Feature: support next_retry_delay when raising ApplicationError from …

…an activity

temporalio/converter.py

@@ -34,6 +34,7 @@
     overload,
 )
 
+import google.protobuf.duration_pb2
 import google.protobuf.json_format
 import google.protobuf.message
 import google.protobuf.symbol_database
@@ -843,6 +844,10 @@ def _error_to_failure(
                 failure.application_failure_info.details.CopyFrom(
                     payload_converter.to_payloads_wrapper(error.details)
                 )
+            if error.next_retry_delay:
+                delay = google.protobuf.duration_pb2.Duration()
+                delay.FromTimedelta(error.next_retry_delay)
+                failure.application_failure_info.next_retry_delay.CopyFrom(delay)
         elif isinstance(error, temporalio.exceptions.TimeoutError):
             failure.timeout_failure_info.SetInParent()
             failure.timeout_failure_info.timeout_type = (

temporalio/exceptions.py

@@ -1,6 +1,7 @@
 """Common Temporal exceptions."""
 
 import asyncio
+from datetime import timedelta
 from enum import IntEnum
 from typing import Any, Optional, Sequence, Tuple
 
@@ -78,6 +79,7 @@ def __init__(
         *details: Any,
         type: Optional[str] = None,
         non_retryable: bool = False,
+        next_retry_delay: Optional[timedelta] = None,
     ) -> None:
         """Initialize an application error."""
         super().__init__(
@@ -88,6 +90,7 @@ def __init__(
         self._details = details
         self._type = type
         self._non_retryable = non_retryable
+        self._next_retry_delay = next_retry_delay
 
     @property
     def details(self) -> Sequence[Any]:
@@ -109,6 +112,16 @@ def non_retryable(self) -> bool:
         """
         return self._non_retryable
 
+    @property
+    def next_retry_delay(self) -> Optional[timedelta]:
+        """Delay before the next activity retry attempt.
+
+        User activity code may set this when raising ApplicationError to specify
+        a delay before the next activity retry. Ignored if set when raising
+        ApplicationError from workflow code.
+        """
+        return self._next_retry_delay
+
 
 class CancelledError(FailureError):
     """Error raised on workflow/activity cancellation."""