How do you cope with syntax errors ? e.g. saving garbage tex as source code ? And reversely, can you have visual informations that can't be pretty-printed as te

How do you cope with syntax errors ? e.g. saving garbage tex as source code ? And reversely, can you have visual informations that can't be pretty-printed as text easily? (e.g. nodes without names) How do you expect the visual syntax to integrate with VCSs? Do you have an algorithm and UI to present visual conflicts? How is the layout after a Git merge? Cheers