Preserve blank MU* output lines in WorldSession

src/SharpMUTerm.Core/Session/WorldSession.cs

@@ -312,15 +312,22 @@ private void OnOutputReceived(object? sender, TelnetOutputEventArgs e)
             return;
         }
 
+        var emitted = false;
         foreach (var completed in _parser.Feed(e.Text))
         {
             ProcessOutputLine(completed);
+            emitted = true;
         }
 
         var tail = _parser.Flush();
         if (tail is not null)
         {
             ProcessOutputLine(tail);
+            emitted = true;
+        }
+        else if (!emitted)
+        {
+            ProcessOutputLine(StyledLine.Empty);
         }
     }
 

tests/SharpMUTerm.Core.Tests/Session/WorldSessionTests.cs

@@ -34,6 +34,36 @@ public async Task OutputLine_IsAppendedToScrollbackAndRaisesEvent()
         await Assert.That(printed).IsNotNull();
     }
 
+    [Test]
+    public async Task EmptyOutputLine_IsAppendedAsBlankLine()
+    {
+        var (session, telnet) = Create(World());
+        await session.ConnectAsync();
+        var before = session.Scrollback.Snapshot().Count;
+
+        telnet.EmitLine(string.Empty);
+
+        var after = session.Scrollback.Snapshot();
+        await Assert.That(after.Count).IsEqualTo(before + 1);
+        await Assert.That(after[^1].IsEmpty).IsTrue();
+    }
+
+    [Test]
+    public async Task SameFrame_OutputPreservesAnEmptyMiddleLine()
+    {
+        var (session, telnet) = Create(World());
+        await session.ConnectAsync();
+        var before = session.Scrollback.Snapshot().Count;
+
+        telnet.EmitLine("Line one\n\nThis line three, previous line was empty, this is valid output. It came from the same received frame.");
+
+        var after = session.Scrollback.Snapshot();
+        await Assert.That(after.Count).IsEqualTo(before + 3);
+        await Assert.That(after[before].Text).IsEqualTo("Line one");
+        await Assert.That(after[before + 1].IsEmpty).IsTrue();
+        await Assert.That(after[before + 2].Text).IsEqualTo("This line three, previous line was empty, this is valid output. It came from the same received frame.");
+    }
+
     [Test]
     public async Task AnsiColor_InOutput_IsParsedIntoStyledSpans()
     {