Add test and fix signature off-by-one (#782)

src/FsAutoComplete.Core/ParseAndCheckResults.fs

@@ -213,7 +213,7 @@ type ParseAndCheckResults
   }
 
   member __.TryGetToolTip (pos: Pos) (lineStr: LineStr) =
-    match Lexer.findLongIdents(pos.Column - 1, lineStr) with
+    match Lexer.findLongIdents(pos.Column, lineStr) with
     | None -> ResultOrString.Error "Cannot find ident for tooltip"
     | Some(col,identIsland) ->
       let identIsland = Array.toList identIsland

test/FsAutoComplete.Tests.Lsp/ExtensionsTests.fs

@@ -375,3 +375,57 @@ let analyzerTests state =
         do! server.Shutdown()
       })
     ]
+
+let signatureTests state =
+  let server =
+    async {
+      let path = Path.Combine(__SOURCE_DIRECTORY__, "TestCases", "Signature")
+      let scriptPath = Path.Combine(path, "Script.fsx")
+      let! (server, events) = serverInitialize path defaultConfigDto state
+      do! waitForWorkspaceFinishedParsing events
+      do! server.TextDocumentDidOpen { TextDocument = loadDocument scriptPath }
+      match! waitForParseResultsForFile "Script.fsx" events with
+      | Ok () ->
+        () // all good, no parsing/checking errors
+      | Core.Result.Error errors ->
+        failtestf "Errors while parsing script %s: %A" scriptPath errors
+
+      return server, scriptPath
+    }
+    |> Async.Cache
+
+  let verifySignature line (characterStart, characterEnd) expectedSignature =
+    let verifyAt character = async {
+      let! server, scriptPath = server
+      let pos: TextDocumentPositionParams = {
+        TextDocument =  { Uri = Path.FilePathToUri scriptPath }
+        Position = { Line = line; Character = character }
+      }
+      match! server.FSharpSignature pos with
+      | Ok { Content = content } ->
+        let r = JsonSerializer.readJson<CommandResponse.ResponseMsg<string>>(content)
+        Expect.equal r.Kind "typesig" "Should have a kind of 'typesig'"
+        Expect.equal r.Data expectedSignature (sprintf "Should have a signature of '%s' at character %d" expectedSignature character)
+      | Result.Error errors ->
+        failtestf "Error while getting signature: %A" errors
+    }
+
+    testCaseAsync (sprintf "fsharp/signature for line %d characters [%d, %d] should be '%s'" line characterStart characterEnd expectedSignature) (
+      [ for c in characterStart .. characterEnd -> verifyAt c ]
+      |> Async.Sequential
+      |> Async.map (fun _ -> ())
+    )
+
+  testSequenced <|
+    testList "signature evaluation" [
+      testList "tests" [
+        verifySignature 0 (4, 16) "val arrayOfTuples : (int * int) []"
+        verifySignature 1 (4, 15) "val listOfTuples : (int * int) list"
+        verifySignature 2 (4, 15) "val someFunction : a:'a -> unit"
+      ]
+      testCaseAsync "cleanup" (async {
+        let! server, _ = server
+        do! server.Shutdown()
+      })
+  ]
+

test/FsAutoComplete.Tests.Lsp/Program.fs

@@ -59,6 +59,7 @@ let tests =
         // fake isn't updated to FCS 39, disabling tests until that's resolved
         //fakeInteropTests toolsPath
         analyzerTests state
+        signatureTests state
         SignatureHelp.tests state
         CodeFixTests.tests state
         Completion.tests state

test/FsAutoComplete.Tests.Lsp/TestCases/Signature/Script.fsx

@@ -0,0 +1,3 @@
+let arrayOfTuples = [| 1, 2 |]
+let listOfTuples = [ 1, 2 ]
+let someFunction a = ()