@middy/core/executionModeDurableContext.js

🛵 The stylish Node.js middleware engine for AWS Lambda (core package)

// Copyright 2017 - 2026 will Farrell, Luciano Mammino, and Middy contributors.
// SPDX-License-Identifier: MIT
import { withDurableExecution } from "@aws/durable-execution-sdk-js";
import { executionContextKeys, lambdaContextKeys } from "@middy/util";

export const executionModeDurableContext = (
	{ middyRequest, runRequest },
	beforeMiddlewares,
	lambdaHandler,
	afterMiddlewares,
	onErrorMiddlewares,
	plugin,
) => {
	const middy = withDurableExecution(async (event, context) => {
		const request = middyRequest(event, context);
		plugin.requestStart(request);

		// normalize context with executionModeStandard
		// https://docs.aws.amazon.com/lambda/latest/dg/typescript-context.html
		// Idea: Use Proxy instead of copying. Faster for common use case?
		copyKeys(
			request.context,
			request.context.executionContext,
			executionContextKeys,
		);
		copyKeys(request.context, request.context.lambdaContext, lambdaContextKeys);

		// See executionModeStandard for the .cause-chaining rationale.
		let handlerError;
		let response;
		try {
			response = await runRequest(
				request,
				beforeMiddlewares,
				lambdaHandler,
				afterMiddlewares,
				onErrorMiddlewares,
				plugin,
			);
		} catch (err) {
			handlerError = err;
		}
		try {
			await plugin.requestEnd(request);
		} catch (hookErr) {
			if (handlerError) {
				handlerError.cause ??= hookErr;
			} else {
				throw hookErr;
			}
		}
		if (handlerError) throw handlerError;
		return response;
	});
	middy.handler = (replaceLambdaHandler) => {
		lambdaHandler = replaceLambdaHandler;
		return middy;
	};
	return middy;
};

const copyKeys = (to, from, keys) => {
	for (let i = 0, len = keys.length; i < len; i++) {
		to[keys[i]] = from[keys[i]];
	}
};