Cache C# Compilation Emit by Project Version to avoid excessive background churn - #20119
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xperiandri wants to merge 3 commits into
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Cache C# Compilation Emit by Project Version to avoid excessive background churn#20119xperiandri wants to merge 3 commits into
xperiandri wants to merge 3 commits into
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- Add ActiveDocumentDetection module (IVsMonitorSelection-based helper) - Gate UnusedDeclarationsAnalyzer to active document - Gate SimplifyNameDiagnosticAnalyzer to active document - Gate FSharpInlayHintsService to active document - Gate UnusedOpensDiagnosticAnalyzer to active document - Add ActiveDocumentDetection.fs to FSharp.Editor.fsproj Fixes dotnet#20114
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🔍 Tooling Safety Check — Affects-Build-Infra, Affects-Restore, Affects-Agent-Config, Scope-Review-Needed
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Fixes #20118.
Description
When C# projects change, Roslyn creates new
Compilationinstances. The F# IDE integration currently uses aConditionalWeakTableto cache the emitted PE reference from these compilations. Because newCompilationobjects are continually created by Roslyn, the weak table cache misses, causing repeated, expensive metadata-only emissions (Compilation.Emit(metadataOnly=true)). This contributes to UI latency and background CPU churn.Solution
This PR adds an
emitCache: ConcurrentDictionary<ProjectId, ConcurrentDictionary<VersionStamp, FSharpReferencedProject>>toFSharpProjectOptionsManager.fs.This allows caching based on a stable identifier (
projectIdandproject.Version), avoiding unnecessary re-emission of assemblies when the underlying C# project hasn't functionally changed. The cache properly invalidates and handlesCancellationTokenviacancellableTask { ... }.