feat: add return val to replace_bucket_with replace_entry_with
#419
Conversation
If a user has a `RawOccupiedEntryMut`, they should be able to use `replace_entry_with` to conditionally remove it. However, if a user wishes to extract data from this entity during the removal process, the current api necessitates the use of `unwrap`:
```rust
/// Extract the coolness of an item, possibly destroying it
fn extract_coolness<V>(v: V) -> (Option<V>, Coolness) {
/// ...
}
let entry: RawOccupiedEntryMut< _, _, _, _> = unimplemented!();
let mut coolness = None;
let entry = entry.replace_entry_with(|_k, v| {
let (maybe_v, rcool) = extract_coolness(v);
coolness = Some(rcool);
maybe_v
});
let coolness = coolness.unwrap(); // unwrap, ew
// Do some stuff with the coolness it doesn't really matter what
inspect_coolness(coolness);
```
This is because while `F` is bounded by `FnOnce`, it is under no obligation to call it, which in this example means there is no guarnatee that `coolness` is initialized. This proposed change introduces a new return value `R` which allows callers to transport this data out of `F`. Notably it also commits the `replace_entry_with` to calling `F`, since there is no other way to generate an `R`. With this, our example becomes:
```rust
/// Extract the coolness of an item, possibly destroying it
fn extract_coolness<V>(v: V) -> (Option<V>, Coolness) {
/// ...
}
let entry: RawOccupiedEntryMut< _, _, _, _> = unimplemented!();
let (entry, coolness) = entry.replace_entry_with(|_k, v| extract_coolness(v));
// Do some stuff with the coolness it doesn't really matter what
inspect_coolness(coolness);
```
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Is there any interest in this change? |
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☔ The latest upstream changes (presumably #425) made this pull request unmergeable. Please resolve the merge conflicts. |
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I spent some time thinking about this change. I don't think it is beneficial because it makes the common case where you don't want to return a value more complicated since you need to extract the new |
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It is only a |
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Long-term, I am planning on deprecating the whole RawEntry API and replacing it with a |
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I would like to deprecate the raw entry API in favor of |
If a user has a
RawOccupiedEntryMut, they should be able to usereplace_entry_withto conditionally remove it. However, if a user wishes to extract data from this entity during the removal process, the current api necessitates the use ofunwrap:This is because while
Fis bounded byFnOnce, it is under no obligation to call it, which in this example means there is no guarnatee thatcoolnessis initialized. This proposed change introduces a new return valueRwhich allows callers to transport this data out ofF. Notably it also commits thereplace_entry_withto callingF, since there is no other way to generate anR. With this, our example becomes:An alternative to this change is to introduce a new API with a new name instead of modifying the existing one as this is a breaking change.