Activities not started with tags

[TheAngryByrd]

Please provide a succinct description of the issue.

👋 I'm trying to use the tracing information inside FSC for FSAC to provide feedback when something is being typechecked. I'm using an ActivityListener like so:

  let mutable inflightEvents = ConcurrentDictionary<_, ServerProgressReport>()

  let shouldListenTo (act : ActivitySource) =
    act.Name = "fsc"

  let activityStarted (act : Activity) =
    let progressReport = new ServerProgressReport(lspClient)
    if inflightEvents.TryAdd(act.Id, progressReport) then

      progressReport.Begin($"Dependent Typecheck {act.DisplayName}")
      |> Async.StartImmediate
    ()

  let activityStopped (act : Activity) =
    match inflightEvents.TryRemove(act.Id) with
    | true, v -> v.End() |> Async.StartImmediate
    | _ -> ()

  let listener = new ActivityListener(
    ShouldListenTo = shouldListenTo,
    Sample = (fun _ ->  ActivitySamplingResult.AllData),
    ActivityStarted  = activityStarted,
    ActivityStopped = activityStopped
  )
  do ActivitySource.AddActivityListener listener

The activityStarted does get messages for the name like BackgroundCompiler.CreateOneIncrementalBuilder. However, this request is missing the associated tags. Which means we can't tell the user which file is being type checked currently.

This is because the Activity is started and created before tags are added:

fsharp/src/Compiler/Utilities/Activity.fs

Lines 65 to 74 in cd2babe

	let start (name: string) (tags: (string * string) seq) : IDisposable =
	let activity = activitySource.StartActivity(name)
	match activity with
	| null -> ()
	| activity ->
	for key, value in tags do
	activity.AddTag(key, value) |> ignore
	activity

I think the change would be rather straightforward:

    let start (name: string) (tags: (string * string) seq) : IDisposable =
        let activity = activitySource.CreateActivity(name, ActivityKind.Internal)

        match activity with
        | null -> ()
        | activity ->
            for key, value in tags do
                activity.AddTag(key, value) |> ignore

        activity.Start()

or possibly

    let start (name: string) (tags: (string * string) seq) : IDisposable =
        let tags = tags |> Seq.map (fun (k,v) -> KeyValuePair(k, box v))
        let activity = activitySource.StartActivity(ActivityKind.Internal, name = name, tags = tags)

        activity

[T-Gro]

Understood, I will make the construction atomic (from the event consumption point of view).
Will also expose the source name.