Address review feedback on StatusRuntimeExceptionHelper

1. Null-safe description: getDescriptionOrDefault() returns "(no description)"
   instead of letting null propagate into error messages.
2. Javadoc comment on toException explaining DEADLINE_EXCEEDED is included for
   completeness/future-proofing even though current call sites handle it first.
3. Extracted private helpers (createCancellationException, createRuntimeException,
   formatMessage, getDescriptionOrDefault) to eliminate duplication between
   toRuntimeException and toException.
4. Consistent message format: DEADLINE_EXCEEDED now uses the same "failed with a
   <code> gRPC status: <description>" prefix as all other status codes.

Agent-Logs-Url: https://github.com/microsoft/durabletask-java/sessions/747c79d2-a3fa-427c-8b3d-63515878b1d1

Co-authored-by: bachuv <15795068+bachuv@users.noreply.github.com>

Author: Copilot

client/src/main/java/com/microsoft/durabletask/StatusRuntimeExceptionHelper.java

@@ -25,21 +25,19 @@ static RuntimeException toRuntimeException(StatusRuntimeException e, String oper
         Status.Code code = e.getStatus().getCode();
         switch (code) {
             case CANCELLED:
-                CancellationException ce = new CancellationException(
-                        "The " + operationName + " operation was canceled.");
-                ce.initCause(e);
-                return ce;
+                return createCancellationException(e, operationName);
             default:
-                return new RuntimeException(
-                        "The " + operationName + " operation failed with a " + code + " gRPC status: "
-                                + e.getStatus().getDescription(),
-                        e);
+                return createRuntimeException(e, operationName, code);
         }
     }
 
     /**
      * Translates a {@link StatusRuntimeException} into an appropriate SDK-level checked exception
      * for operations that declare {@code throws TimeoutException}.
+     * <p>
+     * Note: The DEADLINE_EXCEEDED case is included for completeness and future-proofing, even
+     * though current call sites handle DEADLINE_EXCEEDED before falling through to this method.
+     * This ensures centralized translation if call sites are refactored in the future.
      *
      * @param e the gRPC exception to translate
      * @param operationName the name of the operation that failed, used in exception messages
@@ -50,20 +48,37 @@ static Exception toException(StatusRuntimeException e, String operationName) {
         switch (code) {
             case DEADLINE_EXCEEDED:
                 return new TimeoutException(
-                        "The " + operationName + " operation timed out: " + e.getStatus().getDescription());
+                        formatMessage(operationName, code, getDescriptionOrDefault(e)));
             case CANCELLED:
-                CancellationException ce = new CancellationException(
-                        "The " + operationName + " operation was canceled.");
-                ce.initCause(e);
-                return ce;
+                return createCancellationException(e, operationName);
             default:
-                return new RuntimeException(
-                        "The " + operationName + " operation failed with a " + code + " gRPC status: "
-                                + e.getStatus().getDescription(),
-                        e);
+                return createRuntimeException(e, operationName, code);
         }
     }
 
+    private static CancellationException createCancellationException(
+            StatusRuntimeException e, String operationName) {
+        CancellationException ce = new CancellationException(
+                "The " + operationName + " operation was canceled.");
+        ce.initCause(e);
+        return ce;
+    }
+
+    private static RuntimeException createRuntimeException(
+            StatusRuntimeException e, String operationName, Status.Code code) {
+        return new RuntimeException(
+                formatMessage(operationName, code, getDescriptionOrDefault(e)), e);
+    }
+
+    private static String formatMessage(String operationName, Status.Code code, String description) {
+        return "The " + operationName + " operation failed with a " + code + " gRPC status: " + description;
+    }
+
+    private static String getDescriptionOrDefault(StatusRuntimeException e) {
+        String description = e.getStatus().getDescription();
+        return description != null ? description : "(no description)";
+    }
+
     // Cannot be instantiated
     private StatusRuntimeExceptionHelper() {
     }

client/src/test/java/com/microsoft/durabletask/StatusRuntimeExceptionHelperTest.java

@@ -56,6 +56,7 @@ void toRuntimeException_unavailableStatus_returnsRuntimeException() {
         assertNotEquals(CancellationException.class, result.getClass());
         assertTrue(result.getMessage().contains("terminate"));
         assertTrue(result.getMessage().contains("UNAVAILABLE"));
+        assertTrue(result.getMessage().contains("Connection refused"));
         assertSame(grpcException, result.getCause());
     }
 
@@ -96,6 +97,19 @@ void toRuntimeException_preservesOperationName() {
         assertTrue(result.getMessage().contains("customOperationName"));
     }
 
+    @Test
+    void toRuntimeException_nullDescription_usesDefaultFallback() {
+        StatusRuntimeException grpcException = new StatusRuntimeException(Status.INTERNAL);
+
+        RuntimeException result = StatusRuntimeExceptionHelper.toRuntimeException(
+                grpcException, "testOp");
+
+        assertTrue(result.getMessage().contains("(no description)"),
+                "Expected '(no description)' fallback but got: " + result.getMessage());
+        assertFalse(result.getMessage().contains("null"),
+                "Message should not contain literal 'null': " + result.getMessage());
+    }
+
     // Tests for toException (checked exception variant)
 
     @Test
@@ -108,7 +122,20 @@ void toException_deadlineExceededStatus_returnsTimeoutException() {
 
         assertInstanceOf(TimeoutException.class, result);
         assertTrue(result.getMessage().contains("waitForInstanceStart"));
-        assertTrue(result.getMessage().contains("timed out"));
+        assertTrue(result.getMessage().contains("DEADLINE_EXCEEDED"));
+    }
+
+    @Test
+    void toException_deadlineExceededStatus_usesConsistentMessageFormat() {
+        StatusRuntimeException grpcException = new StatusRuntimeException(
+                Status.DEADLINE_EXCEEDED.withDescription("timeout after 5s"));
+
+        Exception result = StatusRuntimeExceptionHelper.toException(
+                grpcException, "purgeInstances");
+
+        assertInstanceOf(TimeoutException.class, result);
+        assertTrue(result.getMessage().contains("failed with a DEADLINE_EXCEEDED gRPC status"),
+                "Expected consistent message format but got: " + result.getMessage());
     }
 
     @Test
@@ -148,4 +175,18 @@ void toException_internalStatus_returnsRuntimeExceptionWithCause() {
         assertInstanceOf(RuntimeException.class, result);
         assertSame(grpcException, result.getCause());
     }
+
+    @Test
+    void toException_nullDescription_usesDefaultFallback() {
+        StatusRuntimeException grpcException = new StatusRuntimeException(Status.DEADLINE_EXCEEDED);
+
+        Exception result = StatusRuntimeExceptionHelper.toException(
+                grpcException, "testOp");
+
+        assertInstanceOf(TimeoutException.class, result);
+        assertTrue(result.getMessage().contains("(no description)"),
+                "Expected '(no description)' fallback but got: " + result.getMessage());
+        assertFalse(result.getMessage().contains("null"),
+                "Message should not contain literal 'null': " + result.getMessage());
+    }
 }