fix(smithy-client): decorateServiceException not to overwrite modeled members

Author: AllanZhengYP

packages/smithy-client/src/exceptions.spec.ts

@@ -29,6 +29,11 @@ describe("decorateServiceException", () => {
     expect(decorated.message).toBe("Error");
   });
 
+  it("should not overwrite the parsed exceptions", () => {
+    const decorated = decorateServiceException(exception, { message: "Another Error" });
+    expect(decorated.message).toBe("Error");
+  });
+
   it("should replace Message with message", () => {
     const decorated = decorateServiceException({
       name: "Error",

packages/smithy-client/src/exceptions.ts

@@ -49,8 +49,11 @@ export const decorateServiceException = <E extends ServiceException>(
   Object.entries(additions)
     .filter(([, v]) => v !== undefined)
     .forEach(([k, v]) => {
-      // @ts-ignore assign unmodeled keys
-      exception[k] = v;
+      // @ts-ignore examine unmodeled keys
+      if (exception[k] == undefined || exception[k] === "") {
+        // @ts-ignore assign unmodeled keys
+        exception[k] = v;
+      }
     });
   // load error message from possible locations
   // @ts-expect-error message could exist in Message key.