Crashing in goroutine causes terminal to become unresponsive

[JesseAldridge]

package main

import (
	"os"
	"os/exec"

	"github.com/gdamore/tcell"
	"github.com/rivo/tview"
)

func crash() int {
	my_list := []int{1, 2, 3}
	return my_list[5]
}

func main() {
	app := tview.NewApplication()

	app.SetInputCapture(func(event *tcell.EventKey) *tcell.EventKey {
		k := event.Key()
		if k == tcell.KeyEnter {
			go crash()
		}
		return event
	})

	box := tview.NewBox().SetBorder(true).SetTitle("Hello, world!")
	if err := app.SetRoot(box, true).Run(); err != nil {
		panic(err)
	}
}

[rivo]

I tried your source code and it didn't become unresponsive for me (on a Mac). Ctrl-C still stops the program as expected.

A panic in a goroutine will just crash that goroutine. If you want tview to react to a panic (usually, this means shutting down the application), you'll need to propagate the panic to the main goroutine.

This is not really an issue with tview but rather Go's general behaviour. I'll close this for now but will reopen in case we do identify anything that needs to be done in tview.

[JesseAldridge]

Not sure I'm understanding. Here is a gif that will hopefully clarify:

It looks like the issue is actually not that the terminal becomes unresponsive, but that input stops rendering. In that gif I ran the code above (with the bad imports removed), after it crashes I hit a bunch of random keys. Then I type echo "hello". The keystrokes are apparently still being processed by bash, but just not rendering properly. Hitting Ctrl-C doesn't remedy the situation.

So you're saying that after the goroutine crashes the tview gui should continue functioning? That appears not to have happened in my case.

[JesseAldridge]

I'm also on a mac. High Sierra with iterm2.

[rivo]

I didn't say the tview GUI should continue functioning. In fact, I would say you should try to avoid panics in goroutines as the result will be undefined, as you can see. Go writes to stderr when it panics. I don't know how this affects the terminal session but obviously it doesn't in a good way.

You may be able to recover from this by running the reset command.

[JesseAldridge]

Yeah looks like I just need to call app.Stop() and recover from the goroutine.
This works well:

package main

import (
	"github.com/gdamore/tcell"
	"github.com/rivo/tview"
)

func crash(app *tview.Application) int {
	defer func() {
		if r := recover(); r != nil {
			app.Stop()
		}
	}()
	my_list := []int{1, 2, 3}
	return my_list[5]
}

func main() {
	app := tview.NewApplication()

	app.SetInputCapture(func(event *tcell.EventKey) *tcell.EventKey {
		k := event.Key()
		if k == tcell.KeyEnter {
			go crash(app)
		}
		return event
	})

	box := tview.NewBox().SetBorder(true).SetTitle("Hello, world!")
	if err := app.SetRoot(box, true).Run(); err != nil {
		panic(err)
	}
}

[rivo]

Yes, this should be a good way of dealing with it. I think you can even print the panic's callstack after app.Stop().