feat: Add ChangeSet that can be collected into from iterators, and joined over for easy application to components

[Rhuagh]

This change is 

[torkleyy]

Reviewed 8 of 8 files at r1, 1 of 1 files at r2.
Review status: all files reviewed at latest revision, all discussions resolved.

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Comments from Reviewable

[torkleyy]

Thank you!

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Review status: all files reviewed at latest revision, all discussions resolved, some commit checks pending.

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Comments from Reviewable

[Rhuagh]

Not 100% ready yet.

[Rhuagh]

Ready now I believe.

[torkleyy]

Reviewed 1 of 1 files at r3.
Review status: all files reviewed at latest revision, 3 unresolved discussions.

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src/changeset.rs, line 58 at r3 (raw file):

    pub fn add(&mut self, entity: Entity, value: T)
    where
        T: AddAssign + Default,

I don't think the Default is necessary.

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src/changeset.rs, line 73 at r3 (raw file):

}

impl<T> FromIterator<(Entity, T)> for ChangeSet<T>

An Extend implementation would also be useful

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src/changeset.rs, line 86 at r3 (raw file):

}

impl<'a, T> Join for &'a ChangeSet<T> {

I think we also need an implementation for ChangeSet and &mut ChangeSet.

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Comments from Reviewable

[torkleyy]

Review status: all files reviewed at latest revision, 4 unresolved discussions.

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src/changeset.rs, line 47 at r3 (raw file):

impl<T> ChangeSet<T> {
    /// Create a new change set
    pub fn new() -> Self {

One might want to keep the ChangeSet to save a allocations, so in addition to Extend a clear method would also be useful.

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Comments from Reviewable

[Rhuagh]

Review status: 7 of 8 files reviewed at latest revision, 4 unresolved discussions.

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src/changeset.rs, line 47 at r3 (raw file):

Previously, torkleyy (Thomas Schaller) wrote…

One might want to keep the ChangeSet to save a allocations, so in addition to Extend a clear method would also be useful.

Done.

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src/changeset.rs, line 58 at r3 (raw file):

Previously, torkleyy (Thomas Schaller) wrote…

I don't think the Default is necessary.

Done.

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src/changeset.rs, line 73 at r3 (raw file):

Previously, torkleyy (Thomas Schaller) wrote…

An Extend implementation would also be useful

Done.

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src/changeset.rs, line 86 at r3 (raw file):

Previously, torkleyy (Thomas Schaller) wrote…

I think we also need an implementation for ChangeSet and &mut ChangeSet.

Done.

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Comments from Reviewable

[torkleyy]

I don't think this is necessary.

[Rhuagh]

It is taken from the Join on &mut Storage, it's required for the compiler to understand that v is mutable.

[Rhuagh]

It fails to validate the lifetime without it.

[Rhuagh]

The basic issue is that it fails to match &mut on the function signature to &'a for the Join implementation, and it's not possible to set &'a on the function signature because it would not match the trait then.

[torkleyy]

Ah, right.

[torkleyy]

Reviewed 1 of 1 files at r4.
Review status: all files reviewed at latest revision, 3 unresolved discussions.

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src/changeset.rs, line 40 at r4 (raw file):

/// # }
/// ```
pub struct ChangeSet<T> {

This needs a Drop implementation clearing the DenseVecStorage.

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src/changeset.rs, line 76 at r4 (raw file):

        for id in &self.mask {
            unsafe {
                self.inner.remove(id);

Can use UnprotectedStorage::clean instead.

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Comments from Reviewable

[torkleyy]

Thank you!

bors r+

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Review status: all files reviewed at latest revision, all discussions resolved, all commit checks successful.

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Comments from Reviewable

[bors]

Build succeeded

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