[copilot-finds] Bug: getMethodNameForAction() missing SENDEVENT, SENDENTITYMESSAGE, and TERMINATEORCHESTRATION cases, crashing non-determinism error handler

[github-actions]

Problem

getMethodNameForAction() in packages/durabletask-js/src/worker/index.ts (line 36-55) only handles 4 of the 7 valid OrchestratorAction types: SCHEDULETASK, CREATETIMER, CREATESUBORCHESTRATION, and COMPLETEORCHESTRATION.

The three missing cases are:

• SENDEVENT (produced by context.sendEvent())
• SENDENTITYMESSAGE (produced by context.callEntity(), context.signalEntity(), context.lockEntities())
• TERMINATEORCHESTRATION

Root Cause

When orchestration code is changed between runs (a non-determinism scenario), the orchestration executor calls getWrongActionTypeError() which in turn calls getMethodNameForAction() to produce a descriptive NonDeterminismError message. If the mismatched action is a SENDEVENT, SENDENTITYMESSAGE, or TERMINATEORCHESTRATION type, getMethodNameForAction() falls through to the default case and throws a generic Error("Unknown action type: N") instead of returning the method name.

This means the user sees an unhelpful "Unknown action type: 5" crash instead of the intended diagnostic message like "A previous execution called callActivity with ID=1, but the current execution is instead trying to call sendEvent...".

Scenario

1. Version 1 of an orchestrator calls context.callActivity("myActivity") at sequence ID 1
2. An instance starts running and completes the activity
3. Code is updated: version 2 calls context.sendEvent("instance", "event") at sequence ID 1
4. On replay, history has TaskScheduled at ID=1, but _pendingActions[1] is now a SENDEVENT action
5. handleTaskScheduled() detects the mismatch and calls getWrongActionTypeError(1, "callActivity", sendEventAction)
6. getMethodNameForAction(sendEventAction) throws Error("Unknown action type: 5") instead of returning "sendEvent"

The same pattern applies to entity orchestrations that use callEntity/signalEntity/lockEntities.

Proposed Fix

Add the three missing cases to the switch statement in getMethodNameForAction().

Impact

Severity: Medium — Affects error diagnostics for non-determinism in orchestrations using entities or sendEvent. Users get an unhelpful crash error instead of the proper NonDeterminismError that explains the history mismatch.