* feat(FSharp.Editor.Tests): add AsyncBugReproduction.fs to test suite

* fix(AddExplicitReturnType.fs): remove unnecessary assertion
* fix(RefactorTestFramework.fs): convert symbols sequence to list

Author: SebastianAtWork

vsintegration/tests/FSharp.Editor.Tests/FSharp.Editor.Tests.fsproj

@@ -73,6 +73,7 @@
     <Compile Include="Refactors\RefactorTestFramework.fs" />
     <Compile Include="Refactors\AddExplicitReturnType.fs" />
     <Compile Include="Refactors\RemoveExplicitReturnType.fs" />
+    <Compile Include="Refactors\AsyncBugReproduction.fs" />
     <Compile Include="Hints\HintTestFramework.fs" />
     <Compile Include="Hints\OptionParserTests.fs" />
     <Compile Include="Hints\InlineParameterNameHintTests.fs" />

vsintegration/tests/FSharp.Editor.Tests/Refactors/AddExplicitReturnType.fs

@@ -91,7 +91,7 @@ let ``Infer explicit return type`` (functionHeader: string) (returnType: string)
         let spanStart = code.IndexOf(symbolName)
 
         let! newDoc = tryRefactor code spanStart context (new AddExplicitReturnType())
-        do Assert.NotNull(code)
+
         do! AssertHasSpecificExplicitReturnType symbolName returnType newDoc context.CT
     }
 

vsintegration/tests/FSharp.Editor.Tests/Refactors/AsyncBugReproduction.fs

@@ -0,0 +1,77 @@
+module FSharp.Editor.Tests.Refactors.AsyncBugReproduction
+
+open Microsoft.VisualStudio.FSharp.Editor
+open Xunit
+open System
+open System.Collections.Immutable
+open System.Text.RegularExpressions
+
+open Microsoft.CodeAnalysis
+open Microsoft.CodeAnalysis.CodeFixes
+open Microsoft.CodeAnalysis.Text
+open Microsoft.VisualStudio.FSharp.Editor
+open Microsoft.VisualStudio.FSharp.Editor.CancellableTasks
+
+open FSharp.Compiler.Diagnostics
+open FSharp.Editor.Tests.Helpers
+
+open Microsoft.CodeAnalysis.CodeRefactorings
+open NUnit.Framework
+open Microsoft.CodeAnalysis.CodeActions
+open System.Collections.Generic
+open Microsoft.VisualStudio.LanguageServices
+open FSharp.Editor.Tests.Refactors.RefactorTestFramework
+open Microsoft.Build.Utilities
+open System.Threading
+open FSharp.Test.ReflectionHelper
+open Microsoft.Build.Utilities
+open FSharp.Test.ProjectGeneration.ProjectOperations
+open FSharp.Compiler.Symbols
+open Xunit
+open System.Runtime.InteropServices
+
+[<Theory>]
+[<InlineData("(a:float) (b:int)", "float")>]
+[<InlineData("(a:float) (b:int)", "float")>]
+let ``Reproducing code null spanStart Bug`` (functionHeader: string) (returnType: string) =
+    task {
+
+        let symbolName = "sum"
+
+        let code =
+            $"""
+            let sum {functionHeader}= a + b
+            """
+
+        use context = TestContext.CreateWithCode code
+
+        let spanStart = code.IndexOf(symbolName)
+
+        let! newDoc = tryRefactor code spanStart context (new AddExplicitReturnType())
+
+        do! AssertHasSpecificExplicitReturnType symbolName returnType newDoc context.CT
+    }
+
+[<Theory>]
+[<InlineData("(a:float) (b:int)", "float")>]
+[<InlineData("(a:float) (b:int)", "float")>]
+let ``But works when not async`` (functionHeader: string) (returnType: string) =
+
+    let symbolName = "sum"
+
+    let code =
+        $"""
+        let sum {functionHeader}= a + b
+        """
+
+    use context = TestContext.CreateWithCode code
+
+    let spanStart = code.IndexOf(symbolName)
+
+    let newDocTask = tryRefactor code spanStart context (new AddExplicitReturnType())
+    let newDoc = newDocTask.GetAwaiter().GetResult()
+
+    let assertTask =
+        AssertHasSpecificExplicitReturnType symbolName returnType newDoc context.CT
+
+    do assertTask.GetAwaiter().GetResult()

vsintegration/tests/FSharp.Editor.Tests/Refactors/RefactorTestFramework.fs

@@ -47,7 +47,7 @@ let GetReturnTypeOfSymbol (symbolName: string) (document: Document) ct =
             document.GetFSharpParseAndCheckResultsAsync symbolName
             |> CancellableTask.start ct
 
-        let symbols = checkFileResults.GetAllUsesOfAllSymbolsInFile ct
+        let symbols = checkFileResults.GetAllUsesOfAllSymbolsInFile ct |> List.ofSeq
         let symbolUse = symbols |> Seq.find (fun s -> s.Symbol.DisplayName = symbolName)
 
         return