Editing some large files in the Zig compiler is very slow

[alexrp]

Per the title, doing any kind of editing on large source files in the Zig compiler is very slow. On these files, every keystroke takes anywhere from half a second to several seconds to be fully processed.

src/codegen/x86_64/CodeGen.zig is the worst offender, but src/Sema.zig is also quite bad.

This happens even with LSP disabled, so it doesn't appear to be an issue in ZLS.

[neurocyte]

Have you tried disabling syntax highlighting? I suspect this could be a tree-sitter edge case.

[alexrp]

That seems to be it; without syntax highlighting, it's back to being snappy as usual.

[neurocyte]

Ok, the issue is that flow reverts to a full tree-sitter parse if the usual incremental parse produces parse errors for any reason. For large files full reparsing on every keystroke is too slow. I'll add some sort of large file threshold where we keep incremental parsing, even with errors, and just accept the occasional bad syntax highlighing.

[quangdn42]

FYI Snacks.nvim's bigfile module allows the user to set a threshold in MiB or count of lines, and when the threshold is met a message is shown to the user and tree-sitter is just disabled. This feels like the best for UX and complexity. I found that a consistent experience without tree-sitter is better than some broken highlighting, but that is subjective of course.