The input isn't verified before using epoll on it

[cardil]

Describe the bug

Bubbletea doesn't validate given input, before trying to use epoll on it:

bubbletea/tty.go

Line 55 in 7199a7f

p.cancelReader, err = newInputReader(p.input)

When running processes, Golang (maybe other langs as well?) gives by default the /dev/null as the stdin.

This in turn causes a cryptic epoll error, as the /dev/null doesn't support epoll:

error creating cancelreader: add reader to epoll interest list

You could use muesli/cancelreader#13 to see the underlying syscall.Errno: EPERM. Looking at epoll_ctl(2), the EPERM is returned if:

The target file fd does not support epoll. This error can occur if fd refers to, for example, a regular file or a directory.

Setup

Please complete the following information along with version numbers, if applicable.

• OS: Linux
• Shell: zsh
• Terminal Emulator: Tilix
• Terminal Multiplexer: none

To Reproduce

Steps to reproduce the behavior:

1. Checkout the repro: https://github.com/cardil/bubbletea-964
2. Run test: go test -count=1 ./spin2sec_test.go
3. You should see TestSpin2SecFailing test failing, with error:

   error creating cancelreader: add reader with descriptor 0 to epoll interest list: operation not permitted
   

Expected behavior

Bubbletea should address a common case of having /dev/null as input, and not feed it to epoll-based reader.

Walk around

To walk away of this problem, one might consider giving an empty buffer as process stdin. See, an example: wavesoftware/go-magetasks@7496084.

[cardil]

This (most likely) causes the #797

[cardil]

The error could be evidenced, here as well:

• https://github.com/wavesoftware/go-magetasks/actions/runs/8421235343/job/23057714545?pr=44#step:5:79
• https://github.com/wavesoftware/go-magetasks/actions/runs/8422982644/job/23063551961#step:5:79

[cardil]

FYI: In Knative we walk around this issue with this function: https://github.com/knative/client-pkg/blob/ca64d2dc74eb7189060b3e39399d317ea402e35c/pkg/output/tui/bubbletea964.go#L30-L49