rustyconover opened a new issue, #403:
URL: https://github.com/apache/arrow-js/issues/403
## Description
In `src/data.ts`, `visitStruct` computes a default `length` via:
```typescript
length = children.reduce((len, { length }) => Math.max(len, length), 0),
```
When `children` is `[]` and `props.length` is omitted, `reduce` returns `0`.
This silently discards any intended row count for zero-child Struct data.
## Impact
Two callers in `src/recordbatch.ts` omit `length` when calling `makeData`
for Struct types:
- **`setChildAt`** (line 264): `makeData({ type: new Struct<T>(fields),
children })` — should pass `length: data.length` to preserve the batch's row
count
- **`_InternalEmptyPlaceholderRecordBatch`** (line 383): `makeData({ type:
new Struct<T>(schema.fields), nullCount: 0, children })` — should pass `length:
0` explicitly
Both work today because they always have children to reduce over, but
they're fragile — any future change that results in empty children would
silently drop the row count.
## Proposed Fix
Pass explicit `length` in both `makeData` call sites so they don't rely on
the reduce-over-children fallback.
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