System.NullReferenceException on Undo

[workgroupengineering]

How to simulate:

• Clone latest master 88625c4
• Open AvaloniaEdit.sln
• Run AvaloniaEdit.Demo
• Go to line 62
• Press Enter key
• Click on Button Insert Snipet
• Edit name in aaa and press Enter key for confirm the change
• Press CTRL+Z four times
• The exception will be thrown

[Rekkonnect]

The action of adding a snippet adds multiple lines and thus exposes the lack of checking whether the invalidated line range is out of bounds. The call stack shows that the exception is ultimately thrown by TextMateSharp because it attempts to read the line at the given index, without checking whether it's in bounds. This can be retrieved via the GetNumberOfLines() method from the model, and evaluated such that InvalidateLineRange(int, int) doesn't run the loop with out of bounds indexes.

@danipen Does this belong to https://github.com/danipen/TextMateSharp? Then this issue would track the respective issue in that repo.

[danipen]

I'd say this should be fixed at this layer: https://github.com/AvaloniaUI/AvaloniaEdit/blob/master/src/AvaloniaEdit.TextMate/TextEditorModel.cs