Fix legacy entity protocol: propagate call_entity failures and stop double-encoding results

[andystaples]

Two related fixes to OrchestrationContext.call_entity under the legacy entity protocol — the protocol the Azure Functions Durable (WebJobs) extension uses when talking to out-of-proc Python workers. The current entity protocol (entityOperationCompleted / entityOperationFailed, used by durabletask.azuremanaged / DTS) already behaved correctly; only the legacy eventRaised-based path was affected.

1. Entity operation failures were not propagated

A failed entity operation was silently completing (typically returning None) instead of raising, so orchestrations could never observe or handle the failure.

Legacy-protocol entity results arrive as an eventRaised handled by _handle_entity_event_raised, which unconditionally called entity_task.complete(...) and never inspected the response for a failure indicator. The wire contract is DurableTask.Core's ResponseMessage, where IsErrorResult => exceptionType != null || failureDetails != null (exceptionType carries the error message; failureDetails carries a structured FailureDetails).

Fix: _handle_entity_event_raised now detects a failed response and fails the task with an EntityOperationFailedException, so an awaiting call_entity raises TaskFailedError — matching the current entity protocol and the .NET SDK (CallEntityAsync throws EntityOperationFailedException when the result IsError).

2. Successful results were double-encoded

The ResponseMessage.result field holds a serialized JSON string of the return value (just like the new protocol's entityOperationCompleted.output). The success path used coerce, which applies a type to an already-parsed value and does not parse JSON strings. As a result, string/dict/list returns arrived double-encoded (e.g. a returned "done" surfaced as "\"done\""), and only numeric returns with an explicit return_type happened to work.

Fix: deserialize the result string (type-directed) instead of coercing it, mirroring the current-protocol handler.

Also addressed

• Cleaned up the legacy eventRaised dispatch to pop() _entity_task_id_map / _entity_lock_task_id_map entries once handled (they were looked up with get() and never removed), preventing unbounded map growth in long-running orchestrations — consistent with the new-protocol handlers. (From PR review.)

Changes

• durabletask/worker.py: failure detection + propagation in _handle_entity_event_raised; type-directed deserialization of the result; pop() map cleanup.
• durabletask/internal/helpers.py: entity_response_failure_details(...) plus a recursive FailureDetails converter.
• tests/durabletask/test_orchestration_executor.py: legacy-protocol tests for failure via failureDetails, failure via exceptionType, and a parametrized success round-trip across str / int / float / bool / dict / list (no return_type required).
• CHANGELOG.md: FIXED entries for both bugs.

Validation

• New legacy-protocol tests pass; entity + orchestration-executor suites pass.
• flake8 and Pylance clean on changed files.
• durabletask.azuremanaged uses the current protocol and is unaffected.

[Copilot]

Pull request overview

This PR fixes a correctness gap in the core durabletask SDK where entity operation failures were not propagated to orchestrations when using the legacy entity protocol (used by the Azure Functions Durable/WebJobs extension). It aligns legacy-protocol behavior with the current protocol (and .NET) by detecting failure indicators in legacy ResponseMessage payloads and failing the awaiting call_entity task accordingly.

Changes:

• Added legacy ResponseMessage failure detection/conversion helpers to produce TaskFailureDetails when failureDetails or exceptionType indicate an entity operation failure.
• Updated legacy-protocol eventRaised handling to fail call_entity tasks with EntityOperationFailedException when failures are detected.
• Added orchestration executor tests covering legacy-protocol entity call failure/success cases, and documented the fix in CHANGELOG.md.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
tests/durabletask/test_orchestration_executor.py	Adds regression tests for legacy-protocol entity call failure propagation (both failureDetails and exceptionType) and a success round-trip.
durabletask/worker.py	Detects legacy-protocol entity call failures in eventRaised handling and propagates them as task failures to orchestrations.
durabletask/internal/helpers.py	Adds helpers to extract/convert legacy ResponseMessage failure data into TaskFailureDetails.
CHANGELOG.md	Documents the user-visible fix under ## Unreleased → FIXED.