add support for error cause in transient error checks

.changeset/good-dots-run.md

@@ -0,0 +1,6 @@
+---
+"@smithy/service-error-classification": patch
+"@smithy/types": patch
+---
+
+add support for error cause in transient error checks

packages/service-error-classification/src/index.spec.ts

@@ -15,14 +15,16 @@ const checkForErrorType = (
     name?: string;
     httpStatusCode?: number;
     $retryable?: RetryableTrait;
+    cause?: Partial<Error>;
   },
   errorTypeResult: boolean
 ) => {
-  const { name, httpStatusCode, $retryable } = options;
+  const { name, httpStatusCode, $retryable, cause } = options;
   const error = Object.assign(new Error(), {
     name,
     $metadata: { httpStatusCode },
     $retryable,
+    cause,
   });
   expect(isErrorTypeFunc(error as SdkError)).toBe(errorTypeResult);
 };
@@ -127,6 +129,18 @@ describe("isTransientError", () => {
       break;
     }
   }
+
+  TRANSIENT_ERROR_CODES.forEach((name) => {
+    it(`should declare error with cause with the name "${name}" to be a Transient error`, () => {
+      checkForErrorType(isTransientError, { cause: { name } }, true);
+    });
+  });
+
+  it("should limit recursion to 10 depth", () => {
+    const error = { cause: null } as SdkError;
+    error.cause = error;
+    checkForErrorType(isTransientError, { cause: error }, false);
+  });
 });
 
 describe("isServerError", () => {

packages/service-error-classification/src/index.ts

@@ -31,11 +31,12 @@ export const isThrottlingError = (error: SdkError) =>
  * cause where the NodeHttpHandler does not decorate the Error with
  * the name "TimeoutError" to be checked by the TRANSIENT_ERROR_CODES condition.
  */
-export const isTransientError = (error: SdkError) =>
+export const isTransientError = (error: SdkError, depth = 0): boolean =>
   isClockSkewCorrectedError(error) ||
   TRANSIENT_ERROR_CODES.includes(error.name) ||
   NODEJS_TIMEOUT_ERROR_CODES.includes((error as { code?: string })?.code || "") ||
-  TRANSIENT_ERROR_STATUS_CODES.includes(error.$metadata?.httpStatusCode || 0);
+  TRANSIENT_ERROR_STATUS_CODES.includes(error.$metadata?.httpStatusCode || 0) ||
+  (error.cause !== undefined && depth <= 10 && isTransientError(error.cause, depth + 1));
 
 export const isServerError = (error: SdkError) => {
   if (error.$metadata?.httpStatusCode !== undefined) {

packages/types/src/shapes.ts

@@ -90,4 +90,5 @@ export type SdkError = Error &
        */
       readonly clockSkewCorrected?: true;
     };
+    cause?: Error;
   };