Fix: No more spurious restart needed in the IDE

[MikaelMayer]

Fixes #4833

Description

I replaced the openFileCount by openFiles so that closing a document, even if unexpected like VSCode does randomly, won't trigger the Compilation object to be disposed, which crashes the IDE every 3-4 minutes on projects with multiple files open.

How has this been tested?

I have been enjoying the IDE for 20 minutes straight without restarting it. It's a fantastic experience. I'm going to turn on "verification on change" again.

By submitting this pull request, I confirm that my contribution is made under the terms of the MIT license.

[atomb]

What role does the 1 serve here? Could this be a set instead of a map?

[MikaelMayer]

The only concurrent set I found in C# is a ConcurrentBag but it curiously does not have a method for removing a specific element.

[keyboardDrummer]

Amazing, thanks :)

@MikaelMayer I'm a little concerned that we didn't get to understand how you got the stack trace:

System.ObjectDisposedException: Cannot access a disposed object.
Object name: 'EventLoopScheduler'.
   at System.Reactive.Concurrency.EventLoopScheduler.Schedule[TState](TState state, TimeSpan dueTime, Func`3 action) in /_/Rx.NET/Source/src/System.Reactive/Concurrency/EventLoopScheduler.cs:line 173
   at System.Reactive.ObserveOnObserverNew`1.Schedule() in /_/Rx.NET/Source/src/System.Reactive/Internal/ScheduledObserver.cs:line 486
   at System.Reactive.Subjects.Subject`1.OnNext(T value) in /_/Rx.NET/Source/src/System.Reactive/Subjects/Subject.cs:line 139
   at System.Reactive.Subjects.Subject`1.OnNext(T value) in /_/Rx.NET/Source/src/System.Reactive/Subjects/Subject.cs:line 139
   at Microsoft.Dafny.LanguageServer.Language.ObservableErrorReporter.AddDiagnosticForFile(DafnyDiagnostic dafnyDiagnostic, MessageSource messageSource, Uri uri) in C:\Users\mimayere\Documents\dafny\Source\DafnyLanguageServer\Language\ObservableErrorReporter.cs:line 139

But then again I wouldn't think the exception from this stack trace causes an issue, because it relates to already closed project managers, so we can leave it for now

[MikaelMayer]

Amazing, thanks :)

@MikaelMayer I'm a little concerned that we didn't get to understand how you got the stack trace:

System.ObjectDisposedException: Cannot access a disposed object.
Object name: 'EventLoopScheduler'.
   at System.Reactive.Concurrency.EventLoopScheduler.Schedule[TState](TState state, TimeSpan dueTime, Func`3 action) in /_/Rx.NET/Source/src/System.Reactive/Concurrency/EventLoopScheduler.cs:line 173
   at System.Reactive.ObserveOnObserverNew`1.Schedule() in /_/Rx.NET/Source/src/System.Reactive/Internal/ScheduledObserver.cs:line 486
   at System.Reactive.Subjects.Subject`1.OnNext(T value) in /_/Rx.NET/Source/src/System.Reactive/Subjects/Subject.cs:line 139
   at System.Reactive.Subjects.Subject`1.OnNext(T value) in /_/Rx.NET/Source/src/System.Reactive/Subjects/Subject.cs:line 139
   at Microsoft.Dafny.LanguageServer.Language.ObservableErrorReporter.AddDiagnosticForFile(DafnyDiagnostic dafnyDiagnostic, MessageSource messageSource, Uri uri) in C:\Users\mimayere\Documents\dafny\Source\DafnyLanguageServer\Language\ObservableErrorReporter.cs:line 139

But then again I wouldn't think the exception from this stack trace causes an issue, because it relates to already closed project managers, so we can leave it for now

I got this exception while putting breakpoints on disposed method, which apparently was caught here:

• DafnyTextDocumentHandler.cs line 102, telemetryPublisher.PublishUnhandledException(e);
  This project was closed but should not as I still had files open.