Export types with export type (#1284)

* Export types with `export type`

* Fix linter error

* Also export ServiceExceptionOptions as type

Author: libre-man

smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/CommandGenerator.java

@@ -384,7 +384,8 @@ private void generateCommandMiddlewareResolver(String configType) {
 
     private void addInputAndOutputTypes() {
         writer.writeDocs("@public");
-        writer.write("export { __MetadataBearer, $$Command };");
+        writer.write("export type { __MetadataBearer };");
+        writer.write("export { $$Command };");
 
         writeInputType(inputType.getName(), operationIndex.getInput(operation), symbol.getName());
         writeOutputType(outputType.getName(), operationIndex.getOutput(operation), symbol.getName());

smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/IndexGenerator.java

@@ -114,8 +114,11 @@ private static void writeClientExports(
         }
 
         // Export Runtime Extension and Client ExtensionConfiguration interfaces
-        writer.write("export { RuntimeExtension } from \"./runtimeExtensions\";");
-        writer.write("export { $LExtensionConfiguration } from \"./extensionConfiguration\";", normalizedClientName);
+        writer.write("export type { RuntimeExtension } from \"./runtimeExtensions\";");
+        writer.write(
+            "export type { $LExtensionConfiguration } from \"./extensionConfiguration\";",
+            normalizedClientName
+        );
 
         // Write export statement for commands.
         writer.write("export * from \"./commands\";");

smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/integration/AddBaseServiceExceptionClass.java

@@ -69,7 +69,8 @@ private void writeAdditionalFiles(
                                     TypeScriptDependency.AWS_SMITHY_CLIENT);
                             // Export ServiceException information to allow
                             //      documentation inheritance to consume their types
-                            writer.write("export { __ServiceException, __ServiceExceptionOptions }\n");
+                            writer.write("export type { __ServiceExceptionOptions }\n");
+                            writer.write("export { __ServiceException }\n");
                             writer.writeDocs("@public\n\nBase exception class for all service exceptions from "
                                     + serviceName + " service.");
                             writer.openBlock("export class $L extends __ServiceException {", serviceExceptionName);