moves host prefix addition to a build step middleware

codegen/smithy-go-codegen/src/main/java/software/amazon/smithy/go/codegen/SmithyGoDependency.java

@@ -110,6 +110,6 @@ private static GoDependency relativePackage(
     private static final class Versions {
         private static final String GO_STDLIB = "1.14";
         private static final String GO_CMP = "v0.4.1";
-        private static final String SMITHY_GO = "v0.3.1-0.20201104233911-38864709e183";
+        private static final String SMITHY_GO = "v0.3.1-0.20201108010311-62c2a93810b4";
     }
 }

codegen/smithy-go-codegen/src/main/java/software/amazon/smithy/go/codegen/integration/EndpointHostPrefixMiddleware.java

@@ -35,6 +35,10 @@
 import software.amazon.smithy.model.shapes.StructureShape;
 import software.amazon.smithy.model.traits.EndpointTrait;
 
+/**
+ * EndpointHostPrefixMiddleware adds middlewares to identify
+ * a host prefix and mutate the request URL host if permitted.
+**/
 public class EndpointHostPrefixMiddleware implements GoIntegration {
 
     private static final MiddlewareIdentifier MIDDLEWARE_ID = MiddlewareIdentifier.string("EndpointHostPrefix");
@@ -84,10 +88,9 @@ public void writeAdditionalFiles(
                         middlewareHelperName,
                         () -> {
                             writer.write(
-                                    "return stack.Serialize.Insert(&$L{}, `OperationSerializer`, middleware.Before)",
+                                    "return stack.Serialize.Insert(&$L{}, `OperationSerializer`, middleware.After)",
                                     middlewareName);
                         });
-
             });
         });
     }
@@ -109,7 +112,8 @@ private static void writeMiddleware(
             writer.addUseImports(SmithyGoDependency.SMITHY_HTTP_TRANSPORT);
             writer.addUseImports(SmithyGoDependency.FMT);
 
-            w.openBlock("if smithyhttp.GetHostnameImmutable(ctx) {", "}", () -> {
+            w.openBlock("if smithyhttp.GetHostnameImmutable(ctx) || "
+                    + "smithyhttp.IsEndpointHostPrefixDisabled(ctx) {", "}", () -> {
                 w.write("return next.$L(ctx, in)", generator.getHandleMethodName());
             }).write("");
 
@@ -119,8 +123,7 @@ private static void writeMiddleware(
             }).write("");
 
             if (pattern.getLabels().isEmpty()) {
-                w.write("req.HostPrefix = $S", pattern.toString());
-
+                w.write("req.URL.Host = $S + req.URL.Host", pattern.toString());
             } else {
                 // If the pattern has labels, we need to build up the host prefix using a string builder.
                 writer.addUseImports(SmithyGoDependency.STRINGS);
@@ -156,8 +159,7 @@ private static void writeMiddleware(
                         });
                     }
                 }
-
-                w.write("req.HostPrefix = prefix.String()");
+                w.write("req.URL.Host = prefix.String() + req.URL.Host");
             }
             w.write("");
 

transport/http/middleware_metadata.go

@@ -4,6 +4,7 @@ import "context"
 
 type (
 	hostnameImmutableKey struct{}
+	hostPrefixDisableKey struct{}
 )
 
 // GetHostnameImmutable retrieves if the endpoint hostname should be considered
@@ -18,3 +19,17 @@ func GetHostnameImmutable(ctx context.Context) (v bool) {
 func SetHostnameImmutable(ctx context.Context, value bool) context.Context {
 	return context.WithValue(ctx, hostnameImmutableKey{}, value)
 }
+
+// DisableEndpointHostPrefix sets or modifies if the request's endpoint host
+// prefixing to be disabled. If value is set to true, endpoint host prefixing
+// will be disabled.
+func DisableEndpointHostPrefix(ctx context.Context, value bool) context.Context {
+	return context.WithValue(ctx, hostPrefixDisableKey{}, value)
+}
+
+// IsEndpointHostPrefixDisabled retrieves if the hostname prefixing
+//  is disabled.
+func IsEndpointHostPrefixDisabled(ctx context.Context) (v bool) {
+	v, _ = ctx.Value(hostPrefixDisableKey{}).(bool)
+	return v
+}

transport/http/request.go

@@ -18,7 +18,6 @@ type Request struct {
 	stream           io.Reader
 	isStreamSeekable bool
 	streamStartPos   int64
-	HostPrefix       string
 }
 
 // NewStackRequest returns an initialized request ready to populated with the
@@ -127,7 +126,7 @@ func (r *Request) SetStream(reader io.Reader) (rc *Request, err error) {
 
 // Build returns a build standard HTTP request value from the Smithy request.
 // The request's stream is wrapped in a safe container that allows it to be
-// reused for subsiquent attempts.
+// reused for subsequent attempts.
 func (r *Request) Build(ctx context.Context) *http.Request {
 	req := r.Request.Clone(ctx)
 
@@ -139,11 +138,6 @@ func (r *Request) Build(ctx context.Context) *http.Request {
 		req.ContentLength = 0
 	}
 
-	// Add the host prefix
-	if len(r.HostPrefix) != 0 {
-		req.URL.Host = r.HostPrefix + req.URL.Host
-	}
-
 	return req
 }