opentelemetry-js: Unable to rely on AsyncHooksScopeManager when wrapping async functions

Please answer these questions before submitting a bug report.

What version of OpenTelemetry are you using?

0.3.3

What version of Node are you using?

13.6.0

What did you do?

I’m using the AsyncHooksScopeManager to keep track of my current scope. I’m expecting to be able to call tracer.withSpan(...) and from within call tracer.getCurrentSpan() and have it provide me with the span I am executing inside of. I’ve provided a failing unit test

import { AsyncHooksScopeManager } from '@opentelemetry/scope-async-hooks'
import { InMemorySpanExporter } from '@opentelemetry/tracing'
import {
  BasicTracerRegistry,
  SimpleSpanProcessor,
} from '@opentelemetry/tracing'

function makeTracer(exporter: InMemorySpanExporter) {
  const config = {
    scopeManager: new AsyncHooksScopeManager(),
  }
  const registry = new BasicTracerRegistry()
  registry.addSpanProcessor(new SimpleSpanProcessor(exporter))
  const tracer = registry.getTracer('tracer', undefined, config)
  return tracer
}

describe('async handling should fail', () => {
  const exporter = new InMemorySpanExporter()

  async function demo(ms): Promise<string> {
    const tracer = makeTracer(exporter)

    const span = tracer.startSpan('my span')

    return tracer.withSpan(span, async () => {
      await new Promise(resolve => setTimeout(resolve, ms))
      tracer.getCurrentSpan().addEvent('root-event', {})

      return 'ok'
    })
  }

  it('will not be able to retrieve the current span from within the `withSpan` block', async () => {
    const result = await demo(0)
    expect(result).toBe('ok')
    expect(exporter.getFinishedSpans().length).toBe(1)
    expect(exporter.getFinishedSpans()[0].events.length).toBe(1)
  })
})

What did you see instead?

Instead of giving me the current span, the ScopeManager has continued executing (because it doesn’t await) and has deleted the scope for that span. So calling getCurrentSpan() is returning undefined