Merge pull request #9894 from huguesv/emptylinenooption

Allow interactive window evaluation of empty line.

src/InteractiveWindow/Editor/InteractiveWindow.UIThreadOnly.cs

@@ -845,16 +845,11 @@ private async Task SubmitAsync()
 
                     var snapshotSpan = CurrentLanguageBuffer.CurrentSnapshot.GetExtent();
                     var trimmedSpan = snapshotSpan.TrimEnd();
-
-                    if (trimmedSpan.Length == 0)
-                    {
-                        // TODO: reuse the current language buffer
-                        PrepareForInput();
-                        return;
-                    }
-                    else
+                    if (trimmedSpan.Length > 0)
                     {
                         _history.Add(historySpan);
+                    }
+
                     State = State.ExecutingInput;
 
                     StartCursorTimer();
@@ -876,7 +871,6 @@ private async Task SubmitAsync()
                         FinishExecute(executionResult.IsSuccessful);
                     }
                 }
-                }
                 catch (Exception e) when (_window.ReportAndPropagateException(e))
                 {
                     throw ExceptionUtilities.Unreachable;

src/InteractiveWindow/EditorTest/InteractiveWindowHistoryTests.cs

@@ -76,6 +76,29 @@ public async Task CheckHistoryPrevious()
             AssertCurrentSubmission(inputString);
         }
 
+        [WpfFact]
+        public async Task CheckHistoryPreviousWithAnEmptySubmission() {
+            //submit, submit, submit, up, up, up
+            const string inputString1 = "1 ";
+            const string inputString2 = " ";
+            const string inputString3 = "3 ";
+
+            await InsertAndExecuteInput(inputString1).ConfigureAwait(true);
+            await InsertAndExecuteInput(inputString2).ConfigureAwait(true);
+            await InsertAndExecuteInput(inputString3).ConfigureAwait(true);
+
+            _operations.HistoryPrevious();
+            AssertCurrentSubmission(inputString3);
+
+            //second input was empty, so it wasn't added to history
+            _operations.HistoryPrevious();
+            AssertCurrentSubmission(inputString1);
+
+            //has reached the top, no change
+            _operations.HistoryPrevious();
+            AssertCurrentSubmission(inputString1);
+        }
+
         [WpfFact]
         public async Task CheckHistoryPreviousNotCircular()
         {

src/InteractiveWindow/EditorTest/InteractiveWindowTests.cs

@@ -1089,6 +1089,13 @@ public async Task SubmitAsyncMultiple()
             await SubmitAsync("1", "2", "1 + 2").ConfigureAwait(true);
         }
 
+        [WorkItem(8569, "https://github.com/dotnet/roslyn/issues/8569")]
+        [WpfFact]
+        public async Task SubmitAsyncEmptyLine()
+        {
+            await SubmitAsync("1", "", "1 + 2").ConfigureAwait(true);
+        }
+
         private async Task SubmitAsync(params string[] submissions)
         {
             var actualSubmissions = new List<string>();