terminal: fix race conditions on access to cmd

Upgrade tcell-term to v0.2.0

Use Start method from tcell-term. This prevents aerc from needing to
wait until the command has started to continue. The tcell-term start
method blocks until the command is started, similar to cmd.Start. By
doing so, we prevent a race condition between aerc and tcell-term on
access to cmd.Process.

Remove cleanup of cmd, this is all already handled by tcell-term when
Close is called.

Signed-off-by: Tim Culverhouse <tim@timculverhouse.com>
Acked-by: Robin Jarry <robin@jarry.cc>

go.mod

@@ -3,7 +3,7 @@ module git.sr.ht/~rjarry/aerc
 go 1.16
 
 require (
-	git.sr.ht/~rockorager/tcell-term v0.1.1-0.20220920200206-237e095b9b99
+	git.sr.ht/~rockorager/tcell-term v0.2.0
 	git.sr.ht/~sircmpwn/getopt v1.0.0
 	github.com/ProtonMail/go-crypto v0.0.0-20211221144345-a4f6767435ab
 	github.com/arran4/golang-ical v0.0.0-20220517104411-fd89fefb0182

go.sum

@@ -62,8 +62,8 @@ cloud.google.com/go/storage v1.10.0/go.mod h1:FLPqc6j+Ki4BU591ie1oL6qBQGu2Bl/tZ9
 cloud.google.com/go/storage v1.14.0/go.mod h1:GrKmX003DSIwi9o29oFT7YDnHYwZoctc3fOKtUw0Xmo=
 contrib.go.opencensus.io/exporter/stackdriver v0.13.4/go.mod h1:aXENhDJ1Y4lIg4EUaVTwzvYETVNZk10Pu26tevFKLUc=
 dmitri.shuralyov.com/gpu/mtl v0.0.0-20190408044501-666a987793e9/go.mod h1:H6x//7gZCb22OMCxBHrMx7a5I7Hp++hsVxbQ4BYO7hU=
-git.sr.ht/~rockorager/tcell-term v0.1.1-0.20220920200206-237e095b9b99 h1:THSvF4k9Svq/dp9xZ8MgZ6d0FW5+GrXNUOj+YqfeqIY=
+git.sr.ht/~rockorager/tcell-term v0.2.0 h1:aiRmFm6FLqdZOKVUYNumh0K1n7meaebU4BvzVGa1LNA=
-git.sr.ht/~rockorager/tcell-term v0.1.1-0.20220920200206-237e095b9b99/go.mod h1:0CEvSJrV0ItwHlPHSmkxd5egiuUtpvGnnCsqzV02BN4=
+git.sr.ht/~rockorager/tcell-term v0.2.0/go.mod h1:0CEvSJrV0ItwHlPHSmkxd5egiuUtpvGnnCsqzV02BN4=
 git.sr.ht/~sircmpwn/getopt v1.0.0 h1:/pRHjO6/OCbBF4puqD98n6xtPEgE//oq5U8NXjP7ROc=
 git.sr.ht/~sircmpwn/getopt v1.0.0/go.mod h1:wMEGFFFNuPos7vHmWXfszqImLppbc0wEhh6JBfJIUgw=
 github.com/Antonboom/errname v0.1.7 h1:mBBDKvEYwPl4WFFNwec1CZO096G6vzK9vvDQzAwkako=

widgets/terminal.go

@@ -42,24 +42,9 @@ func (term *Terminal) Close(err error) {
 	if term.closed {
 		return
 	}
-	// Stop receiving events
-	term.vterm.Unwatch(term)
-	if term.cmd != nil && term.cmd.Process != nil {
-		err := term.cmd.Process.Kill()
-		if err != nil {
-			logging.Warnf("failed to kill process: %v", err)
-		}
-		// Race condition here, check if cmd exists. If process exits
-		// fast, this could by nil and panic
-		if term.cmd != nil {
-			err = term.cmd.Wait()
-		}
-		if err != nil {
-			logging.Warnf("failed for wait for process to terminate: %v", err)
-		}
-		term.cmd = nil
-	}
 	if term.vterm != nil {
+		// Stop receiving events
+		term.vterm.Unwatch(term)
 		term.vterm.Close()
 	}
 	if !term.closed && term.OnClose != nil {
@@ -96,25 +81,14 @@ func (term *Terminal) Draw(ctx *ui.Context) {
 	term.ctx = ctx // gross
 	term.vterm.SetView(ctx.View())
 	if !term.running && !term.closed && term.cmd != nil {
-		go func() {
+		term.vterm.Watch(term)
-			defer logging.PanicHandler()
+		attr := &syscall.SysProcAttr{Setsid: true, Setctty: true, Ctty: 1}
-			term.vterm.Watch(term)
+		if err := term.vterm.StartWithAttrs(term.cmd, attr); err != nil {
-			attr := &syscall.SysProcAttr{Setsid: true, Setctty: true, Ctty: 1}
+			logging.Errorf("error running terminal: %w", err)
-			if err := term.vterm.RunWithAttrs(term.cmd, attr); err != nil {
+			term.Close(err)
-				logging.Errorf("error running terminal: %w", err)
+			return
-				term.Close(err)
-				term.running = false
-				return
-			}
-			term.running = false
-			term.Close(nil)
-		}()
-		for {
-			if term.cmd.Process != nil {
-				term.running = true
-				break
-			}
 		}
+		term.running = true
 		if term.OnStart != nil {
 			term.OnStart()
 		}
@@ -193,6 +167,8 @@ func (term *Terminal) HandleEvent(ev tcell.Event) bool {
 		if term.OnTitle != nil {
 			term.OnTitle(ev.Title())
 		}
+	case *tcellterm.EventClosed:
+		term.Close(nil)
 	}
 	return false
 }