Using LocalStack with AWS SDK v3 - determine options for AWS client constructors.

aws-client-options.js

const DEFAULT_LOCALSTACK_EDGE_PORT = 4566;

/**
 * Get options for use in AWS client constructors.
 *
 * Configure the `AWS_ENDPOINT` environment variable to set an endpoint.
 *
 * ### Example
 *
 * To run tests w/ LocalStack: `AWS_ENDPOINT=http://127.0.0.1:4566 jest`
 *
 * ```js
 * const { DynamoDBClient } = require('@aws-sdk/client-dynamodb');
 *
 * const options = getClientOptions(DynamoDBClient);
 * const client = new DynamoDBClient({
 *  // Add other options here
 *  ...options,
 * });
 * ```
 *
 * To use with LocalStack, you can use the following:
 *
 * ```sh
 * export AWS_ENDPOINT=http://127.0.0.1:4566
 * npm start
 * ```
 *
 * ### Example package.json Commands
 *
 * ```json
 *   "dev": "AWS_ENDPOINT=http://127.0.0.1:4566 terraform apply -auto-approve && npm start",
 *   "test": "AWS_ENDPOINT=http://127.0.0.1:4566 jest",
 * ```
 *
 * ### Note
 *
 * Special detection is done for the S3 client & LocalStack. The 'special' domain `s3.localhost.localstack.cloud` should resolve to `127.0.0.1`.
 * If you are using Minio or other S3-compatible storage, you will need to set `AWS_ENDPOINT` to the correct endpoint & port.
 *
 * @param {*} clientClass An AWS SDK v3 client class.
 */
export default function getClientOptions(clientClass) {
  const endpoint = getEndpoint();
  const isS3Client =
    typeof clientClass === "object" && clientClass.name === "S3Client";

  if (!endpoint) return {};

  if (clientClass === true || isS3Client) {
    const port = endpoint.split(":")[1] || DEFAULT_LOCALSTACK_EDGE_PORT;
    return {
      // If you want to use virtual host addressing of buckets, you can remove `forcePathStyle: true`.
      forcePathStyle: true,
      endpoint: `http://s3.localhost.localstack.cloud:${port}`,
    };
  } else {
    return {
      endpoint: getEndpoint(),
    };
  }
}

function getEndpoint() {
  const { AWS_ENDPOINT: endpoint, LOCALSTACK_HOSTNAME: localStackHostname } =
    process.env;
  if (endpoint) return endpoint;
  if (localStackHostname) return `http://${localStackHostname}:4566`;
  return undefined;
}