Variable Expansion: ScriptProperty ToStrings are slow to perform

[JustinGrote]

Per @SeeminglyScience it's probably because the ToString is trying to marshal to the pipeline thread and deadlocking.

[JustinGrote]

@SeeminglyScience looks like it's not hard-hanging, just a performance issue. Could this have to do with the marshaling still?

Capture.mp4

[JustinGrote]

Narrowed it down to this loop for enumerables that is "slow", I'll dig deeper into VariableDetails later.

PowerShellEditorServices/src/PowerShellEditorServices/Services/DebugAdapter/Debugging/VariableDetails.cs

Lines 338 to 344 in 624fe30

	foreach (var item in enumerable)
	{
	childVariables.Add(
	new VariableDetails(
	"[" + i++ + "]",
	item));
	}

[SeeminglyScience]

@SeeminglyScience looks like it's not hard-hanging, just a performance issue. Could this have to do with the marshaling still?

Yep!

In certain circumstances (like this one) it will timeout after 250ms and then just invoke it anyway from a different thread (while still targeting the same runspace) potentially causing state corruption. So I'd say that still perfectly explains it and potentially makes it a little bit more scary.

[JustinGrote]

Here's the culprit:

PowerShellEditorServices/src/PowerShellEditorServices/Services/DebugAdapter/Debugging/VariableDetails.cs

Line 198 in 624fe30

string valueToString = value.SafeToString();

If you set it to null instead of SafeToString(), everything is fast again.

[JustinGrote]

More specifically:

PowerShellEditorServices/src/PowerShellEditorServices/Utility/Extensions.cs

Line 25 in 3274c23

str = obj.ToString();

@SeeminglyScience how would I get this obj.ToString() method on the correct invocation? It does feel like about a 250ms delay on each invocation.

[JustinGrote]

Adding @SeeminglyScience as I've hit my limits on figuring this out for now :)

[andyleejordan]

And fixed, with your test too!