os: make Stdin.Stat() return ModeCharDevice if Stdin is console

CL 20845 changed Stdin.Stat() so it returns ModeNamedPipe.
But introduced TestStatStdin does not test what Stdin.Stat()
returns when Stdin is console.

This CL adjusts both TestStatStdin and Stdin.Stat
implementations to handle console. Return ModeCharDevice
from Stdin.Stat() when Stdin is console on windows,
just like it does on unix.

Fixes #14853.

Change-Id: I54d73caee2aea45a99618d11600d8e82fe20d0c0
Reviewed-on: https://go-review.googlesource.com/34090Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/os/os_test.go

@@ -1669,6 +1669,17 @@ func TestStatStdin(t *testing.T) {
 		Exit(0)
 	}
 
+	fi, err := Stdin.Stat()
+	if err != nil {
+		t.Fatal(err)
+	}
+	switch mode := fi.Mode(); {
+	case mode&ModeCharDevice != 0:
+	case mode&ModeNamedPipe != 0:
+	default:
+		t.Fatalf("unexpected Stdin mode (%v), want ModeCharDevice or ModeNamedPipe", mode)
+	}
+
 	var cmd *osexec.Cmd
 	if runtime.GOOS == "windows" {
 		cmd = osexec.Command("cmd", "/c", "echo output | "+Args[0]+" -test.run=TestStatStdin")

src/os/stat_windows.go

@@ -31,8 +31,9 @@ func (file *File) Stat() (FileInfo, error) {
 	if err != nil {
 		return nil, &PathError{"GetFileType", file.name, err}
 	}
-	if ft == syscall.FILE_TYPE_PIPE {
-		return &fileStat{name: basename(file.name), pipe: true}, nil
+	switch ft {
+	case syscall.FILE_TYPE_PIPE, syscall.FILE_TYPE_CHAR:
+		return &fileStat{name: basename(file.name), filetype: ft}, nil
 	}
 
 	var d syscall.ByHandleFileInformation
@@ -50,10 +51,10 @@ func (file *File) Stat() (FileInfo, error) {
 			FileSizeHigh:   d.FileSizeHigh,
 			FileSizeLow:    d.FileSizeLow,
 		},
+		filetype: ft,
 		vol:      d.VolumeSerialNumber,
 		idxhi:    d.FileIndexHigh,
 		idxlo:    d.FileIndexLow,
-		pipe:  false,
 	}, nil
 }
 

src/os/types_windows.go

@@ -14,7 +14,7 @@ import (
 type fileStat struct {
 	name     string
 	sys      syscall.Win32FileAttributeData
-	pipe bool
+	filetype uint32 // what syscall.GetFileType returns
 
 	// used to implement SameFile
 	sync.Mutex
@@ -43,8 +43,11 @@ func (fs *fileStat) Mode() (m FileMode) {
 	if fs.sys.FileAttributes&syscall.FILE_ATTRIBUTE_REPARSE_POINT != 0 {
 		m |= ModeSymlink
 	}
-	if fs.pipe {
+	switch fs.filetype {
+	case syscall.FILE_TYPE_PIPE:
 		m |= ModeNamedPipe
+	case syscall.FILE_TYPE_CHAR:
+		m |= ModeCharDevice
 	}
 	return m
 }