fix: propagate the configured region to the S3 client (#600)

* fix: propagate the configured region to the S3 client and test if the region is actually propagated

src/main/java/software/amazon/nio/spi/s3/S3ClientProvider.java

@@ -8,6 +8,7 @@
 import com.github.benmanes.caffeine.cache.Cache;
 import com.github.benmanes.caffeine.cache.Caffeine;
 import java.time.Duration;
+import software.amazon.awssdk.regions.Region;
 import software.amazon.awssdk.services.s3.S3AsyncClient;
 import software.amazon.awssdk.services.s3.S3CrtAsyncClientBuilder;
 import software.amazon.nio.spi.s3.config.S3NioSpiConfiguration;
@@ -79,6 +80,11 @@ S3CrtAsyncClientBuilder configureCrtClient() {
             asyncClientBuilder.credentialsProvider(() -> credentials);
         }
 
+        var region = configuration.getRegion();
+        if (region != null) {
+            asyncClientBuilder.region(Region.of(region));
+        }
+
         return asyncClientBuilder.forcePathStyle(configuration.getForcePathStyle());
     }
 

src/test/java/software/amazon/nio/spi/s3/S3ClientProviderTest.java

@@ -18,7 +18,9 @@
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.mockito.junit.jupiter.MockitoExtension;
+import software.amazon.awssdk.regions.Region;
 import software.amazon.awssdk.services.s3.S3AsyncClient;
+import software.amazon.awssdk.services.s3.S3ServiceClientConfiguration;
 import software.amazon.nio.spi.s3.config.S3NioSpiConfiguration;
 
 @ExtendWith(MockitoExtension.class)
@@ -77,6 +79,26 @@ public void testClosedClientIsNotReused() {
         assertNotSame(s3Client, s3Client2);
     }
 
+    @Test
+    public void testRegionIsPropagated() {
+        // expect a non-standard region
+        final var expectedRegion = Region.AP_SOUTHEAST_2;
+
+        // set it in the provider
+        provider.configuration.withRegion(expectedRegion.id());
+
+        try (final var s3Client = provider.generateClient("test-bucket")) {
+            // get the actual one from the created client
+            assertNotNull(s3Client);
+            final var configuration = s3Client.serviceClientConfiguration();
+            assertNotNull(configuration);
+            final var actualRegion = configuration.region();
+
+            // assert it is as expected
+            assertSame(expectedRegion, actualRegion);
+        }
+    }
+
     @Test
     public void generateAsyncClientByEndpointBucketCredentials() {
         // GIVEN