[Bug]: Package Manager Console initialization might cause deadlocks

[zivkan]

NuGet Product Used

Visual Studio Package Manager Console

Product Version

all?

Worked before?

No response

Impact

It's more difficult to complete my work

Repro Steps & Context

There's a timing bug, which means that it can't be reproduced on demand, it just depends if everything lines up in the wrong way.

Huge thanks to @sharwell and @CyrusNajmabadi for finding and telling us about the problem (and how to fix

Low level details are:

During PMC initialization, RunspaceManager.CreateRunspace casts a DTE object to DTE2, but at this time it's running on a background thread. Since DTE(2) is a COM object, it needs the UI thread to do the cast.

However, if something is blocking the UI thread, NuGet/PMC can't get the UI thread to do the cast. If the code blocking the UI thread called a NuGet API and is waiting for the result, this causes a deadlock.

A few lines earlier in RunspaceManager.cs, PMC gets the DTE object via NuGet's ServiceLocator, which correctly uses JTF to switch to the UI thread. Hence, by getting the service locator to cast to DTE2, rather than doing it from a background thread, this should eliminate the risk of deadlock.

Verbose Logs

No response