fix(aws): honour AWS_ENDPOINT_URL for aws4fetch-based resources

alchemy/src/aws/control/client.ts

@@ -3,6 +3,7 @@ import { loadConfig } from "@smithy/node-config-provider";
 import { AwsClient } from "aws4fetch";
 import { logger } from "../../util/logger.ts";
 import { safeFetch } from "../../util/safe-fetch.ts";
+import { awsEndpoint } from "../utils.ts";
 import {
   AlreadyExistsError,
   CloudControlError,
@@ -355,7 +356,7 @@ export class CloudControlClient {
     while (true) {
       try {
         const args = [
-          `https://cloudcontrolapi.${this.region}.amazonaws.com/?Action=${action}&Version=2021-09-30`,
+          `${awsEndpoint("cloudcontrolapi", this.region)}/?Action=${action}&Version=2021-09-30`,
           {
             method: "POST",
             headers: {

alchemy/src/aws/ec2/utils.ts

@@ -6,7 +6,7 @@ import { logger } from "../../util/logger.ts";
 import { flattenParams } from "../../util/params.ts";
 import type { AwsClientProps } from "../client-props.ts";
 import { resolveAwsCredentials } from "../credentials.ts";
-import { getRegion } from "../utils.ts";
+import { awsEndpoint, getRegion } from "../utils.ts";
 
 /**
  * Shared EC2 utilities for all EC2 resources
@@ -100,8 +100,10 @@ export async function callEC2Api<T>(
   // Try the API call, and retry once with fresh credentials on auth failure
   for (let attempt = 1; attempt <= 2; attempt++) {
     try {
-      // Use the client's region instead of the global region
-      const url = `https://ec2.${client.region}.amazonaws.com/`;
+      // Use the client's region instead of the global region.
+      // Honour AWS_ENDPOINT_URL / AWS_ENDPOINT_URL_EC2 for emulators
+      // (LocalStack, moto, etc.) — matches AWS SDK v3 behaviour.
+      const url = `${awsEndpoint("ec2", client.region ?? "us-east-1")}/`;
 
       const body = new URLSearchParams({
         Action: action,

alchemy/src/aws/utils.ts

@@ -14,13 +14,29 @@ export const getRegion: Provider<string> = loadConfig({
   default: "us-east-1",
 });
 
+/**
+ * Resolve the endpoint URL for an aws4fetch service request, honouring the
+ * same `AWS_ENDPOINT_URL_<SERVICE>` / `AWS_ENDPOINT_URL` env vars as the AWS
+ * SDK / CLI so aws4fetch-based resources can be pointed at LocalStack, moto,
+ * or any other emulator.
+ */
+export function awsEndpoint(service: string, region: string): string {
+  return (
+    process.env[
+      `AWS_ENDPOINT_URL_${service.toUpperCase().replace(/-/g, "_")}`
+    ] ??
+    process.env.AWS_ENDPOINT_URL ??
+    `https://${service}.${region}.amazonaws.com`
+  ).replace(/\/+$/, "");
+}
+
 /**
  * AWS Service Configuration
  */
 export interface AwsServiceConfig {
   service: string;
   version: string;
-  endpoint: (region: string) => string;
+  endpoint?: (region: string) => string;
 }
 
 /**
@@ -63,7 +79,9 @@ export function getAwsApiCaller<T = any>(
       for (let attempt = 1; attempt <= 2; attempt++) {
         try {
           const region = await getRegion();
-          const url = config.endpoint(region);
+          const url = config.endpoint
+            ? config.endpoint(region)
+            : `${awsEndpoint(config.service, region)}/`;
 
           const body = new URLSearchParams({
             Action: action,