Introduce caching for strict templates

[vrugtehagel]

Currently, in Vento strict mode, templates are re-evaluated every time they are run, because the variables passed to the template can change.

This introduces a "strict cache", i.e. cache for strict mode, which caches templates separately based on the variables passed to them. This improves rendering performance significantly, since most of the time, the templates receive the same set of variables. On my laptop I'm seeing an improvement to the rendering benchmark of more than 50%!

Note that this respects Vento's env.cache.clear() because the variable-based caches are attached to the template objects, which are deleted upon clearing with env.cache.clear().

[oscarotero]

This is a smart solution, thank you!
Can you add tests for this? Maybe just checking the cache keys after calling the same template multiple times with different variables.

[vrugtehagel]

Of course! I added a test that checks the keys in strictCache, which doesn't completely prove that it works, but is at least an indication. It's a bit difficult to test it thoroughly without having to make adjustments to the implementation just for testing purposes, but I think this test should do well enough, and really, it doesn't really matter what it does, as long as the benchmarks are good and the rest of the tests pass.

By the way, I found using a Map instead of a plain object to be significantly slower somehow. Maybe just because it's a more expensive data structure, but I thought this was interesting 😄

[oscarotero]

Thank you!.

I found using a Map instead of a plain object to be significantly slower somehow.

That's interesting. I suspect Map and Set are faster with big volume or data, but if the object or array has only a few items, maybe it doesn't worth it. At least that's my experience using them. I also use them for inmutable data: data that is defined once and then you only check if it's there, without adding or removing elements. For example here.