Latest dotnet (v9.0.301) breaks omnisharp

[akarel-mb]

After updating to latest dotnet (v9.0.301 from v9.0.203), I am getting an exception on init: System.MissingMethodException: Method not found: 'System.ReadOnlySpan'1<Char> Microsoft.IO.Path.GetFileName(System.ReadOnlySpan'1<Char>)' for every project it attempts to load. Prior to the update omnisharp lsp was working as expected.

os: Windows 11
dotnet versoin: 9.0.301

Full stack trace:

Failed to load project file 'some-project-file.csproj'.
System.MissingMethodException: Method not found: 'System.ReadOnlySpan`1<Char> Microsoft.IO.Path.GetFileName(System.ReadOnlySpan`1<Char>)'.
   at Microsoft.Build.Shared.FileMatcher.IsFileNameMatch(String path, String pattern)
   at System.Linq.Enumerable.WhereListIterator`1.MoveNext()
   at Microsoft.Build.Shared.FileMatcher.<RemoveProjectDirectory>d__37.MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at Microsoft.Build.Shared.FileMatcher.GetFilesForStep(RecursiveStepResult stepResult, RecursionState recursionState, String projectDirectory, Boolean stripProjectDirectory)
   at Microsoft.Build.Shared.FileMatcher.GetFilesRecursive(ConcurrentStack`1 listOfFiles, RecursionState recursionState, String projectDirectory, Boolean stripProjectDirectory, IList`1 searchesToExclude, Dictionary`2 searchesToExcludeInSubdirs, TaskOptions taskOptions)
   at Microsoft.Build.Shared.FileMatcher.GetFilesImplementation(String projectDirectoryUnescaped, String filespecUnescaped, List`1 excludeSpecsUnescaped)
   at Microsoft.Build.Shared.FileMatcher.<>c__DisplayClass67_0.<GetFiles>b__1(String _)
   at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory)
   at Microsoft.Build.Shared.FileMatcher.GetFiles(String projectDirectoryUnescaped, String filespecUnescaped, List`1 excludeSpecsUnescaped)
   at Microsoft.Build.Internal.EngineFileUtilities.GetFileList(String directoryEscaped, String filespecEscaped, Boolean returnEscaped, Boolean forceEvaluateWildCards, IEnumerable`1 excludeSpecsEscaped, FileMatcher fileMatcher, Object loggingMechanism, IElementLocation includeLocation, IElementLocation excludeLocation, IElementLocation importLocation, BuildEventContext buildEventContext, String buildEventFileInfoFullPath, Boolean disableExcludeDriveEnumerationWarning)
   at Microsoft.Build.Evaluation.LazyItemEvaluator`4.IncludeOperation.SelectItems(Builder listBuilder, ImmutableHashSet`1 globsToIgnore)
   at Microsoft.Build.Evaluation.LazyItemEvaluator`4.LazyItemOperation.ApplyImpl(Builder listBuilder, ImmutableHashSet`1 globsToIgnore)
   at Microsoft.Build.Evaluation.LazyItemEvaluator`4.LazyItemOperation.Apply(Builder listBuilder, ImmutableHashSet`1 globsToIgnore)
   at Microsoft.Build.Evaluation.LazyItemEvaluator`4.LazyItemList.ComputeItems(LazyItemList lazyItemList, ImmutableHashSet`1 globsToIgnore)
   at Microsoft.Build.Evaluation.LazyItemEvaluator`4.LazyItemList.GetItemData(ImmutableHashSet`1 globsToIgnore)
   at Microsoft.Build.Evaluation.LazyItemEvaluator`4.LazyItemList.GetMatchedItems(ImmutableHashSet`1 globsToIgnore)
   at Microsoft.Build.Evaluation.LazyItemEvaluator`4.EvaluatorData.GetItems(String itemType)
   at Microsoft.Build.Evaluation.Expander`2.ItemExpander.ExpandExpressionCapture[S](Expander`2 expander, ItemExpressionCapture expressionCapture, IItemProvider`1 evaluatedItems, IElementLocation elementLocation, ExpanderOptions options, Boolean includeNullEntries, Boolean& isTransformExpression, List`1& itemsFromCapture)
   at Microsoft.Build.Evaluation.Expander`2.ItemExpander.ExpandExpressionCaptureIntoStringBuilder[S](Expander`2 expander, ItemExpressionCapture capture, IItemProvider`1 evaluatedItems, IElementLocation elementLocation, SpanBasedStringBuilder builder, ExpanderOptions options)
   at Microsoft.Build.Evaluation.Expander`2.ItemExpander.ExpandItemVectorsIntoString[T](Expander`2 expander, String expression, IItemProvider`1 items, ExpanderOptions options, IElementLocation elementLocation)
   at Microsoft.Build.Evaluation.Expander`2.ExpandIntoStringLeaveEscaped(String expression, ExpanderOptions options, IElementLocation elementLocation)
   at Microsoft.Build.Evaluation.ConditionEvaluator.ConditionEvaluationState`2.ExpandIntoStringBreakEarly(String expression)
   at Microsoft.Build.Evaluation.StringExpressionNode.EvaluatesToEmpty(IConditionEvaluationState state)
   at Microsoft.Build.Evaluation.MultipleComparisonNode.BoolEvaluate(IConditionEvaluationState state)
   at Microsoft.Build.Evaluation.OperatorExpressionNode.TryBoolEvaluate(IConditionEvaluationState state, Boolean& result)
   at Microsoft.Build.Evaluation.OrExpressionNode.BoolEvaluate(IConditionEvaluationState state)
   at Microsoft.Build.Evaluation.OperatorExpressionNode.TryBoolEvaluate(IConditionEvaluationState state, Boolean& result)
   at Microsoft.Build.Evaluation.OrExpressionNode.BoolEvaluate(IConditionEvaluationState state)
   at Microsoft.Build.Evaluation.OperatorExpressionNode.TryBoolEvaluate(IConditionEvaluationState state, Boolean& result)
   at Microsoft.Build.Evaluation.OrExpressionNode.BoolEvaluate(IConditionEvaluationState state)
   at Microsoft.Build.Evaluation.OperatorExpressionNode.TryBoolEvaluate(IConditionEvaluationState state, Boolean& result)
   at Microsoft.Build.Evaluation.OrExpressionNode.BoolEvaluate(IConditionEvaluationState state)
   at Microsoft.Build.Evaluation.OperatorExpressionNode.TryBoolEvaluate(IConditionEvaluationState state, Boolean& result)
   at Microsoft.Build.Evaluation.GenericExpressionNode.Evaluate(IConditionEvaluationState state)
   at Microsoft.Build.Evaluation.ConditionEvaluator.EvaluateConditionCollectingConditionedProperties[P,I](String condition, ParserOptions options, Expander`2 expander, ExpanderOptions expanderOptions, Dictionary`2 conditionedPropertiesTable, String evaluationDirectory, ElementLocation elementLocation, IFileSystem fileSystem, LoggingContext loggingContext, ProjectRootElementCacheBase projectRootElementCache)
   at Microsoft.Build.Evaluation.ConditionEvaluator.EvaluateCondition[P,I](String condition, ParserOptions options, Expander`2 expander, ExpanderOptions expanderOptions, String evaluationDirectory, ElementLocation elementLocation, IFileSystem fileSystem, LoggingContext loggingContext, ProjectRootElementCacheBase projectRootElementCache)
   at Microsoft.Build.Evaluation.LazyItemEvaluator`4.EvaluateCondition(String condition, ProjectElement element, ExpanderOptions expanderOptions, ParserOptions parserOptions, Expander`2 expander, LazyItemEvaluator`4 lazyEvaluator)
   at Microsoft.Build.Evaluation.LazyItemEvaluator`4.EvaluateConditionWithCurrentState(ProjectElement element, ExpanderOptions expanderOptions, ParserOptions parserOptions)
   at Microsoft.Build.Evaluation.Evaluator`4.EvaluateItemElement(Boolean itemGroupConditionResult, ProjectItemElement itemElement, LazyItemEvaluator`4 lazyEvaluator)
   at Microsoft.Build.Evaluation.Evaluator`4.EvaluateItemGroupElement(ProjectItemGroupElement itemGroupElement, LazyItemEvaluator`4 lazyEvaluator)
   at Microsoft.Build.Evaluation.Evaluator`4.Evaluate()
   at Microsoft.Build.Evaluation.Evaluator`4.Evaluate(IEvaluatorData`4 data, Project project, ProjectRootElement root, ProjectLoadSettings loadSettings, Int32 maxNodeCount, PropertyDictionary`1 environmentProperties, ICollection`1 propertiesFromCommandLine, ILoggingService loggingService, IItemFactory`2 itemFactory, IToolsetProvider toolsetProvider, IDirectoryCacheFactory directoryCacheFactory, ProjectRootElementCacheBase projectRootElementCache, BuildEventContext buildEventContext, ISdkResolverService sdkResolverService, Int32 submissionId, EvaluationContext evaluationContext, Boolean interactive)
   at Microsoft.Build.Evaluation.Project.ProjectImpl.Reevaluate(ILoggingService loggingServiceForEvaluation, ProjectLoadSettings loadSettings, EvaluationContext evaluationContext)
   at Microsoft.Build.Evaluation.Project.ProjectImpl.ReevaluateIfNecessary(ILoggingService loggingServiceForEvaluation, ProjectLoadSettings loadSettings, EvaluationContext evaluationContext)
   at Microsoft.Build.Evaluation.Project.ProjectImpl.ReevaluateIfNecessary(EvaluationContext evaluationContext)
   at Microsoft.Build.Evaluation.Project.ProjectImpl.Initialize(IDictionary`2 globalProperties, String toolsVersion, String subToolsetVersion, ProjectLoadSettings loadSettings, EvaluationContext evaluationContext, Boolean interactive)
   at Microsoft.Build.Evaluation.Project..ctor(String projectFile, IDictionary`2 globalProperties, String toolsVersion, String subToolsetVersion, ProjectCollection projectCollection, ProjectLoadSettings loadSettings, EvaluationContext evaluationContext, IDirectoryCacheFactory directoryCacheFactory, Boolean interactive)
   at Microsoft.Build.Evaluation.ProjectCollection.LoadProject(String fileName, IDictionary`2 globalProperties, String toolsVersion)
   at OmniSharp.MSBuild.ProjectLoader.EvaluateProjectFileCore(String filePath, IReadOnlyDictionary`2 projectConfigurationsInSolution, IList`1 loggers) in D:\\a\\1\\s\\src\\OmniSharp.MSBuild\\ProjectLoader.cs:line 160
   at OmniSharp.MSBuild.ProjectLoader.BuildProject(String filePath, IReadOnlyDictionary`2 configurationsInSolution) in D:\\a\\1\\s\\src\\OmniSharp.MSBuild\\ProjectLoader.cs:line 84
   at OmniSharp.MSBuild.ProjectFile.ProjectFileInfo.Load(String filePath, ProjectIdInfo projectIdInfo, ProjectLoader loader, Guid sessionId, DotNetInfo dotNetInfo) in D:\\a\\1\\s\\src\\OmniSharp.MSBuild\\ProjectFile\\ProjectFileInfo.cs:line 117
   at OmniSharp.MSBuild.ProjectManager.<>c__DisplayClass32_0.<LoadProject>b__0() in D:\\a\\1\\s\\src\\OmniSharp.MSBuild\\ProjectManager.cs:line 305
   at OmniSharp.MSBuild.ProjectManager.LoadOrReloadProject(String projectFilePath, Func`1 loader) in D:\\a\\1\\s\\src\\OmniSharp.MSBuild\\ProjectManager.cs:line 316

[akarel-mb]

Quick update, the omnisharp-net.6.0 build works as expected. So it's just the legacy build that is affected.

[BakeryD]

Quick update, the omnisharp-net.6.0 build works as expected. So it's just the legacy build that is affected.

So the legacy build is bricked if you have .NET 9 installed on your machine?

[akarel-mb]

Yes. It's happened before with the v7 to v8 dotnet update too. The framework (legacy) version doesn't handle the change, where the net6 version just uses the locally installed framework, so there are no issues. There is another old thread related to this as well and, if memory serves, it explained the why, but it is lost deep in my history (possibly on a different browser) and I couldn't find it.

I'm assuming it is related to target compilation with the framework version and expected paths for build and props, etc. 🤷