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Fix virtual insertion indexing for single-item buffers #91

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Merged
dhilt merged 1 commit into from
Oct 23, 2026
Merged

Fix virtual insertion indexing for single-item buffers #91

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5 changes: 3 additions & 2 deletions src/classes/buffer.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -218,10 +218,11 @@ export class Buffer<Data> {
if (!this.checkCall.insertVirtual(items, index, direction)) {
return false;
}
const indexToInsert = index + (direction === Direction.forward ? 1 : 0);
let shift = 0;
if (index <= this.firstIndex && !fixRight) {
if (indexToInsert <= this.firstIndex && !fixRight) {
shift = items.length;
} else if (index >= this.lastIndex && fixRight) {
} else if (indexToInsert > this.lastIndex && fixRight) {
shift = -items.length;
}
if (shift) {
Expand Down
90 changes: 72 additions & 18 deletions tests/e2e/specs/adapter.append-prepend.spec.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -111,15 +111,15 @@ const addItems = (
) =>
operation === Adapter.append
? misc.adapter.append({
items,
decrease: opposite,
...(virtualize ? { virtualize: true } : { eof: !!boundary })
})
items,
decrease: opposite,
...(virtualize ? { virtualize: true } : { eof: !!boundary })
})
: misc.adapter.prepend({
items,
increase: opposite,
...(virtualize ? { virtualize: true } : { bof: !!boundary })
});
items,
increase: opposite,
...(virtualize ? { virtualize: true } : { bof: !!boundary })
});

const createBasicConfig = (operation: Operation): TestConfig => ({
datasource: () => getDatasource({ min, max }),
Expand Down Expand Up @@ -155,23 +155,36 @@ const createVirtualConfig = (
templateSettings: { viewportHeight: 200, itemHeight: itemSize }
});

const createSingleItemConfig = (): TestConfig => ({
datasource: () => new MutableDatasource(min, min),
datasourceSettings: {
startIndex: min,
minIndex: min,
maxIndex: min,
itemSize,
bufferSize: 1,
padding
},
templateSettings: { viewportHeight: itemSize, itemHeight: itemSize }
});

const createEmptyConfig = (
operation: Operation,
indexed: boolean
): TestConfig => ({
datasource: () => getDatasource({ min: 1, max: 0 }),
datasourceSettings: indexed
? {
startIndex:
operation === Adapter.append
? max - emptyAmount + 1
: min + emptyAmount - 1,
...(operation === Adapter.append
? { maxIndex: max - emptyAmount + 1 }
: { minIndex: min + emptyAmount - 1 }),
bufferSize: emptyAmount,
padding
}
startIndex:
operation === Adapter.append
? max - emptyAmount + 1
: min + emptyAmount - 1,
...(operation === Adapter.append
? { maxIndex: max - emptyAmount + 1 }
: { minIndex: min + emptyAmount - 1 }),
bufferSize: emptyAmount,
padding
}
: {},
templateSettings: { viewportHeight: 200, itemHeight: itemSize }
});
Expand Down Expand Up @@ -300,6 +313,46 @@ const registerVirtual = (
}
});

const registerSingleItem = (operation: Operation, opposite: boolean): void =>
makeTest({
config: createSingleItemConfig(),
title:
`should ${operation} virtually next to a single buffered item` +
(opposite ? ' (opposite)' : ''),
it: misc => async () => {
await misc.relaxNext();
const append = operation === Adapter.append;
const fixRight = append ? opposite : !opposite;
const shift = opposite ? (append ? -amount : amount) : 0;
const { buffer } = misc.scroller;
const [item] = buffer.items;
const items = makeItems(append ? min + 1 : min - amount, amount);

expect(buffer.size).toBe(1);

misc.source<MutableDatasource>().insert(items, min, !append, fixRight);
const result = await addItems(misc, operation, items, opposite, false, true);
expect(result.success).toBe(true);

expect(item.$index).toBe(min + shift);
expect(buffer.items.find(({ data }) => data.id === min)).toBe(item);
expect(buffer.absMinIndex).toBe(min - (fixRight ? amount : 0));
expect(buffer.absMaxIndex).toBe(min + (fixRight ? 0 : amount));
misc.expect.domIndexesMatchBuffer();
expect(misc.checkElementContent(item.$index, min)).toBe(true);

if (append) {
await misc.scrollMaxRelax();
} else {
await misc.scrollMinRelax();
}
const edgeIndex = append ? buffer.absMaxIndex : buffer.absMinIndex;
const edgeId = append ? min + amount : min - amount;
expect(misc.checkElementContent(edgeIndex, edgeId)).toBe(true);
misc.expect.domIndexesMatchBuffer();
}
});

const registerEmpty = (
operation: Operation,
opposite: boolean,
Expand Down Expand Up @@ -358,6 +411,7 @@ describe('Adapter Append-Prepend Spec', () =>
[false, true].forEach(boundary =>
registerEmpty(operation, opposite, true, boundary)
);
registerSingleItem(operation, opposite);
registerEmpty(operation, opposite, false);
})
));
118 changes: 92 additions & 26 deletions tests/unit/buffer.spec.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -43,29 +43,29 @@ const makeBuffer = (params: BufferParams): Buffer<Data> => {

const checkUpdate =
({ min, max, predicate, fixRight, list }: BufferUpdateConfig) =>
() => {
const buffer = makeBuffer({ min, max });
buffer.updateItems(predicate, cb, NaN, fixRight);
// console.log(buffer.items.map(i => i.get()));
expect(buffer.size).toEqual(list.length);
list.forEach((current, index) => {
const $index = Number(Object.keys(current)[0]);
if (index === 0) {
expect(buffer.firstIndex).toEqual($index);
expect(buffer.minIndex).toEqual($index);
expect(buffer.absMinIndex).toEqual($index);
}
if (index === list.length - 1) {
expect(buffer.lastIndex).toEqual($index);
expect(buffer.maxIndex).toEqual($index);
expect(buffer.absMaxIndex).toEqual($index);
}
const id = current[$index];
const item = buffer.items[index];
expect(item.$index).toEqual($index);
expect(item.data.id).toEqual(id);
});
};
() => {
const buffer = makeBuffer({ min, max });
buffer.updateItems(predicate, cb, NaN, fixRight);
// console.log(buffer.items.map(i => i.get()));
expect(buffer.size).toEqual(list.length);
list.forEach((current, index) => {
const $index = Number(Object.keys(current)[0]);
if (index === 0) {
expect(buffer.firstIndex).toEqual($index);
expect(buffer.minIndex).toEqual($index);
expect(buffer.absMinIndex).toEqual($index);
}
if (index === list.length - 1) {
expect(buffer.lastIndex).toEqual($index);
expect(buffer.maxIndex).toEqual($index);
expect(buffer.absMaxIndex).toEqual($index);
}
const id = current[$index];
const item = buffer.items[index];
expect(item.$index).toEqual($index);
expect(item.data.id).toEqual(id);
});
};

const checkIndexTrackingOnUpdate = (params: BufferUpdateTrackConfig) => () => {
const { index, predicate, fixRight, result, debug = false } = params;
Expand Down Expand Up @@ -99,22 +99,32 @@ tracked index: ${trackedIndex ? `${trackedIndex}~${trackedItem ? trackedItem.get
const checkInsert = (params: BufferInsertConfig) => () => {
const bufferBefore = makeBuffer(params);
const buffer = makeBuffer(params);
const beforeItems = [...buffer.items];
const { result } = params;
const items = params.items.map(id => generateItem(id));
buffer.insertVirtually(
const resultInsert = buffer.insertVirtually(
items,
params.index,
params.direction,
params.fixRight
);
expect(resultInsert).toBe(!!result);
expect(buffer.size).toBe(beforeItems.length);

buffer.items.forEach((item, i) => {
const $index = result
? Number(Object.keys(result.list[i])[0])
: bufferBefore.items[i].$index;
const id = result ? result.list[i][$index] : bufferBefore.items[i].data.id;
expect(item).toBe(beforeItems[i]);
expect(item.$index).toBe($index);
expect(item.data.id).toBe(id);
if (i === 0) {
expect(buffer.minIndex).toBe($index);
}
if (i === buffer.size - 1) {
expect(buffer.maxIndex).toBe($index);
}
});

expect(buffer.absMinIndex).toEqual(
Expand Down Expand Up @@ -152,7 +162,7 @@ describe('Buffer Spec', () => {
case 4:
return () => null;
case 5:
return class {};
return class { };
case 6:
return new Map();
case 7:
Expand Down Expand Up @@ -1160,9 +1170,65 @@ describe('Buffer Spec', () => {
index: -101,
direction: Direction.backward,
fixRight: true
},
{
title: 'before a single buffered item, backward',
items: ['A', 'B'],
index: 5,
direction: Direction.backward,
fixRight: false,
min: 5,
max: 5,
result: {
list: [{ 7: 5 }],
absMin: -100,
absMax: 102
}
},
{
title: 'before a single buffered item, backward + fixRight',
items: ['A', 'B'],
index: 5,
direction: Direction.backward,
fixRight: true,
min: 5,
max: 5,
result: {
list: [{ 5: 5 }],
absMin: -102,
absMax: 100
}
},
{
title: 'after a single buffered item, forward',
items: ['A', 'B'],
index: 5,
direction: Direction.forward,
fixRight: false,
min: 5,
max: 5,
result: {
list: [{ 5: 5 }],
absMin: -100,
absMax: 102
}
},
{
title: 'after a single buffered item, forward + fixRight',
items: ['A', 'B'],
index: 5,
direction: Direction.forward,
fixRight: true,
min: 5,
max: 5,
result: {
list: [{ 3: 5 }],
absMin: -102,
absMax: 100
}
}
]
.map(c => ({ ...c, min: -1, max: 1, absMin: -100, absMax: 100 }))
.map(c => ({ min: -1, max: 1, absMin: -100, absMax: 100, ...c }))
.forEach(config =>
it(config.title, checkInsert(config as BufferInsertConfig))
));
Expand Down
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