Warn on unfinished handlers and provide workflow.allHandlersFinished() API

[dandavison]

Fixes #1434 and #1435.

• new workflow API to wait for all signal and update handlers to be finished:
  await workflow.condition(() => workflow.allHandlersFinished())
• By default, warn when workflow exits with unfinished handlers, but not when a handler finishes due to workflow cancellation or workflow failure.
• Warnings controlled by HandlerUnfinishedPolicy

[bergundy]

I'm concerned with allHandlersFinished returning true between handling of a signal and an update.

I noticed that updates aren't reordered an put in the first activation batch:

sdk-typescript/packages/worker/src/workflow/vm-shared.ts

Line 315 in 9d31dbd

const [signals, nonSignals] = partition(nonPatches, ({ signalWorkflow }) => signalWorkflow != null);

This means that this workflow won't get a chance to see an update:

import * as workflow from '@temporalio/workflow';

const fooSignal = workflow.defineSignal('foo');
const fooUpdate = workflow.defineUpdate('foo');

export async function http(): Promise<string> {
  var numFoos = 0;

  workflow.setHandler(fooSignal, () => {
    numFoos++
  });

  workflow.setHandler(fooUpdate, () => {
    numFoos++
  });

  await workflow.condition(workflow.allHandlersFinished);
  return `foos: ${numFoos}`;
}

Starter:

  const handle = await client.workflow.start(workflowType, {
    workflowId,
    taskQueue: 'test',
    args,
  });
  await handle.signal('foo');
  await handle.startUpdate('foo', {
    waitForStage: WorkflowUpdateStage.ACCEPTED,
  });

Fixing this would require to break history compatibility or find a safe way to patch outside of the sandbox, which we haven't done before.

[dandavison]

I'm concerned with allHandlersFinished returning true between handling of a signal and an update.

@bergundy and I discussed this. There is indeed a bug, though not introduced in this PR and therefore not blocking this PR. We've opened #1474

[Sushisource]

Should also close #1435

[mjameswh]

Still a few nits, but I'm ok to fix those in a follow-up PR.

[dandavison]

Thanks very much for reviewing @mjameswh!

Still a few nits, but I'm ok to fix those in a follow-up PR.

The only thing I've pushed to a follow-up is the task of generating example stack traces to review our use of untrackPromise: #1486, which was needed even before this PR.