWS Lambda (TypeScript) in a non-intrusive way, and helps us gain future investments for other Powertools for AWS Lambda languages. When using Layers, you can add Powertools as a dev dependency (or as part of your virtual env) to not impact the development process.

Credits

Credits for the Lambda Powertools for AWS Lambda (TypeScript) idea go to DAZN and their DAZN Lambda Powertools.

License

This library is licensed under the MIT-0 License. See the LICENSE file.