Make OperationSpec.baseUrl an optional property for moving OperationSpecs into module/file scope

lib/operationSpec.ts

@@ -22,9 +22,10 @@ export interface OperationSpec {
 
   /**
    * The URL that was provided in the service's specification. This will still have all of the URL
-   * template variables in it.
+   * template variables in it. If this is not provided when the OperationSpec is created, then it
+   * will be populated by a "baseUri" property on the ServiceClient.
    */
-  baseUrl: string;
+  baseUrl?: string;
 
   /**
    * The fixed path for this operation's URL. This will still have all of the URL template variables

lib/serviceClient.ts

@@ -177,6 +177,13 @@ export class ServiceClient {
 
     let result: Promise<HttpOperationResponse>;
     try {
+      if (operationSpec.baseUrl == undefined) {
+        operationSpec.baseUrl = (this as any).baseUri;
+        if (!operationSpec.baseUrl) {
+          throw new Error("If operationSpec.baseUrl is not specified, then the ServiceClient must have a baseUri string property that contains the base URL to use.");
+        }
+      }
+
       httpRequest.method = operationSpec.httpMethod;
       httpRequest.operationSpec = operationSpec;