getTotalSize() returns 0 when using multiple lanes with a single item

[greenblues1190]

Describe the bug

Starting from version 3.13.3, the behavior of virtualizer.getTotalSize() has changed. When using multiple lanes (i.e., lanes > 1) and the item count is 1, getTotalSize() now returns 0.
This did not happen in 3.13.2, where the total size of a single item was calculated and returned correctly.

If this change in behavior is intentional, please let me know.

Your minimal, reproducible example

https://stackblitz.com/edit/tanstack-virtual-4zlr1xau

Steps to reproduce

1. start app npm install && npm run start
2. variable settings
   • @tanstack/react-virtual version: 3.13.2
   • lanes: 2
   • contents count: 1
3. change VERSION(main.tsx#L8) to "3.13.3" and observe that the same setup returns the expected item size.

Expected behavior

with count === 1 and lanes > 1, getTotalSize() should return the size of the single item, not 0.

How often does this bug happen?

Every time

Screenshots or Videos

2025-03-24.2.11.38.mov

Platform

• OS: macOS 13.3.1 22E261 arm64
• Browser: Chrome 134.0.6998.89 (arm64)

tanstack-virtual version

v3.13.3

TypeScript version

No response

Additional context

No response

Terms & Code of Conduct

• I agree to follow this project's Code of Conduct
• I understand that if my bug cannot be reliable reproduced in a debuggable environment, it will probably not be fixed and this issue may even be closed.

[soren121]

Sorry, that's my bug! Pretty obvious now that I see it. Thanks @Ryanromaris for fixing it :)

[greenblues1190]

The issue seems to still occur in 3.13.5 when there's only one item and multiple lanes. I've submitted a follow-up PR to address this: #967

Would appreciate a review when you get a chance!

reproduce: https://stackblitz.com/edit/tanstack-virtual-4zlr1xau?file=src%2Fmain.tsx

resolved