Improve performance of hidden node parsing #1790
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I was hesitating with the approval, but actually there is no need for waiting, I got it. If you want an additional approval or more comments, you could reach out for Ben. Or ask me, what I should look at specifically.
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I've noticed in a project with a large file with a lot of comments (~20 000 LoC, ~10 000 comments), that parsing started taking a huge performance hit. It seems like our current method of iterating through the CST to add hidden nodes leads to super-linear behavior in the parsing phase.
You can reproduce this by using the test I've added to
langium-parser.test.tsand run it on the currentmainbranch. While the parse takes only ~150ms on my machine with the new changes, it takes roughly ~5000ms onmain.This change replaces the existing hidden node placement algorithm with a different one that should perform linearly. Note that the placement of the hidden nodes has not changed with this algorithm. Existing tests (and also a few new ones) verify this behavior.
Some ideas for this new algorithm were taken from #1733.