Cannot read property 'numPiecesPresent' of undefined

[feross]

What version of WebTorrent Desktop? (See the 'About WebTorrent' menu)

0.8.1

What operating system and version?

OS X latest

What did you do?

Add a torrent

What did you expect to happen?

It starts.

What actually happened?

rendering error: Cannot read property 'numPiecesPresent' of undefined
TypeError: Cannot read property 'numPiecesPresent' of undefined
at renderFileRow (/Applications/WebTorrent.app/Contents/Resources/app.asar/renderer/views/home.js:227:24)
at torrentSummary.files.map.sort.map (/Applications/WebTorrent.app/Contents/Resources/app.asar/renderer/views/home.js:200:26)
at Array.map (native)
at renderTorrentDetails (/Applications/WebTorrent.app/Contents/Resources/app.asar/renderer/views/home.js:200:10)
at renderTorrent (/Applications/WebTorrent.app/Contents/Resources/app.asar/renderer/views/home.js:51:24)
at TorrentList.state.saved.torrents.map (/Applications/WebTorrent.app/Contents/Resources/app.asar/renderer/views/home.js:12:25)
at Array.map (native)
at Object.TorrentList as home
at getView (/Applications/WebTorrent.app/Contents/Resources/app.asar/renderer/views/app.js:81:20)
at App (/Applications/WebTorrent.app/Contents/Resources/app.asar/renderer/views/app.js:44:30)
main.js:470 webtorrent: sent wt-save-torrent-file
main.js:470 webtorrent: sent wt-generate-torrent-poster
main.js:470 webtorrent: got wt-progress
/Applications/WebTorrent.app/Contents/Resources/app.asar/node_modules/raf/index.js:74 Uncaught TypeError: Cannot read property 'ownerDocument' of null

[bnjmnt4n]

I've gotten this error before (since a few versions back), but I'm not too sure why. If I read the code correctly, the code that accesses numPiecesPresent shouldn't be run if the torrent isn't ready yet.

[mathiasvr]

This seems to happen if the torrent is expanded too fast, i.e. renderFileRow gets called before the wt-progress event. This especially becomes a problem when the torrent is expanded initially as it's added. I don't know why this would be the case, but when i tested it, if I removed a torrent when it was expanded and added it again it would still be expanded and often cause this crash.

A simple fix might be to null-check torrentSummary.progress.files[index] at this line, which seems alright since we are already checking the progress and files properties. However a more general way of determining the ready state of a torrent seems ideal.

[feross]

Fixed the immediate issue using @mathiasvr's suggestion in PR #757.