Autotracking Memoization

[pzuraq]

Rendered

[BryanCrotaz]

Looks good. Solves my usages of observes, for example playing a video element on a data change.

[BryanCrotaz]

This should be a decorator?

[pzuraq]

@BryanCrotaz no, this is meant to be a low-level API only. Decorators like @cached will be based on it (I need to update the text of that RFC, have updated the name already), and it would also allow us to build things like the @use and Resources RFC in userland for the most part.

[richard-viney]

Couple minor typos in the first line of the usage section: cache => createCache(), and "an cache" => "a cache".

[rwjblue]

We discussed this in todays core team meeting, and are moving it into final comment period. Time to read through it again! 😸 👓 🤓

[snewcomer]

I really like this RFC and well written. Some of the low level primitives that have been exposed recently have been immensely useful. So along the same track, this seems like a great idea!

[rwjblue]

Let's remove the isCache API for now (if we have a use case that comes up later, we can definitely add it).

[wycats]

For historical reference:

I was momentarily worried that this RFC doesn't provide an easy way to check whether a computation is const without creating unnecessary garbage.

This problem isn't semantic: it's not a semantic problem to create a Cache and immediately throw it away. I was worried, at first, that this API would make it difficult to implement Glimmer's strategy of running a computation, checking if it was const, and only bothering to cache the value at all if the value wasn't const.

@pzuraq persuaded me that the current spec allows this implementation: the implementation could check to see if the computation is const and not bother to store the value at all if it is.

This whole thing only matters if the cost of storing the cache momentarily is a notable cost. If it turns out to be a serious issue, and @pzuraq's thinking turns out to be wrong, we could always revisit this issue.

[rwjblue]

FYI - @pzuraq created a polyfill for this that works back to ember-source@3.13 (going further back is very very difficult since autotracking in general is missing).

Check it out https://github.com/ember-polyfills/ember-cache-primitive-polyfill