main: do not print *exec.ExitError for -run (#61)

Instead, rely on the program to output something sensible on
stdout/stderr. Exit with the exit code from the program we ran.

For this we use a local version of *os.ProcessState.ExitStatus()
https://go-review.googlesource.com/c/go/+/125443/ which is due to land
in Go 1.12

exitcode_plan9.go

@@ -0,0 +1,16 @@
+package main
+
+import (
+	"os"
+	"syscall"
+)
+
+// ExitCode returns the exit code of the exited process, or -1
+// if the process hasn't exited or was terminated by a signal.
+func ExitCode(p *os.ProcessState) int {
+	// return -1 if the process hasn't started.
+	if p == nil {
+		return -1
+	}
+	return p.Sys().(syscall.WaitStatus).ExitStatus()
+}

exitcode_posix.go

@@ -0,0 +1,18 @@
+// +build darwin dragonfly freebsd js,wasm linux nacl netbsd openbsd solaris windows
+
+package main
+
+import (
+	"os"
+	"syscall"
+)
+
+// ExitCode returns the exit code of the exited process, or -1
+// if the process hasn't exited or was terminated by a signal.
+func ExitCode(p *os.ProcessState) int {
+	// return -1 if the process hasn't started.
+	if p == nil {
+		return -1
+	}
+	return p.Sys().(syscall.WaitStatus).ExitStatus()
+}

main.go

@@ -54,6 +54,9 @@ func main() {
 
 func main1() int {
 	if err := mainerr(); err != nil {
+		if ee, ok := err.(*exec.ExitError); ok {
+			return ExitCode(ee.ProcessState)
+		}
 		fmt.Fprintln(os.Stderr, err)
 		return 1
 	}

script_test.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"fmt"
+	"io/ioutil"
 	"os"
 	"os/exec"
 	"runtime"
@@ -39,6 +40,41 @@ func (m gobinMain) Run() int {
 	return m.m.Run()
 }
 
+func TestExitCode(t *testing.T) {
+	var err error
+	self, err := os.Executable()
+	if err != nil {
+		t.Fatalf("failed to determine os.Executable: %v", err)
+	}
+
+	temp, err := ioutil.TempDir("", "gobin-exitcode-test")
+	if err != nil {
+		t.Fatalf("failed to create temp directory for home: %v", err)
+	}
+	defer os.RemoveAll(temp)
+
+	cmd := exec.Command(self, "-run", "example.com/fail")
+	cmd.Env = os.Environ()
+	cmd.Env = append(cmd.Env, homeEnv(temp)...)
+	cmd.Env = append(cmd.Env,
+		"GOPROXY="+proxyURL,
+		"TESTSCRIPT_COMMAND=gobin",
+	)
+
+	err = cmd.Run()
+	if err == nil {
+		t.Fatalf("unexpected success")
+	}
+	ee, ok := err.(*exec.ExitError)
+	if !ok {
+		t.Fatalf("expected *exec.ExitError; got %T: %v", err, err)
+	}
+	want := 42
+	if got := ExitCode(ee.ProcessState); want != got {
+		t.Fatalf("expected exit code %v; got %v", want, got)
+	}
+}
+
 func TestScripts(t *testing.T) {
 	var (
 		pathToMod     string // local path to this module
@@ -93,17 +129,8 @@ func TestScripts(t *testing.T) {
 				"USERCACHEDIR="+ucd,
 			)
 
-			if runtime.GOOS == "windows" {
-				e.Vars = append(e.Vars,
-					"USERPROFILE="+wd+"\\home",
-					"LOCALAPPDATA="+wd+"\\appdata",
-					"HOME="+wd+"\\home", // match USERPROFILE
-				)
-			} else {
-				e.Vars = append(e.Vars,
-					"HOME="+wd+"/home",
-				)
-			}
+			e.Vars = append(e.Vars, homeEnv(wd)...)
+
 			return nil
 		},
 	}
@@ -112,3 +139,15 @@ func TestScripts(t *testing.T) {
 	}
 	testscript.Run(t, p)
 }
+
+func homeEnv(base string) []string {
+	if runtime.GOOS == "windows" {
+		return []string{
+			"USERPROFILE=" + base + "\\home",
+			"LOCALAPPDATA=" + base + "\\appdata",
+			"HOME=" + base + "\\home", // match USERPROFILE
+		}
+	} else {
+		return []string{"HOME=" + base + "/home"}
+	}
+}

testdata/failing_run.txt

@@ -1,5 +1,5 @@
 ! gobin -run example.com/fail
 stdout '^This will fail$'
-stderr '^exit status 42$'
+stderr '^It''s bad$'
 
 

testdata/mod/example.com_fail_v1.0.0.txt

@@ -14,6 +14,7 @@ import "fmt"
 import "os"
 
 func main() {
-  fmt.Println("This will fail")
-  os.Exit(42)
+	fmt.Println("This will fail")
+	fmt.Fprintln(os.Stderr, "It's bad")
+	os.Exit(42)
 }