Personally, I think the reason most "good" semantic diff tools are proprietary is that they are huge amounts of effort that are mostly "hacks" and "heuristics" bandaged together in ways that people don't want to let out how the sausage was made.
But I also think "general, language agnostic AST-based semantic diff" is a mountain peak we cannot reach (probably ever), and I believe my experiments found an interesting local maxima that people are maybe passing by on the way to that ideal mountain (lexer-based diffs rather than parser-based diffs): https://github.com/WorldMaker/tokdiff
I know a lot of people who have a lot of hope for diffsitter (or something like it): https://github.com/afnanenayet/diffsitter
Personally, I think the reason most "good" semantic diff tools are proprietary is that they are huge amounts of effort that are mostly "hacks" and "heuristics" bandaged together in ways that people don't want to let out how the sausage was made.
But I also think "general, language agnostic AST-based semantic diff" is a mountain peak we cannot reach (probably ever), and I believe my experiments found an interesting local maxima that people are maybe passing by on the way to that ideal mountain (lexer-based diffs rather than parser-based diffs): https://github.com/WorldMaker/tokdiff