Modifying key without changing order

[beviu]

Hello, thank you for this very nice crate!

Is there a way to modify an entry's key without changing its position? I use this crate to implement a cache and sometimes the key associated with an object changes, so I would like to modify it without having to reinsert the entry as it would put it on the back.

In case there is no such API, would you accept a PR that adds it? If so, how do you think that API should look like?

I thought about adding a replace_key method on LinkedHashMap itself, or maybe adding a reinsert method on RawOccupiedEntryMut but the latter looks more complicated because the RawOccupiedEntryMut does not have a reference to the hashbrown HashMap and I think it cannot be added because the hashbrown raw entry borrows it. I don't really know how these methods should handle an entry with the new key already existing. In my case, I would like to cancel the operation.

[beviu]

I think it would make more sense for hashbrown to have an easy way to reinsert an entry after modifying its key first before adding it here. I have created a PR on hashbrown (rust-lang/hashbrown#450) to add a reinsert method on their RawOccupiedEntryMut that does this. Let's see what they think about it.

[qtfkwk]

I think I just ran into this... Ethiraric/yaml-rust2#35

Summary: I'd recommend replacing use of the entry / and_modify / or_insert_with pattern (which moves entries to the end) to the contains_key / replace / insert pattern. More info at the above link.

[olebedev]

After the cursor API PR #25 was merged it's possible now to insert elements into any location within the underlying doulby-linked list.

I hope that helps resolving addressing issue.

[beviu]

I'd recommend replacing use of the entry / and_modify / or_insert_with pattern (which moves entries to the end) to the contains_key / replace / insert pattern.

I think that replace doesn't fit my use case because I wanted to change the key and preserve the value whereas replace does the opposite: it changes the value and preserves the key.

After the cursor API PR #25 was merged it's possible now to insert elements into any location within the underlying doulby-linked list.

I hope that helps resolving addressing issue.

Yes, I think this PR allows doing this. To update a key you can now use CursorMut::insert_before with the new key and then LinkedHashMap::remove (or CursorMut::remove_current if somebody adds it) to remove the original entry.

Thanks for the responses!