talm dashboard / edit under non-tty: panic / hang instead of clean refusal

[lexfrei]

Problem

talm dashboard --nodes $NODE --endpoints $NODE under a non-tty stdin panics in gdamore/tcell rather than failing gracefully with a "needs an interactive terminal" hint.

Reproduction

timeout 3 talm dashboard --nodes $NODE --endpoints $NODE < /dev/null

Output:

panic: close of nil channel

goroutine 150 [running]:
github.com/gdamore/tcell/v2.(*tScreen).finish(...)
        /Users/lex/go/pkg/mod/github.com/gdamore/tcell/v2@v2.13.8/tscreen.go:374
...
exit: 2

The panic comes from tcell's terminal teardown after init refuses to allocate a tty. Upstream issue, but the talm wrapper has the contextual information to refuse earlier with a friendly hint instead.

Expected

pkg/commands/talosctl_wrapper.go (or the dashboard subcommand if it lives in talm) detects non-tty stdin (the same term.IsTerminal(int(os.Stdin.Fd())) check we use for init --update post-#174) and returns:

error: talm dashboard requires an interactive terminal (stdin is not a tty)
hint: run from an attached shell. Scripted use: talm get / talm logs cover most of the dashboard's data.

Cost: a few-line guard. Currently the operator sees a Go stack trace that suggests a bug.

Why this matters

talm dashboard is a popular discovery tool — operators run it locally to inspect a cluster. Some IDE terminals (VS Code's integrated terminal in some configurations, tmux+ssh pipes) present as non-tty under quirky setups. The panic looks like a talm crash, not a misconfiguration.

Same guard would apply to talm edit machineconfig (which currently hangs forever instead of erroring).

Surfaced during the dev17 manual test plan exercise.