Rename activity file, fix NRE, rename start methods

src/Compiler/Driver/CompilerOptions.fs

@@ -2386,7 +2386,7 @@ let ReportTime (tcConfig: TcConfig) descr =
 
         tPrev <- Some(tStart, tNow, utNow, gcNow)
 
-    nPrev <- Some(descr, Activity.StartNoTags descr)
+    nPrev <- Some(descr, Activity.startNoTags descr)
 
 let ignoreFailureOnMono1_1_16 f =
     try

src/Compiler/FSharp.Compiler.Service.fsproj

@@ -133,8 +133,8 @@
     <Compile Include="Utilities\range.fsi" />
     <Compile Include="Utilities\range.fs" />
     <EmbeddedText Include="Facilities\UtilsStrings.txt" />
-    <Compile Include="Facilities\Logger.fsi" />
-    <Compile Include="Facilities\Logger.fs" />
+    <Compile Include="Facilities\Activity.fsi" />
+    <Compile Include="Facilities\Activity.fs" />
     <Compile Include="Facilities\LanguageFeatures.fsi" />
     <Compile Include="Facilities\LanguageFeatures.fs" />
     <Compile Include="Facilities\DiagnosticOptions.fsi" />

src/Compiler/Facilities/Activity.fs

@@ -0,0 +1,29 @@
+// Copyright (c) Microsoft Corporation.  All Rights Reserved.  See License.txt in the project root for license information.
+
+namespace FSharp.Compiler.Diagnostics
+
+open System
+open System.Diagnostics
+
+[<RequireQualifiedAccess>]
+module Activity =    
+
+    let private dummyDisposable =
+        {
+            new IDisposable with 
+                member this.Dispose() = ()
+        }
+
+    let private activitySourceName = "fsc"
+    let private activitySource = new ActivitySource(activitySourceName)
+
+    let start name (tags : (string * string) seq) : IDisposable = 
+        match activitySource.StartActivity(name) |> Option.ofObj with
+        | Some activity ->
+            for key, value in tags do
+                activity.AddTag(key, value) |> ignore
+            activity :> IDisposable
+        | None ->
+            dummyDisposable
+
+    let startNoTags name: IDisposable = activitySource.StartActivity(name)

src/Compiler/Facilities/Logger.fsi → src/Compiler/Facilities/Activity.fsi

@@ -3,13 +3,12 @@
 namespace FSharp.Compiler.Diagnostics
 
 open System
-open System.Diagnostics
 
 /// For activities following the dotnet distributed tracing concept
 /// https://learn.microsoft.com/en-us/dotnet/core/diagnostics/distributed-tracing-concepts?source=recommendations
 [<RequireQualifiedAccess>]
 module internal Activity =
 
-    val StartNoTags: name: string -> IDisposable
+    val startNoTags: name: string -> IDisposable
 
-    val Start: name: string -> tags: (string * string) seq -> IDisposable
+    val start: name: string -> tags: (string * string) seq -> IDisposable

src/Compiler/Service/service.fs

@@ -1137,7 +1137,7 @@ type BackgroundCompiler
     member _.ProjectChecked = projectChecked.Publish
 
     member _.ClearCaches() =
-        use _ = Activity.StartNoTags "BackgroundCompiler.ClearCaches"
+        use _ = Activity.startNoTags "BackgroundCompiler.ClearCaches"
 
         lock gate (fun () ->
             parseCacheLock.AcquireLock(fun ltok ->
@@ -1149,7 +1149,7 @@ type BackgroundCompiler
             scriptClosureCache.Clear AnyCallerThread)
 
     member _.DownsizeCaches() =
-        use _ = Activity.StartNoTags "BackgroundCompiler.DownsizeCaches"
+        use _ = Activity.startNoTags "BackgroundCompiler.DownsizeCaches"
 
         lock gate (fun () ->
             parseCacheLock.AcquireLock(fun ltok ->
@@ -1241,7 +1241,7 @@ type FSharpChecker
             ?parallelReferenceResolution
         ) =
 
-        use _ = Activity.StartNoTags "FSharpChecker.Create"
+        use _ = Activity.startNoTags "FSharpChecker.Create"
 
         let legacyReferenceResolver =
             match legacyReferenceResolver with
@@ -1356,7 +1356,7 @@ type FSharpChecker
     // This is for unit testing only
     member ic.ClearLanguageServiceRootCachesAndCollectAndFinalizeAllTransients() =
         use _ =
-            Activity.StartNoTags "FsharpChecker.ClearLanguageServiceRootCachesAndCollectAndFinalizeAllTransients"
+            Activity.startNoTags "FsharpChecker.ClearLanguageServiceRootCachesAndCollectAndFinalizeAllTransients"
 
         ic.ClearCaches()
         GC.Collect()