Add support for running sub-processes under a PTY

This is really nice for running programs that output colour, such as
coloured log lines, etc.

I defaulted it to off because some applications when run under a PTY
will attempt to move the cursor around, clear lines, and so on, so it
should be up to the user to decide whether to enable it.

Author: alecthomas

go.mod

@@ -9,4 +9,7 @@ require (
 	gopkg.in/yaml.v3 v3.0.1
 )
 
-require github.com/mattn/go-isatty v0.0.17 // indirect
+require (
+	github.com/creack/pty v1.1.18
+	github.com/mattn/go-isatty v0.0.17 // indirect
+)

go.sum

@@ -1,3 +1,5 @@
+github.com/creack/pty v1.1.18 h1:n56/Zwd5o6whRC5PMGretI4IdRLlmBXYNjScPaBgsbY=
+github.com/creack/pty v1.1.18/go.mod h1:MOBLtS5ELjhRRrroQr9kyvTxUAFNvYEK993ew/Vr4O4=
 github.com/joho/godotenv v1.5.1 h1:7eLL/+HRGLY0ldzfGMeQkb7vMd0as4CfYvUVzLqw0N0=
 github.com/joho/godotenv v1.5.1/go.mod h1:f4LDr5Voq0i2e/R5DDNOoa2zzDfwtkZa6DnEwAbqwq4=
 github.com/mattn/go-colorable v0.1.13 h1:fFA4WZxdEF4tXPZVKMLwD8oUnCTTo08duU7wxecdEvA=

main.go

@@ -98,6 +98,9 @@ var exitOnStop = flag.Bool("exit-on-stop", true, "Exit goreman if all subprocess
 // show timestamp in log
 var logTime = flag.Bool("logtime", true, "show timestamp in log")
 
+// use a PTY for all subprocesses
+var usePty = flag.Bool("pty", false, "use a PTY for all subprocesses (noop on Windows)")
+
 var maxProcNameLength = 0
 
 var re = regexp.MustCompile(`\$([a-zA-Z]+[a-zA-Z0-9_]+)`)

proc.go

@@ -17,10 +17,16 @@ func spawnProc(name string, errCh chan<- error) {
 	cs := append(cmdStart, proc.cmdline)
 	cmd := exec.Command(cs[0], cs[1:]...)
 	cmd.Stdin = nil
-	cmd.Stdout = logger
-	cmd.Stderr = logger
 	cmd.SysProcAttr = procAttrs
 
+	if err := startPTY(logger, cmd); err != nil {
+		select {
+		case errCh <- err:
+		default:
+		}
+		fmt.Fprintf(logger, "Failed to open pty for %s: %s\n", name, err)
+		return
+	}
 	if proc.setPort {
 		cmd.Env = append(os.Environ(), fmt.Sprintf("PORT=%d", proc.port))
 		fmt.Fprintf(logger, "Starting %s on port %d\n", name, proc.port)

proc_posix.go

@@ -4,9 +4,13 @@
 package main
 
 import (
+	"fmt"
+	"io"
 	"os"
+	"os/exec"
 	"os/signal"
 
+	"github.com/creack/pty"
 	"golang.org/x/sys/unix"
 )
 
@@ -51,3 +55,21 @@ func notifyCh() <-chan os.Signal {
 	signal.Notify(sc, sigterm, sigint, sighup)
 	return sc
 }
+
+func startPTY(logger *clogger, cmd *exec.Cmd) error {
+	if *usePty {
+		p, t, err := pty.Open()
+		if err != nil {
+			return fmt.Errorf("failed to open PTY: %w", err)
+		}
+		defer p.Close()
+		defer t.Close()
+		cmd.Stdout = t
+		cmd.Stderr = t
+		go io.Copy(logger, p)
+	} else {
+		cmd.Stdout = logger
+		cmd.Stderr = logger
+	}
+	return nil
+}

proc_windows.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"os"
+	"os/exec"
 	"os/signal"
 	"syscall"
 
@@ -63,3 +64,9 @@ func notifyCh() <-chan os.Signal {
 	signal.Notify(sc, os.Interrupt)
 	return sc
 }
+
+// This is a no-op on Windows.
+func startPTY(logger *clogger, cmd *exec.Cmd) error {
+	cmd.Stdout = logger
+	cmd.Stderr = logger
+}