Compiler fix and tests (#8803)

src/fsharp/CompileOps.fs

@@ -5008,9 +5008,6 @@ let ProcessMetaCommandsFromInput
                     let output = tcConfig.outputDir |> Option.defaultValue ""
                     let dm = tcConfig.dependencyProvider.TryFindDependencyManagerInPath(tcConfig.compilerToolPaths, output , reportError, path)
                     match dm with
-                    | dllpath, null when String.IsNullOrWhiteSpace(dllpath) ->
-                        state           // error already reported
-
                     | _, dependencyManager when not(isNull dependencyManager) ->
                         if tcConfig.langVersion.SupportsFeature(LanguageFeature.PackageManagement) then
                             packageRequireF state (dependencyManager, m, path)
@@ -5020,7 +5017,11 @@ let ProcessMetaCommandsFromInput
 
                     // #r "Assembly"
                     | path, _ ->
-                        dllRequireF state (m, path)
+                        let p =
+                            if String.IsNullOrWhiteSpace(path) then ""
+                            else path
+
+                        dllRequireF state (m, p)
 
                 | _ ->
                    errorR(Error(FSComp.SR.buildInvalidHashrDirective(), m))

tests/fsharp/Compiler/Language/CompilerDirectiveTests.fs

+// Copyright (c) Microsoft Corporation.  All Rights Reserved.  See License.txt in the project root for license information.
+
+namespace FSharp.Compiler.UnitTests
+
+open NUnit.Framework
+open FSharp.Compiler.SourceCodeServices
+
+[<TestFixture>]
+module ``Test Compiler Directives`` =
+
+    [<Test>]
+    let ``compiler #r "" is invalid``() =
+        let source = """
+#r ""
+"""
+        CompilerAssert.CompileWithErrors(
+            Compilation.Create(source, Fsx, Library),
+            [|
+                FSharpErrorSeverity.Warning, 213, (2,1,2,6), "'' is not a valid assembly name"
+            |])
+
+    [<Test>]
+    let ``compiler #r "   " is invalid``() =
+        let source = """
+#r "    "
+"""
+        CompilerAssert.CompileWithErrors(
+            Compilation.Create(source, Fsx, Library),
+            [|
+                FSharpErrorSeverity.Warning, 213, (2,1,2,10), "'' is not a valid assembly name"
+            |])

tests/fsharp/FSharpSuite.Tests.fsproj

@@ -60,6 +60,7 @@
     <Compile Include="Compiler\Warnings\ExperimentalAttributeTests.fs" />
     <Compile Include="Compiler\Warnings\PatternMatchingWarningTests.fs" />
     <Compile Include="Compiler\SourceTextTests.fs" />
+    <Compile Include="Compiler\Language\CompilerDirectiveTests.fs" />
     <Compile Include="Compiler\Language\DefaultInterfaceMemberTests.fs" />
     <Compile Include="Compiler\Language\OptionalInteropTests.fs" />
     <Compile Include="Compiler\Language\UIntTests.fs" />