fire events when script host resolves assembly reference (#7571)

* add event every time `#r` is invoked

* pass additional args to script host

Author: brettfo

src/fsharp/CompileOps.fs

@@ -4775,7 +4775,7 @@ and [<Sealed>] TcImports(tcConfigP: TcConfigProvider, initialResolutions: TcAsse
 
 /// Process #r in F# Interactive.
 /// Adds the reference to the tcImports and add the ccu to the type checking environment.
-let RequireDLL (ctok, tcImports: TcImports, tcEnv, thisAssemblyName, m, file) = 
+let RequireDLL (ctok, tcImports: TcImports, tcEnv, thisAssemblyName, m, file, assemblyReferenceAdded: string -> unit) =
     let resolutions = CommitOperationResult(tcImports.TryResolveAssemblyReference(ctok, AssemblyReference(m, file, None), ResolveAssemblyReferenceMode.ReportErrors))
     let dllinfos, ccuinfos = tcImports.RegisterAndImportReferencedAssemblies(ctok, resolutions) |> Cancellable.runWithoutCancellation
 
@@ -4786,7 +4786,13 @@ let RequireDLL (ctok, tcImports: TcImports, tcEnv, thisAssemblyName, m, file) =
 
     let g = tcImports.GetTcGlobals()
     let amap = tcImports.GetImportMap()
-    let tcEnv = (tcEnv, asms) ||> List.fold (fun tcEnv asm -> AddCcuToTcEnv(g, amap, m, tcEnv, thisAssemblyName, asm.FSharpViewOfMetadata, asm.AssemblyAutoOpenAttributes, asm.AssemblyInternalsVisibleToAttributes)) 
+    let buildTcEnv tcEnv asm =
+        let tcEnv = AddCcuToTcEnv(g, amap, m, tcEnv, thisAssemblyName, asm.FSharpViewOfMetadata, asm.AssemblyAutoOpenAttributes, asm.AssemblyInternalsVisibleToAttributes)
+        match asm.FSharpViewOfMetadata.FileName with
+        | Some asmPath -> assemblyReferenceAdded asmPath
+        | None -> ()
+        tcEnv
+    let tcEnv = (tcEnv, asms) ||> List.fold buildTcEnv
     tcEnv, (dllinfos, asms)
 
 

src/fsharp/CompileOps.fsi

@@ -672,7 +672,7 @@ val WriteOptimizationData: TcGlobals * filename: string * inMem: bool * CcuThunk
 
 /// Process #r in F# Interactive.
 /// Adds the reference to the tcImports and add the ccu to the type checking environment.
-val RequireDLL: CompilationThreadToken * TcImports * TcEnv * thisAssemblyName: string * referenceRange: range * file: string -> TcEnv * (ImportedBinary list * ImportedAssembly list)
+val RequireDLL: CompilationThreadToken * TcImports * TcEnv * thisAssemblyName: string * referenceRange: range * file: string * assemblyReferenceAdded: (string -> unit) -> TcEnv * (ImportedBinary list * ImportedAssembly list)
 
 /// Processing # commands
 val ProcessMetaCommandsFromInput: 

src/fsharp/fsi/fsi.fs

@@ -962,6 +962,8 @@ type internal FsiDynamicCompiler
     let outfile = "TMPFSCI.exe"
     let assemblyName = "FSI-ASSEMBLY"
 
+    let assemblyReferenceAddedEvent = Control.Event<string>()
+
     let mutable fragmentId = 0
     let mutable prevIt : ValRef option = None
 
@@ -1245,7 +1247,7 @@ type internal FsiDynamicCompiler
         let tcState = istate.tcState 
         let tcEnv,(_dllinfos,ccuinfos) = 
             try
-                RequireDLL (ctok, tcImports, tcState.TcEnvFromImpls, assemblyName, m, path)
+                RequireDLL (ctok, tcImports, tcState.TcEnvFromImpls, assemblyName, m, path, assemblyReferenceAddedEvent.Trigger)
             with e ->
                 tcConfigB.RemoveReferencedAssemblyByPath(m,path)
                 reraise()
@@ -1334,6 +1336,8 @@ type internal FsiDynamicCompiler
     member __.FormatValue(obj:obj, objTy) = 
         valuePrinter.FormatValue(obj, objTy)
 
+    member __.AssemblyReferenceAdded = assemblyReferenceAddedEvent.Publish
+
 //----------------------------------------------------------------------------
 // ctrl-c handling
 //----------------------------------------------------------------------------
@@ -2640,6 +2644,9 @@ type FsiEvaluationSession (fsi: FsiEvaluationSessionHostConfig, argv:string[], i
         fsiInteractionProcessor.EvalScript(ctok, scriptPath, errorLogger)
         |> commitResultNonThrowing errorOptions scriptPath errorLogger
         |> function Choice1Of2 (_), errs -> Choice1Of2 (), errs | Choice2Of2 exn, errs -> Choice2Of2 exn, errs
+
+    /// Event fires every time an assembly reference is added to the execution environment, e.g., via `#r`.
+    member __.AssemblyReferenceAdded = fsiDynamicCompiler.AssemblyReferenceAdded
 
     /// Performs these steps:
     ///    - Load the dummy interaction, if any

src/fsharp/fsi/fsi.fsi

@@ -227,6 +227,9 @@ type FsiEvaluationSession =
     /// A host calls this to report an unhandled exception in a standard way, e.g. an exception on the GUI thread gets printed to stderr
     member ReportUnhandledException : exn: exn -> unit
 
+    /// Event fires every time an assembly reference is added to the execution environment, e.g., via `#r`.
+    member AssemblyReferenceAdded : IEvent<string>
+
     /// Load the dummy interaction, load the initial files, and,
     /// if interacting, start the background thread to read the standard input.
     ///