fix: resolve region (#560)

* fix: resolve region

Author: Chase Coalwell

Diff for: packages/middleware-location-constraint/src/index.spec.ts

@@ -9,7 +9,7 @@ describe("locationConstrainMiddleware", () => {
 
   it("should remove any CreateBucketConfiguration from requests directed at us-east-1", async () => {
     const handler = locationConstraintMiddleware({
-      region: "us-east-1"
+      region: () => Promise.resolve("us-east-1")
     })(next, {} as any);
     const input = {
       CreateBucketConfiguration: { LocationConstraint: "us-east-1" },
@@ -28,7 +28,7 @@ describe("locationConstrainMiddleware", () => {
 
   it("should apply a CreateBucketConfiguration with a LocationConstraint of the target region for requests directed outside of us-east-1", async () => {
     const handler = locationConstraintMiddleware({
-      region: "us-east-2"
+      region: () => Promise.resolve("us-east-2")
     })(next, {} as any);
     const input = {
       foo: "bar"
@@ -47,7 +47,7 @@ describe("locationConstrainMiddleware", () => {
 
   it("should do nothing if a LocationConstraint had already been set on a request directed outside of us-east-1", async () => {
     const handler = locationConstraintMiddleware({
-      region: "us-east-2"
+      region: () => Promise.resolve("us-east-2")
     })(next, {} as any);
     const input = {
       CreateBucketConfiguration: { LocationConstraint: "us-east-1" },

Diff for: packages/middleware-location-constraint/src/index.ts

@@ -24,6 +24,8 @@ export function locationConstraintMiddleware(
     args: InitializeHandlerArguments<any>
   ): Promise<InitializeHandlerOutput<Output>> => {
     const { CreateBucketConfiguration } = args.input;
+    //After region config resolution, region is a Provider<string>
+    const region = await options.region();
     if (
       !CreateBucketConfiguration ||
       !CreateBucketConfiguration.LocationConstraint
@@ -32,10 +34,10 @@ export function locationConstraintMiddleware(
         ...args,
         input: {
           ...args.input,
-          CreateBucketConfiguration: { LocationConstraint: options.region }
+          CreateBucketConfiguration: { LocationConstraint: region }
         }
       };
-    } else if (options.region === "us-east-1") {
+    } else if (region === "us-east-1") {
       args = {
         ...args,
         input: {