Unreadable error message

[labbedaine]

Hello!

I want to use powertools-lambda-ts in my project but I am facing an issue with capturing the errors when the parsing fails. I would expect an Object that I can use to return to the front-end however I can only access the stack trace. I am sure I am missing something but I don't know what.

logger.error('Error parsing event', { event: event.error });

{
    "level": "ERROR",
    "message": "Error parsing event",
    "sampling_rate": 0,
    "service": "service_undefined",
    "timestamp": "2024-11-25T14:08:34.378Z",
    "xray_trace_id": "1-674484e2-2a74319a3df4a2ac7fef4758",
    "event": {
        "name": "ParseError",
        "location": "/node_modules/.pnpm/@aws-lambda-powertools+parser@2.10.0_@middy+core@6.0.0_zod@3.23.8/node_modules/@aws-lambda-powertools/parser/lib/esm/envelopes/apigw.js:26",
        "message": "Failed to parse ApiGatewayEnvelope body. This error was caused by: Failed to parse envelope. This error was caused by: [\n  {\n    \"code\": \"too_big\",\n    \"maximum\": 2,\n    \"type\": \"string\",\n    \"inclusive\": true,\n    \"exact\": false,\n    \"message\": \"String must contain at most 2 character(s)\",\n    \"path\": [\n      \"firstname\"\n    ]\n  }\n]..",
        "stack": "ParseError: Failed to parse ApiGatewayEnvelope body. This error was caused by: Failed to parse envelope. This error was caused by: [\n  {\n    \"code\": \"too_big\",\n    \"maximum\": 2,\n    \"type\": \"string\",\n    \"inclusive\": true,\n    \"exact\": false,\n    \"message\": \"String must contain at most 2 character(s)\",\n    \"path\": [\n      \"firstname\"\n    ]\n  }\n]..\n    at Object.safeParse (/node_modules/.pnpm/@aws-lambda-powertools+parser@2.10.0_@middy+core@6.0.0_zod@3.23.8/node_modules/@aws-lambda-powertools/parser/lib/esm/envelopes/apigw.js:26:24)\n    at parse (/node_modules/.pnpm/@aws-lambda-powertools+parser@2.10.0_@middy+core@6.0.0_zod@3.23.8/node_modules/@aws-lambda-powertools/parser/lib/esm/parser.js:29:25)\n    at request (/node_modules/.pnpm/@aws-lambda-powertools+parser@2.10.0_@middy+core@6.0.0_zod@3.23.8/node_modules/@aws-lambda-powertools/parser/lib/esm/middleware/parser.js:33:25)\n    at runMiddlewares (/node_modules/.pnpm/@middy+core@6.0.0/node_modules/@middy/core/index.js:229:23)\n    at runRequest (/node_modules/.pnpm/@middy+core@6.0.0/node_modules/@middy/core/index.js:153:11)\n    at Runtime.i (/node_modules/.pnpm/@middy+core@6.0.0/node_modules/@middy/core/index.js:43:12)\n    at Runtime.handleOnceNonStreaming (file:///var/runtime/index.mjs:1173:29)",
        "cause": {
            "name": "ParseError",
            "location": "/node_modules/.pnpm/@aws-lambda-powertools+parser@2.10.0_@middy+core@6.0.0_zod@3.23.8/node_modules/@aws-lambda-powertools/parser/lib/esm/envelopes/envelope.js:50",
            "message": "Failed to parse envelope. This error was caused by: [\n  {\n    \"code\": \"too_big\",\n    \"maximum\": 2,\n    \"type\": \"string\",\n    \"inclusive\": true,\n    \"exact\": false,\n    \"message\": \"String must contain at most 2 character(s)\",\n    \"path\": [\n      \"firstname\"\n    ]\n  }\n].",
            "stack": "ParseError: Failed to parse envelope. This error was caused by: [\n  {\n    \"code\": \"too_big\",\n    \"maximum\": 2,\n    \"type\": \"string\",\n    \"inclusive\": true,\n    \"exact\": false,\n    \"message\": \"String must contain at most 2 character(s)\",\n    \"path\": [\n      \"firstname\"\n    ]\n  }\n].\n    at Object.safeParse (/node_modules/.pnpm/@aws-lambda-powertools+parser@2.10.0_@middy+core@6.0.0_zod@3.23.8/node_modules/@aws-lambda-powertools/parser/lib/esm/envelopes/envelope.js:50:28)\n    at Object.safeParse (/node_modules/.pnpm/@aws-lambda-powertools+parser@2.10.0_@middy+core@6.0.0_zod@3.23.8/node_modules/@aws-lambda-powertools/parser/lib/esm/envelopes/apigw.js:22:37)\n    at parse (/node_modules/.pnpm/@aws-lambda-powertools+parser@2.10.0_@middy+core@6.0.0_zod@3.23.8/node_modules/@aws-lambda-powertools/parser/lib/esm/parser.js:29:25)\n    at request (/node_modules/.pnpm/@aws-lambda-powertools+parser@2.10.0_@middy+core@6.0.0_zod@3.23.8/node_modules/@aws-lambda-powertools/parser/lib/esm/middleware/parser.js:33:25)\n    at runMiddlewares (/node_modules/.pnpm/@middy+core@6.0.0/node_modules/@middy/core/index.js:229:23)\n    at runRequest (/node_modules/.pnpm/@middy+core@6.0.0/node_modules/@middy/core/index.js:153:11)\n    at Runtime.i (/node_modules/.pnpm/@middy+core@6.0.0/node_modules/@middy/core/index.js:43:12)\n    at Runtime.handleOnceNonStreaming (file:///var/runtime/index.mjs:1173:29)",
            "cause": {
                "name": "ZodError",
                "location": "/node_modules/.pnpm/zod@3.23.8/node_modules/zod/lib/index.mjs:587",
                "message": "[\n  {\n    \"code\": \"too_big\",\n    \"maximum\": 2,\n    \"type\": \"string\",\n    \"inclusive\": true,\n    \"exact\": false,\n    \"message\": \"String must contain at most 2 character(s)\",\n    \"path\": [\n      \"firstname\"\n    ]\n  }\n]",
                "stack": "ZodError: [\n  {\n    \"code\": \"too_big\",\n    \"maximum\": 2,\n    \"type\": \"string\",\n    \"inclusive\": true,\n    \"exact\": false,\n    \"message\": \"String must contain at most 2 character(s)\",\n    \"path\": [\n      \"firstname\"\n    ]\n  }\n]\n    at Object.get error (/node_modules/.pnpm/zod@3.23.8/node_modules/zod/lib/index.mjs:587:31)\n    at Object.safeParse (/node_modules/.pnpm/@aws-lambda-powertools+parser@2.10.0_@middy+core@6.0.0_zod@3.23.8/node_modules/@aws-lambda-powertools/parser/lib/esm/envelopes/envelope.js:51:39)\n    at Object.safeParse (/node_modules/.pnpm/@aws-lambda-powertools+parser@2.10.0_@middy+core@6.0.0_zod@3.23.8/node_modules/@aws-lambda-powertools/parser/lib/esm/envelopes/apigw.js:22:37)\n    at parse (/node_modules/.pnpm/@aws-lambda-powertools+parser@2.10.0_@middy+core@6.0.0_zod@3.23.8/node_modules/@aws-lambda-powertools/parser/lib/esm/parser.js:29:25)\n    at request (/node_modules/.pnpm/@aws-lambda-powertools+parser@2.10.0_@middy+core@6.0.0_zod@3.23.8/node_modules/@aws-lambda-powertools/parser/lib/esm/middleware/parser.js:33:25)\n    at runMiddlewares (/node_modules/.pnpm/@middy+core@6.0.0/node_modules/@middy/core/index.js:229:23)\n    at runRequest (/node_modules/.pnpm/@middy+core@6.0.0/node_modules/@middy/core/index.js:153:11)\n    at Runtime.i (/node_modules/.pnpm/@middy+core@6.0.0/node_modules/@middy/core/index.js:43:12)\n    at Runtime.handleOnceNonStreaming (file:///var/runtime/index.mjs:1173:29)"
            }
        }
    }
}

Thanks for the support!

[dreamorosi]

Hi, thank you for opening this discussion.

The log you're seeing is the formatted version of the error. When you log an error using Logger, its key get formatted into a JSON-serializable object, which includes the stack trace.

At runtime, both event.error and event.error.cause are indeed errors and instances of respectively ParseError & ZodError which you can work with.

You can verify that this is the case with code similar to this:

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

const logger = new Logger({ logLevel: 'debug' });

export const handler = middy()
  .use(
    parser({
      schema: z.object({
        foo: z.string(),
      }),
      safeParse: true,
    })
  )
  .handler(async (event) => {
    if (event.success === false) {
      logger.debug('event.error instanceof ParseError', {
        instanceOf: event.error instanceof ParseError,
      });
      logger.debug('event.error.cause instanceof ZodError', {
        instanceOf: event.error.cause instanceof ZodError,
      });
    }

    return {
      statusCode: 200,
      body: JSON.stringify('Hello, World!'),
    };
  });

which will log these two debug logs (notice the instanceOf field is true in both cases):

{"level":"DEBUG","message":"event.error instanceof ParseError","sampling_rate":0,"service":"service_undefined","timestamp":"2024-11-25T19:39:23.866Z","instanceOf":true}
{"level":"DEBUG","message":"event.error.cause instanceof ZodError","sampling_rate":0,"service":"service_undefined","timestamp":"2024-11-25T19:39:23.867Z","instanceOf":true}