Reconfigure Legacy MSBuildReferenceResolver to be API-driven (#6898)

* Don't expose Legacy MSBuildReferenceResolver

* Move the files boss hoss

* Remove unused opens

* Fix tests

* oopsie doopsie

* Do it better

* fix

* Fix FCS

Author: cartermp

fcs/FSharp.Compiler.Service.MSBuild.v12/FSharp.Compiler.Service.MSBuild.v12.fsproj

@@ -17,7 +17,7 @@
     <PackageTags>F#, compiler, msbuild</PackageTags>
   </PropertyGroup>
   <ItemGroup>
-    <Compile Include="..\..\src\fsharp\MSBuildReferenceResolver.fs">
+    <Compile Include="$(FSharpSourcesRoot)\fsharp\LegacyMSBuildReferenceResolver.fs">
       <Link>Service/MSBuildReferenceResolver.fs</Link>
     </Compile>
   </ItemGroup>

fcs/FSharp.Compiler.Service/FSharp.Compiler.Service.fsproj

@@ -187,9 +187,6 @@
     <Compile Include="$(FSharpSourcesRoot)/fsharp/ErrorResolutionHints.fs">
       <Link>ErrorLogging/ErrorResolutionHints.fs</Link>
     </Compile>
-    <Compile Include="$(FSharpSourcesRoot)/fsharp/ReferenceResolver.fs">
-      <Link>ReferenceResolution/ReferenceResolver.fs</Link>
-    </Compile>
     <FsLex Include="$(FSharpSourcesRoot)\absil\illex.fsl">
       <OtherFlags>--unicode --lexlib Internal.Utilities.Text.Lexing</OtherFlags>
       <Link>AbsIL/illex.fsl</Link>
@@ -270,6 +267,12 @@
     <Compile Include="$(FSharpSourcesRoot)/absil/ilreflect.fs">
       <Link>AbsIL/ilreflect.fs</Link>
     </Compile>
+    <Compile Include="$(FSharpSourcesRoot)/fsharp/ReferenceResolver.fs">
+      <Link>ReferenceResolution/ReferenceResolver.fs</Link>
+    </Compile>
+    <Compile Include="$(FSharpSourcesRoot)\fsharp\SimulatedMSBuildReferenceResolver.fs">
+      <Link>ReferenceResolution/SimulatedMSBuildReferenceResolver.fs</Link>
+    </Compile>
     <Compile Include="$(FSharpSourcesRoot)/utils/CompilerLocationUtils.fs">
       <Link>CompilerLocation/CompilerLocationUtils.fs</Link>
     </Compile>
@@ -591,9 +594,6 @@
     <Compile Include="$(FSharpSourcesRoot)\utils\reshapedmsbuild.fs">
       <Link>Service/reshapedmsbuild.fs</Link>
     </Compile>
-    <Compile Include="$(FSharpSourcesRoot)\fsharp\SimulatedMSBuildReferenceResolver.fs">
-      <Link>Service/SimulatedMSBuildReferenceResolver.fs</Link>
-    </Compile>
     <Compile Include="$(FSharpSourcesRoot)\fsharp\service\ServiceDeclarationLists.fsi">
       <Link>Service/ServiceDeclarationLists.fsi</Link>
     </Compile>

src/fsharp/MSBuildReferenceResolver.fs …fsharp/LegacyMSBuildReferenceResolver.fssrc/fsharp/MSBuildReferenceResolver.fs renamed to src/fsharp/LegacyMSBuildReferenceResolver.fs src/fsharp/MSBuildReferenceResolver.fs renamed to src/fsharp/LegacyMSBuildReferenceResolver.fs

@@ -1,6 +1,6 @@
 // Copyright (c) Microsoft Corporation.  All Rights Reserved.  See License.txt in the project root for license information.
 
-module internal FSharp.Compiler.MSBuildReferenceResolver 
+module LegacyMSBuildReferenceResolver
 
     open System
     open System.IO
@@ -16,6 +16,7 @@ module internal FSharp.Compiler.MSBuildReferenceResolver
     open Microsoft.Build.Tasks
     open Microsoft.Build.Utilities
     open Microsoft.Build.Framework
+    open FSharp.Compiler
 
     // Reflection wrapper for properties
     type System.Object with
@@ -367,7 +368,7 @@ module internal FSharp.Compiler.MSBuildReferenceResolver
 
         resolvedFiles
 
-    let Resolver =
+    let getResolver () =
        { new ReferenceResolver.Resolver with 
            member __.HighestInstalledNetFrameworkVersion() = HighestInstalledRefAssembliesOrDotNETFramework()
            member __.DotNetFrameworkReferenceAssembliesRootDirectory =  DotNetFrameworkReferenceAssembliesRootDirectory

src/fsharp/LegacyMSBuildReferenceResolver.fsi

@@ -0,0 +1,6 @@
+// Copyright (c) Microsoft Corporation.  All Rights Reserved.  See License.txt in the project root for license information.
+module LegacyMSBuildReferenceResolver
+
+open FSharp.Compiler
+
+val getResolver: unit -> ReferenceResolver.Resolver

src/fsharp/fscmain.fs

@@ -62,7 +62,7 @@ module Driver =
 #if CROSS_PLATFORM_COMPILER
             SimulatedMSBuildReferenceResolver.SimulatedMSBuildResolver
 #else
-            MSBuildReferenceResolver.Resolver
+            LegacyMSBuildReferenceResolver.getResolver()
 #endif
 
         // This is the only place where ReduceMemoryFlag.No is set. This is because fsc.exe is not a long-running process and

src/fsharp/fsi/fsimain.fs

@@ -228,7 +228,7 @@ let evaluateSession(argv: string[]) =
 #if CROSS_PLATFORM_COMPILER
             SimulatedMSBuildReferenceResolver.SimulatedMSBuildResolver
 #else
-            MSBuildReferenceResolver.Resolver
+            LegacyMSBuildReferenceResolver.getResolver()
 #endif
         // Update the configuration to include 'StartServer', WinFormsEventLoop and 'GetOptionalConsoleReadLine()'
         let rec fsiConfig = 

src/fsharp/service/service.fs

@@ -2945,9 +2945,9 @@ type FSharpChecker(legacyReferenceResolver, projectCacheSize, keepAssemblyConten
     static member Create(?projectCacheSize, ?keepAssemblyContents, ?keepAllBackgroundResolutions, ?legacyReferenceResolver, ?tryGetMetadataSnapshot, ?suggestNamesForErrors) = 
 
         let legacyReferenceResolver = 
-            match legacyReferenceResolver with 
-            | None -> SimulatedMSBuildReferenceResolver.GetBestAvailableResolver()
+            match legacyReferenceResolver with
             | Some rr -> rr
+            | None -> SimulatedMSBuildReferenceResolver.GetBestAvailableResolver()
 
         let keepAssemblyContents = defaultArg keepAssemblyContents false
         let keepAllBackgroundResolutions = defaultArg keepAllBackgroundResolutions true