Add buffer-local caching to friendly-session calculation #3463
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Friendly session calculation has always be at least a touch slow (ref, ref), and even more so following recent additions to it.
All slow paths have in common that they run
seq-find
over a series of sequences (the classpath, classpath roots, the ns list). Those can be arbitrarily large.We may do relatively expensive stuff for each element, like trying to match a string.
So, this PR adds buffer-local caching.
The buffer-local caching is essentially this map:
<repl buffer>
-><is this buffer considered friendly to it?>
There are timestamps to ensure that we're not basing the caching on stale data.
From a quick test, it appears to work. Anyway I'll keep this as a draft to give it at least a couple days of QAing. Review welcome!