First-chance exceptions when writing UsedReferences.log

[KirillOsenkov]

When the analyzer runs (pretty much on every keystroke) it fails with this exception because the file is locked:

System.IO.IOException: The process cannot access the file 'C:\temp\wpf\obj\Debug\net472\_ReferenceTrimmer_UsedReferences.log' because it is being used by another process.
   at void System.IO.__Error.WinIOError(int errorCode, string maybeFullPath)
   at void System.IO.FileStream.Init(string path, FileMode mode, FileAccess access, int rights, bool useRights, FileShare share, int bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, string msgPath, bool bFromProxy, bool useLongPath, bool checkHost)
   at new System.IO.FileStream(string path, FileMode mode, FileAccess access, FileShare share, int bufferSize, FileOptions options, string msgPath, bool bFromProxy, bool useLongPath, bool checkHost)
   at Stream System.IO.StreamWriter.CreateFile(string path, bool append, bool checkHost)
   at new System.IO.StreamWriter(string path, bool append, Encoding encoding, int bufferSize, bool checkHost) x 2
   at void System.IO.File.WriteAllLines(string path, IEnumerable<string> contents)
   at void ReferenceTrimmer.Analyzer.ReferenceTrimmerAnalyzer.DumpUsedReferences(CompilationAnalysisContext context) in D:/a/ReferenceTrimmer/ReferenceTrimmer/src/Analyzer/ReferenceTrimmerAnalyzer.cs:line 85
   at void Microsoft.CodeAnalysis.Diagnostics.AnalyzerExecutor.ExecuteCompilationActions(ImmutableArray<CompilationAnalyzerAction> compilationActions, DiagnosticAnalyzer analyzer, CompilationEvent compilationEvent, CancellationToken cancellationToken)+((Action<CompilationAnalysisContext> action, CompilationAnalysisContext context) data) => { } in C:/Roslyn/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerExecutor.cs:line 332
   at void Microsoft.CodeAnalysis.Diagnostics.AnalyzerExecutor.ExecuteAndCatchIfThrows_NoLock<TArg>(DiagnosticAnalyzer analyzer, Action<TArg> analyze, TArg argument, AnalysisContextInfo? info, CancellationToken cancellationToken) in C:/Roslyn/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerExecutor.cs:line 1177
   at void Microsoft.CodeAnalysis.Diagnostics.AnalyzerExecutor.ExecuteAndCatchIfThrows<TArg>(DiagnosticAnalyzer analyzer, Action<TArg> analyze, TArg argument, AnalysisContextInfo? contextInfo, CancellationToken cancellationToken) in C:/Roslyn/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerExecutor.cs:line 1161
   at void Microsoft.CodeAnalysis.Diagnostics.AnalyzerExecutor.ExecuteCompilationActions(ImmutableArray<CompilationAnalyzerAction> compilationActions, DiagnosticAnalyzer analyzer, CompilationEvent compilationEvent, CancellationToken cancellationToken) in C:/Roslyn/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerExecutor.cs:line 322
   at void Microsoft.CodeAnalysis.Diagnostics.AnalyzerDriver.ExecuteCompilationActions(ImmutableArray<ValueTuple<DiagnosticAnalyzer, ImmutableArray<CompilationAnalyzerAction>>> compilationActionsMap, CompilationEvent compilationEvent, AnalysisScope analysisScope, CancellationToken cancellationToken) in C:/Roslyn/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerDriver.cs:line 1939
   at async ValueTask<EventProcessedState> Microsoft.CodeAnalysis.Diagnostics.AnalyzerDriver.TryProcessEventCoreAsync(CompilationEvent compilationEvent, AnalysisScope analysisScope, CancellationToken cancellationToken) in C:/Roslyn/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerDriver.cs:line 1730
   at void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<TResult>.Start<TStateMachine>(ref TStateMachine stateMachine)
   at ValueTask<EventProcessedState> Microsoft.CodeAnalysis.Diagnostics.AnalyzerDriver.TryProcessEventCoreAsync(CompilationEvent compilationEvent, AnalysisScope analysisScope, CancellationToken cancellationToken)
   at async Task Microsoft.CodeAnalysis.Diagnostics.AnalyzerDriver.ProcessEventAsync(CompilationEvent e, AnalysisScope analysisScope, CancellationToken cancellationToken) in C:/Roslyn/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerDriver.cs:line 1629
   at void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.Start<TStateMachine>(ref TStateMachine stateMachine)
   at Task Microsoft.CodeAnalysis.Diagnostics.AnalyzerDriver.ProcessEventAsync(CompilationEvent e, AnalysisScope analysisScope, CancellationToken cancellationToken)
   at async Task<CompilationCompletedEvent> Microsoft.CodeAnalysis.Diagnostics.AnalyzerDriver.ProcessCompilationEventsCoreAsync(AnalysisScope analysisScope, bool prePopulatedEventQueue, CancellationToken cancellationToken) in C:/Roslyn/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerDriver.cs:line 1612
   at void System.Runtime.CompilerServices.AsyncTaskMethodBuilder<TResult>.Start<TStateMachine>(ref TStateMachine stateMachine)
   at Task<CompilationCompletedEvent> Microsoft.CodeAnalysis.Diagnostics.AnalyzerDriver.ProcessCompilationEventsCoreAsync(AnalysisScope analysisScope, bool prePopulatedEventQueue, CancellationToken cancellationToken)
   at async Task Microsoft.CodeAnalysis.Diagnostics.AnalyzerDriver.ProcessCompilationEventsAsync(AnalysisScope analysisScope, bool prePopulatedEventQueue, CancellationToken cancellationToken) in C:/Roslyn/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerDriver.cs:line 1547
   at void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.Start<TStateMachine>(ref TStateMachine stateMachine)
   at Task Microsoft.CodeAnalysis.Diagnostics.AnalyzerDriver.ProcessCompilationEventsAsync(AnalysisScope analysisScope, bool prePopulatedEventQueue, CancellationToken cancellationToken)
   at async Task Microsoft.CodeAnalysis.Diagnostics.AnalyzerDriver.ExecutePrimaryAnalysisTaskAsync(AnalysisScope analysisScope, bool usingPrePopulatedEventQueue, CancellationToken cancellationToken) in C:/Roslyn/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerDriver.cs:line 697
   at void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.Start<TStateMachine>(ref TStateMachine stateMachine)
   at Task Microsoft.CodeAnalysis.Diagnostics.AnalyzerDriver.ExecutePrimaryAnalysisTaskAsync(AnalysisScope analysisScope, bool usingPrePopulatedEventQueue, CancellationToken cancellationToken)
   at async Task Microsoft.CodeAnalysis.Diagnostics.AnalyzerDriver.AttachQueueAndProcessAllEventsAsync(AsyncQueue<CompilationEvent> eventQueue, AnalysisScope analysisScope, CancellationToken cancellationToken) in C:/Roslyn/src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerDriver.cs:line 641
   at void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.Start<TStateMachine>(ref TStateMachine stateMachine)
   at Task Microsoft.CodeAnalysis.Diagnostics.AnalyzerDriver.AttachQueueAndProcessAllEventsAsync(AsyncQueue<CompilationEvent> eventQueue, AnalysisScope analysisScope, CancellationToken cancellationToken)
   at async Task Microsoft.CodeAnalysis.Diagnostics.CompilationWithAnalyzers.ComputeAnalyzerDiagnosticsAsync(AnalysisScope analysisScope, CancellationToken cancellationToken)+attachQueueAndProcessAllEventsAsync(?)
   at void System.Runtime.CompilerServices.AsyncTaskMethodBuilder.Start<TStateMachine>(ref TStateMachine stateMachine)
   at Task Microsoft.CodeAnalysis.Diagnostics.CompilationWithAnalyzers.ComputeAnalyzerDiagnosticsAsync(AnalysisScope analysisScope, CancellationToken cancellationToken)+attachQueueAndProcessAllEventsAsync(ArrayBuilder<ValueTuple<AnalysisScope, ImmutableArray<CompilationEvent>>> builder, AnalyzerDriver driver, CancellationToken cancellationToken)
   at async Task Microsoft.CodeAnalysis.Diagnostics.CompilationWithAnalyzers.ComputeAnalyzerDiagnosticsAsync(AnalysisScope analysisScope, CancellationToken cancellationToken)

[KirillOsenkov]

If I understand correctly this is writing to the file which was passed as an additional file to the analyzer.

Unfortunately this is problematic as it can lead to problems with analyzers rerunning when the file has changed. Roslyn workspace monitors all files that are input to the compilation for changes on disk, and when they change it retriggers analyzers to feed them the latest inputs. When you write to an input file Roslyn workspace may see this change and if it happens outside the throttling window it will retrigger the analyzer.

In general I understand why this is designed as an analyzer (to tap into the Roslyn world to get the accurate info about references), however it's perhaps undesirable that this runs pretty much on every keystroke in the IDE. Is this an incremental analyzer?

[dfederm]

Interesting. This issue was likely introduced in #81.

This is not really intended to be an incremental analyzer. I would not mind if we only ran it on "real" builds. Do you know if there is an easy way to detect this?

[KirillOsenkov]

yes, it feels like this should be a command-line/batch tool, not an interactive tool. Perhaps we can have it disabled by default and only add the analyzer if a property is set? and have people only set that in CI?

[KirillOsenkov]

as a short term workaround we can add a Mutex or a lock around File.WriteAllText and have the whole thing in a try/catch

[dfederm]

Fixed by #90