Skip avoidable conversion in CredentialsUtils (#3878)

Author: gosar

core/auth/src/main/java/software/amazon/awssdk/auth/credentials/CredentialUtils.java

@@ -97,6 +97,9 @@ public static AwsCredentialsProvider toCredentialsProvider(
         if (identityProvider == null) {
             return null;
         }
+        if (identityProvider instanceof AwsCredentialsProvider) {
+            return (AwsCredentialsProvider) identityProvider;
+        }
         return () -> {
             // TODO: Exception handling for CompletionException thrown from join?
             AwsCredentialsIdentity awsCredentialsIdentity = identityProvider.resolveIdentity().join();

core/auth/src/test/java/software/amazon/awssdk/auth/credentials/CredentialUtilsTest.java

@@ -20,6 +20,7 @@
 import org.junit.jupiter.api.Test;
 import software.amazon.awssdk.identity.spi.AwsCredentialsIdentity;
 import software.amazon.awssdk.identity.spi.AwsSessionCredentialsIdentity;
+import software.amazon.awssdk.identity.spi.IdentityProvider;
 
 public class CredentialUtilsTest {
 
@@ -83,7 +84,7 @@ public String sessionToken() {
     }
 
     @Test
-    public void toCredentials_AwsCredentials_doesNotCreateNewObject() {
+    public void toCredentials_AwsCredentials_returnsAsIs() {
         AwsCredentialsIdentity input = AwsBasicCredentials.create("ak", "sk");
         AwsCredentials output = CredentialUtils.toCredentials(input);
         assertThat(output).isSameAs(input);
@@ -130,6 +131,14 @@ public void toCredentialsProvider_null_returnsNull() {
         assertThat(CredentialUtils.toCredentialsProvider(null)).isNull();
     }
 
+    @Test
+    public void toCredentialsProvider_AwsCredentialsProvider_returnsAsIs() {
+        IdentityProvider<AwsCredentialsIdentity> input =
+            StaticCredentialsProvider.create(AwsBasicCredentials.create("akid", "skid"));
+        AwsCredentialsProvider output = CredentialUtils.toCredentialsProvider(input);
+        assertThat(output).isSameAs(input);
+    }
+
     @Test
     public void toCredentialsProvider_IdentityProvider_converts() {
         AwsCredentialsProvider credentialsProvider = CredentialUtils.toCredentialsProvider(