Structural setup around now forbidden undefined and null values (since v8) about node-lru-cache

[holgerd77]

👍

Thanks a lot for going so deep with your answer, yes, we already had this wrapping solution in parts, but since I thought about this whole thing a couple of rounds already I finally wanted to loot out a bit if this all things are structurally intended/necessary/whatever. 🙂

Generally, the whole upgrade to the TypeScript/non-default-export/whateer new versions (we upgraded from v7) worked pretty seamlessly.

[isaacs]

Yeah, rewriting in typescript exposed a conflict in how fetch() was possibly handling undefined values in the case of aborted fetches, unfortunately. It's a logical consequence of supporting ignoreFetchAbort and allowStaleOnFetchAbort, meaning that aborts aren't necessarily a failure, and I missed the implication when those features for added. I see this as ultimately my error, and typescript doing its job quite well, but still, annoying lol.

The clearest way to approach it imo is to have a special "no value here" value, like Symbol('undefined'), or wrap your values in an object like type Value = { value: MyThing | undefined }. It does add a step in the cache lookup, but it also means that cache.get(key) will either return undefined (not in cache) or {value:undefined} (known to be missing).