Refactor Go to Definition service (#2855)

* cleanup

* refactor GoToDefinitionService

* incorporate @majocha's PR #2856

vsintegration/tests/unittests/GoToDefinitionServiceTests.fs

@@ -23,26 +23,47 @@ namespace Microsoft.VisualStudio.FSharp.Editor.Tests.Roslyn
 
 open System
 open System.IO
-open System.Threading
-open System.Linq
-
 open NUnit.Framework
 
 open Microsoft.CodeAnalysis
-open Microsoft.CodeAnalysis.Completion
-open Microsoft.CodeAnalysis.Classification
 open Microsoft.CodeAnalysis.Text
 open Microsoft.VisualStudio.FSharp.Editor
 
-open Microsoft.VisualStudio.FSharp.Editor
-open Microsoft.VisualStudio.FSharp.LanguageService
-
 open Microsoft.FSharp.Compiler.SourceCodeServices
 open Microsoft.FSharp.Compiler.Range
 
 [<TestFixture>][<Category "Roslyn Services">]
 module GoToDefinitionServiceTests =
 
+    let private findDefinition
+        (
+            checker: FSharpChecker, 
+            documentKey: DocumentId, 
+            sourceText: SourceText, 
+            filePath: string, 
+            position: int,
+            defines: string list, 
+            options: FSharpProjectOptions, 
+            textVersionHash: int
+        ) : range option = 
+        maybe {
+            let textLine = sourceText.Lines.GetLineFromPosition position
+            let textLinePos = sourceText.Lines.GetLinePosition position
+            let fcsTextLineNumber = Line.fromZ textLinePos.Line
+            let! lexerSymbol = Tokenizer.getSymbolAtPosition(documentKey, sourceText, position, filePath, defines, SymbolLookupKind.Greedy, false)
+            let! _, _, checkFileResults = 
+                checker.ParseAndCheckDocument 
+                    (filePath, textVersionHash, sourceText.ToString(), options, allowStaleResults = true)  |> Async.RunSynchronously
+
+            let declarations = 
+                checkFileResults.GetDeclarationLocationAlternate 
+                    (fcsTextLineNumber, lexerSymbol.Ident.idRange.EndColumn, textLine.ToString(), lexerSymbol.FullIsland, false) |> Async.RunSynchronously
+            
+            match declarations with
+            | FSharpFindDeclResult.DeclFound range -> return range
+            | _ -> return! None
+        }
+
     [<Test>]
     let VerifyDefinition() =
 
@@ -100,16 +121,12 @@ let _ = Module1.foo 1
         let caretPosition = fileContents.IndexOf(caretMarker) + caretMarker.Length - 1 // inside the marker
         let documentId = DocumentId.CreateNewId(ProjectId.CreateNewId())
         let actual = 
-           FSharpGoToDefinitionService.FindDefinition(FSharpChecker.Instance, documentId, SourceText.From(fileContents), filePath, caretPosition, [], options, 0) 
+           findDefinition(FSharpChecker.Instance, documentId, SourceText.From(fileContents), filePath, caretPosition, [], options, 0) 
            |> Option.map (fun range -> (range.StartLine, range.EndLine, range.StartColumn, range.EndColumn))
 
         if actual <> expected then 
             Assert.Fail(sprintf "Incorrect information returned for fileContents=<<<%s>>>, caretMarker=<<<%s>>>, expected =<<<%A>>>, actual = <<<%A>>>" fileContents caretMarker expected actual)
 
-
-
-
-
 #if EXE
     VerifyDefinition()
-#endif
+#endif
\ No newline at end of file