Tile corruption crash when repeatedly navigating to document start/end in @codemirror/view 6.39.x

[Fergarram]

Describe the issue

Repeatedly navigating between document start and end using Cmd+Up / Cmd+Down (or Ctrl+Home / Ctrl+End) causes a crash after approximately 3 round trips. The error originates in the tile rendering system.

Error messages:

Uncaught TypeError: Cannot destructure property 'tile' of 'parents.pop(...)' as it is undefined.
    at TilePointer.advance
    at TileUpdate.forward
    at TileUpdate.run

Followed by:

Uncaught Error: No tile at position 10316
    at DocTile.resolveBlock
    at DocView.coordsAt
    at DocView.scrollIntoView

This is not a timing issue, it reproduces even with several seconds between keystrokes.

The pattern is consistently: top -> bottom -> top -> bottom -> top (crash on third navigation to top).

Regression

• Works: @codemirror/view@6.38.6
• Crashes: @codemirror/view@6.39.7

Workaround

Pin @codemirror/view to 6.38.6.

Steps to reproduce

1. Open any CodeMirror editor with a document long enough to require scrolling
2. Press Cmd+Down (go to end)
3. Press Cmd+Up (go to start)
4. Repeat steps 2-3 approximately 3 times
5. Editor crashes

Reproduction link

https://codemirror.net/examples/million/

Use any example with sufficient content, then press Cmd+Down / Cmd+Up repeatedly.

Also reproduced on the official CodeMirror website examples.

Browser and platform

Chromium Engine Version 143.0.7499.147, Safari Version 18.5 (20621.2.5.11.8), Firefox 144.0.2 (aarch64)

Reproduction link

https://codemirror.net/examples/million/

[marijnh]

Thanks for the report. I could find the issue, and attached patch should fix it.