all: fix build on plan9

It turns out that the syscall package is not only a problem for
unix vs windows, but also for unix vs plan9.

Thankfully, I forgot that os/exec.ExitError.ExitCode exists,
so at least we can still extract exit status codes on all platforms.

expand/expand.go

@@ -16,7 +16,6 @@ import (
 	"runtime"
 	"strconv"
 	"strings"
-	"syscall"
 
 	"mvdan.cc/sh/v3/pattern"
 	"mvdan.cc/sh/v3/syntax"
@@ -890,9 +889,7 @@ func (cfg *Config) glob(base, pat string) ([]string, error) {
 				// which can be wasteful if we only want to see if it exists,
 				// but at least it's correct in all scenarios.
 				if _, err := cfg.ReadDir2(match); err != nil {
-					const errPathNotFound = syscall.Errno(3) // from syscall/types_windows.go, to avoid a build tag
-					var pathErr *os.PathError
-					if runtime.GOOS == "windows" && errors.As(err, &pathErr) && pathErr.Err == errPathNotFound {
+					if isWindowsErrPathNotFound(err) {
 						// Unfortunately, os.File.Readdir on a regular file on
 						// Windows returns an error that satisfies ErrNotExist.
 						// Luckily, it returns a special "path not found" rather

expand/expand_nonwindows.go

@@ -0,0 +1,8 @@
+// Copyright (c) 2017, Daniel Martí <[email protected]>
+// See LICENSE for licensing information
+
+//go:build !windows
+
+package expand
+
+func isWindowsErrPathNotFound(error) bool { return false }

expand/expand_windows.go

@@ -0,0 +1,15 @@
+// Copyright (c) 2017, Daniel Martí <[email protected]>
+// See LICENSE for licensing information
+
+package expand
+
+import (
+	"errors"
+	"os"
+	"syscall"
+)
+
+func isWindowsErrPathNotFound(err error) bool {
+	var pathErr *os.PathError
+	return errors.As(err, &pathErr) && pathErr.Err == syscall.ERROR_PATH_NOT_FOUND
+}

interp/handler.go

@@ -14,7 +14,6 @@ import (
 	"path/filepath"
 	"runtime"
 	"strings"
-	"syscall"
 	"time"
 
 	"mvdan.cc/sh/v3/expand"
@@ -135,18 +134,15 @@ func DefaultExecHandler(killTimeout time.Duration) ExecHandlerFunc {
 
 		switch err := err.(type) {
 		case *exec.ExitError:
-			// started, but errored - default to 1 if OS
-			// doesn't have exit statuses
-			if status, ok := err.Sys().(syscall.WaitStatus); ok {
-				if status.Signaled() {
-					if ctx.Err() != nil {
-						return ctx.Err()
-					}
-					return NewExitStatus(uint8(128 + status.Signal()))
+			// Windows and Plan9 do not have support for syscall.WaitStatus
+			// with methods like Signaled and Signal, so for those, waitStatus is a no-op.
+			if status, ok := err.Sys().(waitStatus); ok && status.Signaled() {
+				if ctx.Err() != nil {
+					return ctx.Err()
 				}
-				return NewExitStatus(uint8(status.ExitStatus()))
+				return NewExitStatus(uint8(128 + status.Signal()))
 			}
-			return NewExitStatus(1)
+			return NewExitStatus(uint8(err.ExitCode()))
 		case *exec.Error:
 			// did not start
 			fmt.Fprintf(hc.Stderr, "%v\n", err)

interp/os_notunix.go

@@ -28,3 +28,9 @@ func hasPermissionToDir(string) bool {
 func (r *Runner) unTestOwnOrGrp(ctx context.Context, op syntax.UnTestOperator, x string) bool {
 	panic(fmt.Sprintf("unhandled unary test op: %v", op))
 }
+
+// waitStatus is a no-op on plan9 and windows.
+type waitStatus struct{}
+
+func (waitStatus) Signaled() bool { return false }
+func (waitStatus) Signal() int    { return 0 }

interp/os_unix.go

@@ -43,3 +43,5 @@ func (r *Runner) unTestOwnOrGrp(ctx context.Context, op syntax.UnTestOperator, x
 	gid, _ := strconv.Atoi(u.Gid)
 	return uint32(gid) == info.Sys().(*syscall.Stat_t).Gid
 }
+
+type waitStatus = syscall.WaitStatus