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fix(sdk): Do not always remove empty chunks from LinkedChunk #4216

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Merged
merged 1 commit into from
Nov 5, 2024
Merged

fix(sdk): Do not always remove empty chunks from LinkedChunk #4216

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17 changes: 13 additions & 4 deletions crates/matrix-sdk/src/event_cache/linked_chunk/as_vector.rs
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -452,7 +452,10 @@ mod tests {

use imbl::{vector, Vector};

use super::{super::LinkedChunk, VectorDiff};
use super::{
super::{EmptyChunk, LinkedChunk},
VectorDiff,
};

fn apply_and_assert_eq<Item>(
accumulator: &mut Vector<Item>,
Expand Down Expand Up @@ -614,7 +617,10 @@ mod tests {
);

let removed_item = linked_chunk
.remove_item_at(linked_chunk.item_position(|item| *item == 'c').unwrap())
.remove_item_at(
linked_chunk.item_position(|item| *item == 'c').unwrap(),
EmptyChunk::Remove,
)
.unwrap();
assert_eq!(removed_item, 'c');
assert_items_eq!(
Expand All @@ -634,7 +640,10 @@ mod tests {
apply_and_assert_eq(&mut accumulator, as_vector.take(), &[VectorDiff::Remove { index: 7 }]);

let removed_item = linked_chunk
.remove_item_at(linked_chunk.item_position(|item| *item == 'z').unwrap())
.remove_item_at(
linked_chunk.item_position(|item| *item == 'z').unwrap(),
EmptyChunk::Remove,
)
.unwrap();
assert_eq!(removed_item, 'z');
assert_items_eq!(
Expand Down Expand Up @@ -773,7 +782,7 @@ mod tests {
continue;
};

linked_chunk.remove_item_at(position).expect("Failed to remove an item");
linked_chunk.remove_item_at(position, EmptyChunk::Remove).expect("Failed to remove an item");
}
}
}
Expand Down
174 changes: 151 additions & 23 deletions crates/matrix-sdk/src/event_cache/linked_chunk/mod.rs
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -408,9 +408,18 @@ impl<const CAP: usize, Item, Gap> LinkedChunk<CAP, Item, Gap> {

/// Remove item at a specified position in the [`LinkedChunk`].
///
/// Because the `position` can be invalid, this method returns a
/// `Result`.
pub fn remove_item_at(&mut self, position: Position) -> Result<Item, Error> {
/// `position` must point to a valid item, otherwise the method returns
/// `Err`.
///
/// The chunk containing the item represented by `position` may be empty
/// once the item has been removed. In this case, the chunk can be removed
/// if `empty_chunk` contains [`EmptyChunk::Remove`], otherwise the chunk is
/// kept if `empty_chunk` contains [`EmptyChunk::Keep`].
pub fn remove_item_at(
&mut self,
position: Position,
empty_chunk: EmptyChunk,
) -> Result<Item, Error> {
let chunk_identifier = position.chunk_identifier();
let item_index = position.index();

Expand Down Expand Up @@ -446,9 +455,9 @@ impl<const CAP: usize, Item, Gap> LinkedChunk<CAP, Item, Gap> {
}
};

// If the `chunk` can be unlinked, and if the `chunk` is not the first one, we
// can remove it.
if can_unlink_chunk && chunk.is_first_chunk().not() {
// If removing empty chunk is desired, and if the `chunk` can be unlinked, and
// if the `chunk` is not the first one, we can remove it.
if empty_chunk.remove() && can_unlink_chunk && chunk.is_first_chunk().not() {
// Unlink `chunk`.
chunk.unlink(&mut self.updates);

Expand Down Expand Up @@ -1336,15 +1345,30 @@ where
}
}

/// A type representing what to do when the system has to handle an empty chunk.
pub(crate) enum EmptyChunk {
/// Keep the empty chunk.
Keep,

/// Remove the empty chunk.
Remove,
}

impl EmptyChunk {
fn remove(&self) -> bool {
matches!(self, Self::Remove)
}
}

#[cfg(test)]
mod tests {
use std::ops::Not;

use assert_matches::assert_matches;

use super::{
Chunk, ChunkContent, ChunkIdentifier, ChunkIdentifierGenerator, Error, LinkedChunk,
Position,
Chunk, ChunkContent, ChunkIdentifier, ChunkIdentifierGenerator, EmptyChunk, Error,
LinkedChunk, Position,
};

#[test]
Expand Down Expand Up @@ -1950,21 +1974,21 @@ mod tests {
// that. The chunk is removed.
{
let position_of_f = linked_chunk.item_position(|item| *item == 'f').unwrap();
let removed_item = linked_chunk.remove_item_at(position_of_f)?;
let removed_item = linked_chunk.remove_item_at(position_of_f, EmptyChunk::Remove)?;

assert_eq!(removed_item, 'f');
assert_items_eq!(linked_chunk, ['a', 'b', 'c'] ['d', 'e'] ['g', 'h', 'i'] ['j', 'k']);
assert_eq!(linked_chunk.len(), 10);

let position_of_e = linked_chunk.item_position(|item| *item == 'e').unwrap();
let removed_item = linked_chunk.remove_item_at(position_of_e)?;
let removed_item = linked_chunk.remove_item_at(position_of_e, EmptyChunk::Remove)?;

assert_eq!(removed_item, 'e');
assert_items_eq!(linked_chunk, ['a', 'b', 'c'] ['d'] ['g', 'h', 'i'] ['j', 'k']);
assert_eq!(linked_chunk.len(), 9);

let position_of_d = linked_chunk.item_position(|item| *item == 'd').unwrap();
let removed_item = linked_chunk.remove_item_at(position_of_d)?;
let removed_item = linked_chunk.remove_item_at(position_of_d, EmptyChunk::Remove)?;

assert_eq!(removed_item, 'd');
assert_items_eq!(linked_chunk, ['a', 'b', 'c'] ['g', 'h', 'i'] ['j', 'k']);
Expand All @@ -1985,19 +2009,19 @@ mod tests {
// that. The chunk is NOT removed because it's the first chunk.
{
let first_position = linked_chunk.item_position(|item| *item == 'a').unwrap();
let removed_item = linked_chunk.remove_item_at(first_position)?;
let removed_item = linked_chunk.remove_item_at(first_position, EmptyChunk::Remove)?;

assert_eq!(removed_item, 'a');
assert_items_eq!(linked_chunk, ['b', 'c'] ['g', 'h', 'i'] ['j', 'k']);
assert_eq!(linked_chunk.len(), 7);

let removed_item = linked_chunk.remove_item_at(first_position)?;
let removed_item = linked_chunk.remove_item_at(first_position, EmptyChunk::Remove)?;

assert_eq!(removed_item, 'b');
assert_items_eq!(linked_chunk, ['c'] ['g', 'h', 'i'] ['j', 'k']);
assert_eq!(linked_chunk.len(), 6);

let removed_item = linked_chunk.remove_item_at(first_position)?;
let removed_item = linked_chunk.remove_item_at(first_position, EmptyChunk::Remove)?;

assert_eq!(removed_item, 'c');
assert_items_eq!(linked_chunk, [] ['g', 'h', 'i'] ['j', 'k']);
Expand All @@ -2017,19 +2041,19 @@ mod tests {
// that. The chunk is removed.
{
let first_position = linked_chunk.item_position(|item| *item == 'g').unwrap();
let removed_item = linked_chunk.remove_item_at(first_position)?;
let removed_item = linked_chunk.remove_item_at(first_position, EmptyChunk::Remove)?;

assert_eq!(removed_item, 'g');
assert_items_eq!(linked_chunk, [] ['h', 'i'] ['j', 'k']);
assert_eq!(linked_chunk.len(), 4);

let removed_item = linked_chunk.remove_item_at(first_position)?;
let removed_item = linked_chunk.remove_item_at(first_position, EmptyChunk::Remove)?;

assert_eq!(removed_item, 'h');
assert_items_eq!(linked_chunk, [] ['i'] ['j', 'k']);
assert_eq!(linked_chunk.len(), 3);

let removed_item = linked_chunk.remove_item_at(first_position)?;
let removed_item = linked_chunk.remove_item_at(first_position, EmptyChunk::Remove)?;

assert_eq!(removed_item, 'i');
assert_items_eq!(linked_chunk, [] ['j', 'k']);
Expand All @@ -2050,15 +2074,15 @@ mod tests {
// The chunk is removed.
{
let position_of_k = linked_chunk.item_position(|item| *item == 'k').unwrap();
let removed_item = linked_chunk.remove_item_at(position_of_k)?;
let removed_item = linked_chunk.remove_item_at(position_of_k, EmptyChunk::Remove)?;

assert_eq!(removed_item, 'k');
#[rustfmt::skip]
assert_items_eq!(linked_chunk, [] ['j']);
assert_eq!(linked_chunk.len(), 1);

let position_of_j = linked_chunk.item_position(|item| *item == 'j').unwrap();
let removed_item = linked_chunk.remove_item_at(position_of_j)?;
let removed_item = linked_chunk.remove_item_at(position_of_j, EmptyChunk::Remove)?;

assert_eq!(removed_item, 'j');
assert_items_eq!(linked_chunk, []);
Expand Down Expand Up @@ -2092,27 +2116,27 @@ mod tests {
let _ = linked_chunk.updates().unwrap().take();

let position_of_c = linked_chunk.item_position(|item| *item == 'c').unwrap();
let removed_item = linked_chunk.remove_item_at(position_of_c)?;
let removed_item = linked_chunk.remove_item_at(position_of_c, EmptyChunk::Remove)?;

assert_eq!(removed_item, 'c');
assert_items_eq!(linked_chunk, ['a', 'b'] [-] ['d']);
assert_eq!(linked_chunk.len(), 3);

let position_of_d = linked_chunk.item_position(|item| *item == 'd').unwrap();
let removed_item = linked_chunk.remove_item_at(position_of_d)?;
let removed_item = linked_chunk.remove_item_at(position_of_d, EmptyChunk::Remove)?;

assert_eq!(removed_item, 'd');
assert_items_eq!(linked_chunk, ['a', 'b'] [-]);
assert_eq!(linked_chunk.len(), 2);

let first_position = linked_chunk.item_position(|item| *item == 'a').unwrap();
let removed_item = linked_chunk.remove_item_at(first_position)?;
let removed_item = linked_chunk.remove_item_at(first_position, EmptyChunk::Remove)?;

assert_eq!(removed_item, 'a');
assert_items_eq!(linked_chunk, ['b'] [-]);
assert_eq!(linked_chunk.len(), 1);

let removed_item = linked_chunk.remove_item_at(first_position)?;
let removed_item = linked_chunk.remove_item_at(first_position, EmptyChunk::Remove)?;

assert_eq!(removed_item, 'b');
assert_items_eq!(linked_chunk, [] [-]);
Expand All @@ -2134,6 +2158,110 @@ mod tests {
Ok(())
}

#[test]
fn test_remove_item_at_and_keep_empty_chunks() -> Result<(), Error> {
use super::Update::*;

let mut linked_chunk = LinkedChunk::<3, char, ()>::new_with_update_history();
linked_chunk.push_items_back(['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h']);
assert_items_eq!(linked_chunk, ['a', 'b', 'c'] ['d', 'e', 'f'] ['g', 'h']);
assert_eq!(linked_chunk.len(), 8);

// Ignore previous updates.
let _ = linked_chunk.updates().unwrap().take();

// Remove all items from the same chunk. The chunk is empty after that. The
// chunk is NOT removed because we asked to keep it.
{
let position = linked_chunk.item_position(|item| *item == 'd').unwrap();
let removed_item = linked_chunk.remove_item_at(position, EmptyChunk::Keep)?;

assert_eq!(removed_item, 'd');
assert_items_eq!(linked_chunk, ['a', 'b', 'c'] ['e', 'f'] ['g', 'h']);
assert_eq!(linked_chunk.len(), 7);

let removed_item = linked_chunk.remove_item_at(position, EmptyChunk::Keep)?;

assert_eq!(removed_item, 'e');
assert_items_eq!(linked_chunk, ['a', 'b', 'c'] ['f'] ['g', 'h']);
assert_eq!(linked_chunk.len(), 6);

let removed_item = linked_chunk.remove_item_at(position, EmptyChunk::Keep)?;

assert_eq!(removed_item, 'f');
assert_items_eq!(linked_chunk, ['a', 'b', 'c'] [] ['g', 'h']);
assert_eq!(linked_chunk.len(), 5);

assert_eq!(
linked_chunk.updates().unwrap().take(),
&[
RemoveItem { at: Position(ChunkIdentifier(1), 0) },
RemoveItem { at: Position(ChunkIdentifier(1), 0) },
RemoveItem { at: Position(ChunkIdentifier(1), 0) },
]
);
}

// Remove all items from the same chunk. The chunk is empty after that. The
// chunk is NOT removed because we asked to keep it.
{
let position = linked_chunk.item_position(|item| *item == 'g').unwrap();
let removed_item = linked_chunk.remove_item_at(position, EmptyChunk::Keep)?;

assert_eq!(removed_item, 'g');
assert_items_eq!(linked_chunk, ['a', 'b', 'c'] [] ['h']);
assert_eq!(linked_chunk.len(), 4);

let removed_item = linked_chunk.remove_item_at(position, EmptyChunk::Keep)?;

assert_eq!(removed_item, 'h');
assert_items_eq!(linked_chunk, ['a', 'b', 'c'] [] []);
assert_eq!(linked_chunk.len(), 3);

assert_eq!(
linked_chunk.updates().unwrap().take(),
&[
RemoveItem { at: Position(ChunkIdentifier(2), 0) },
RemoveItem { at: Position(ChunkIdentifier(2), 0) },
]
);
}

// Remove all items from the same chunk. The chunk is empty after that. The
// chunk is NOT removed because we asked to keep it.
{
let position = linked_chunk.item_position(|item| *item == 'a').unwrap();
let removed_item = linked_chunk.remove_item_at(position, EmptyChunk::Keep)?;

assert_eq!(removed_item, 'a');
assert_items_eq!(linked_chunk, ['b', 'c'] [] []);
assert_eq!(linked_chunk.len(), 2);

let removed_item = linked_chunk.remove_item_at(position, EmptyChunk::Keep)?;

assert_eq!(removed_item, 'b');
assert_items_eq!(linked_chunk, ['c'] [] []);
assert_eq!(linked_chunk.len(), 1);

let removed_item = linked_chunk.remove_item_at(position, EmptyChunk::Keep)?;

assert_eq!(removed_item, 'c');
assert_items_eq!(linked_chunk, [] [] []);
assert_eq!(linked_chunk.len(), 0);

assert_eq!(
linked_chunk.updates().unwrap().take(),
&[
RemoveItem { at: Position(ChunkIdentifier(0), 0) },
RemoveItem { at: Position(ChunkIdentifier(0), 0) },
RemoveItem { at: Position(ChunkIdentifier(0), 0) },
]
);
}

Ok(())
}

#[test]
fn test_insert_gap_at() -> Result<(), Error> {
use super::Update::*;
Expand Down
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