fix: respect hostname immutability in endpoints to disable host prefixing (#612)

Author: ianbotsf

runtime/protocol/http/common/src/aws/smithy/kotlin/runtime/http/middleware/ResolveEndpoint.kt

@@ -31,7 +31,12 @@ class ResolveEndpoint(
 @InternalApi
 fun setRequestEndpoint(req: SdkHttpRequest, endpoint: Endpoint) {
     val hostPrefix = req.context.getOrNull(HttpOperationContext.HostPrefix)
-    val hostname = if (hostPrefix != null) "${hostPrefix}${endpoint.uri.host}" else endpoint.uri.host
+    val hostname = if (hostPrefix != null && !endpoint.isHostnameImmutable) {
+        "$hostPrefix${endpoint.uri.host}"
+    } else {
+        endpoint.uri.host
+    }
+
     req.subject.url.scheme = endpoint.uri.scheme
     req.subject.url.host = hostname
     req.subject.url.port = endpoint.uri.port

runtime/protocol/http/common/test/aws/smithy/kotlin/runtime/http/middleware/ResolveEndpointTest.kt

@@ -100,6 +100,22 @@ class ResolveEndpointTest {
         assertEquals("/operation", actual.url.path)
     }
 
+    @Test
+    fun testSkipHostPrefixForImmutableHostnames() = runTest {
+        val op = newTestOperation<Unit, Unit>(HttpRequestBuilder().apply { url.path = "/operation" }, Unit)
+        val endpoint = Endpoint(uri = Url.parse("http://api.test.com"), isHostnameImmutable = true)
+        val resolver = EndpointResolver { endpoint }
+        op.install(ResolveEndpoint(resolver))
+        op.context[HttpOperationContext.HostPrefix] = "prefix."
+
+        op.roundTrip(client, Unit)
+        val actual = op.context[HttpOperationContext.HttpCallList].first().request
+
+        assertEquals("api.test.com", actual.url.host)
+        assertEquals(Protocol.HTTP, actual.url.scheme)
+        assertEquals("/operation", actual.url.path)
+    }
+
     @Test
     fun testEndpointPathPrefixWithNonEmptyPath() = runTest {
         val op = newTestOperation<Unit, Unit>(HttpRequestBuilder().apply { url.path = "/operation" }, Unit)