* Enable nullable
* Add a fast return to ReportFileSystemChanged when path should be ignored
* Use Span overloads of Path.* functions where possible
* IFileSystem: remove NormalizePath as Path.TrimEndingDirectorySeparator already checks if it's a root path
Did a simple search/replace on the whole repo (except the RSSDP project)
This reduces LOC and should improve performance (methods containing a throw statement don't get inlined)
```
if \((\w+) == null\)
\s+\{
\s+throw new ArgumentNullException\((.*)\);
\s+\}
```
```
ArgumentNullException.ThrowIfNull($1);
```
* Use Guid.Equals(Guid) instead of the == override
* Ban the usage of Guid.Equals(Object) to prevent accidental boxing
* Compare to default(Guid) instead of Guid.Empty
```
Error Message:
System.ArgumentNullException : Value cannot be null. (Parameter 'source')
Stack Trace:
at System.Linq.ThrowHelper.ThrowArgumentNullException(ExceptionArgument argument)
at System.Linq.Enumerable.Select[TSource,TResult](IEnumerable`1 source, Func`2 selector)
at Emby.Server.Implementations.Library.LibraryManager.ResolveItem(ItemResolveArgs args, IItemResolver[] resolvers) in /home/vsts/work/1/s/Emby.Server.Implementations/Library/LibraryManager.cs:line 475
at Emby.Server.Implementations.Library.LibraryManager.ResolvePath(FileSystemMetadata fileInfo, IDirectoryService directoryService, IItemResolver[] resolvers, Folder parent, String collectionType, LibraryOptions libraryOptions) in /home/vsts/work/1/s/Emby.Server.Implementations/Library/LibraryManager.cs:line 618
at Emby.Server.Implementations.Library.LibraryManager.ResolvePath(FileSystemMetadata fileInfo, Folder parent) in /home/vsts/work/1/s/Emby.Server.Implementations/Library/LibraryManager.cs:line 536
at Emby.Server.Implementations.Library.LibraryManager.GetUserRootFolder() in /home/vsts/work/1/s/Emby.Server.Implementations/Library/LibraryManager.cs:line 812
at Emby.Server.Implementations.Library.LibraryManager.GetCollectionFolders(BaseItem item) in /home/vsts/work/1/s/Emby.Server.Implementations/Library/LibraryManager.cs:line 2080
at Emby.Server.Implementations.Library.LibraryManager.GetLibraryOptions(BaseItem item) in /home/vsts/work/1/s/Emby.Server.Implementations/Library/LibraryManager.cs:line 2116
at MediaBrowser.Providers.Manager.ProviderManager.SaveMetadata(BaseItem item, ItemUpdateType updateType, IEnumerable`1 savers) in /home/vsts/work/1/s/MediaBrowser.Providers/Manager/ProviderManager.cs:line 672
at MediaBrowser.Providers.Manager.ProviderManager.SaveMetadata(BaseItem item, ItemUpdateType updateType) in /home/vsts/work/1/s/MediaBrowser.Providers/Manager/ProviderManager.cs:line 655
at Emby.Server.Implementations.Library.LibraryManager.RunMetadataSavers(BaseItem item, ItemUpdateType updateReason) in /home/vsts/work/1/s/Emby.Server.Implementations/Library/LibraryManager.cs:line 2017
at Emby.Server.Implementations.Library.LibraryManager.UpdateItemsAsync(IReadOnlyList`1 items, BaseItem parent, ItemUpdateType updateReason, CancellationToken cancellationToken) in /home/vsts/work/1/s/Emby.Server.Implementations/Library/LibraryManager.cs:line 1975
at Emby.Server.Implementations.Library.LibraryManager.CreateRootFolder() in /home/vsts/work/1/s/Emby.Server.Implementations/Library/LibraryManager.cs:line 775
at Emby.Server.Implementations.Library.LibraryManager.get_RootFolder() in /home/vsts/work/1/s/Emby.Server.Implementations/Library/LibraryManager.cs:line 180
at Emby.Server.Implementations.IO.LibraryMonitor.Start() in /home/vsts/work/1/s/Emby.Server.Implementations/IO/LibraryMonitor.cs:line 135
at Emby.Server.Implementations.IO.LibraryMonitorStartup.RunAsync() in /home/vsts/work/1/s/Emby.Server.Implementations/IO/LibraryMonitorStartup.cs:line 26
at Emby.Server.Implementations.ApplicationHost.StartEntryPoints(IEnumerable`1 entryPoints, Boolean isBeforeStartup)+MoveNext() in /home/vsts/work/1/s/Emby.Server.Implementations/ApplicationHost.cs:line 518
at System.Threading.Tasks.Task.WhenAll(IEnumerable`1 tasks)
at Emby.Server.Implementations.ApplicationHost.RunStartupTasksAsync(CancellationToken cancellationToken) in /home/vsts/work/1/s/Emby.Server.Implementations/ApplicationHost.cs:line 502
at Jellyfin.Server.Integration.Tests.JellyfinApplicationFactory.CreateServer(IWebHostBuilder builder) in /home/vsts/work/1/s/tests/Jellyfin.Server.Integration.Tests/JellyfinApplicationFactory.cs:line 101
at Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory`1.EnsureServer()
at Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory`1.CreateDefaultClient(DelegatingHandler[] handlers)
at Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory`1.CreateDefaultClient(Uri baseAddress, DelegatingHandler[] handlers)
at Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory`1.CreateClient(WebApplicationFactoryClientOptions options)
at Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory`1.CreateClient()
at Jellyfin.Server.Integration.Tests.Controllers.ActivityLogControllerTests.ActivityLog_GetEntries_Ok() in /home/vsts/work/1/s/tests/Jellyfin.Server.Integration.Tests/Controllers/ActivityLogControllerTests.cs:line 21
--- End of stack trace from previous location ---
```
