From e87f2b3c416b5d8a61e4f451a74c8b473c2dfa5e Mon Sep 17 00:00:00 2001
From: sid <48153483+siddsriv@users.noreply.github.com>
Date: Mon, 13 Jan 2025 15:19:18 -0500
Subject: [PATCH] fix(smithy-client): add prototype chain fallback for service
 exception (#1503)

* fix(smithy-client): add prototype chain fallback for service exception

* chore: changeset

* chore: move to isInstance

* test(smithy-client): add test case for different class name and name prop

* chore: formatting

* test(smithy-client): update test for ClientServiceException
---
 .changeset/rich-emus-cry.md                   |  5 +++++
 packages/smithy-client/src/exceptions.spec.ts | 11 +++++++++++
 packages/smithy-client/src/exceptions.ts      |  7 ++++---
 3 files changed, 20 insertions(+), 3 deletions(-)
 create mode 100644 .changeset/rich-emus-cry.md

diff --git a/.changeset/rich-emus-cry.md b/.changeset/rich-emus-cry.md
new file mode 100644
index 00000000000..8d7e2cf98de
--- /dev/null
+++ b/.changeset/rich-emus-cry.md
@@ -0,0 +1,5 @@
+---
+"@smithy/smithy-client": patch
+---
+
+prototype chain fallback for service exception
diff --git a/packages/smithy-client/src/exceptions.spec.ts b/packages/smithy-client/src/exceptions.spec.ts
index 6d3ee8989d3..e0f23aeaa8b 100644
--- a/packages/smithy-client/src/exceptions.spec.ts
+++ b/packages/smithy-client/src/exceptions.spec.ts
@@ -97,6 +97,17 @@ describe("Exception Hierarchy Tests", () => {
       expect(clientException instanceof ClientServiceException).toBe(true);
       expect(clientException instanceof ModeledClientServiceException).toBe(false);
     });
+
+    it("should handle exceptions where name indicates error type", () => {
+      const egError = new ClientServiceException();
+      egError.name = "EgTooLarge"; // specific error type name
+      // Should maintain instanceof chain
+      expect(egError instanceof Error).toBe(true);
+      expect(egError instanceof ServiceException).toBe(true);
+      expect(egError instanceof ClientServiceException).toBe(true);
+      // The name property can be used to identify specific error types
+      expect(egError.name).toBe("EgTooLarge");
+    });
   });
 
   describe("ModeledClientServiceException Instance Tests", () => {
diff --git a/packages/smithy-client/src/exceptions.ts b/packages/smithy-client/src/exceptions.ts
index 35417a8b688..b0878bb52fa 100644
--- a/packages/smithy-client/src/exceptions.ts
+++ b/packages/smithy-client/src/exceptions.ts
@@ -45,9 +45,10 @@ export class ServiceException extends Error implements SmithyException, Metadata
     if (!value) return false;
     const candidate = value as ServiceException;
     return (
-      Boolean(candidate.$fault) &&
-      Boolean(candidate.$metadata) &&
-      (candidate.$fault === "client" || candidate.$fault === "server")
+      ServiceException.prototype.isPrototypeOf(candidate) ||
+      (Boolean(candidate.$fault) &&
+        Boolean(candidate.$metadata) &&
+        (candidate.$fault === "client" || candidate.$fault === "server"))
     );
   }