Added msys2/cygwin terminal detection support

log/term/terminal_windows.go

@@ -8,15 +8,23 @@
 package term
 
 import (
+	"bytes"
+	"encoding/binary"
 	"io"
+	"regexp"
 	"syscall"
 	"unsafe"
+
+	"golang.org/x/sys/windows"
+	"golang.org/x/text/encoding/unicode"
 )
 
 var kernel32 = syscall.NewLazyDLL("kernel32.dll")
 
 var (
-	procGetConsoleMode = kernel32.NewProc("GetConsoleMode")
+	procGetFileInformationByHandleEx = kernel32.NewProc("GetFileInformationByHandleEx")
+	FileNameInfo                     = 0x02
+	msysPipeNameRegex                = regexp.MustCompile(`\\(cygwin|msys)-\w+-pty\d?-(to|from)-master`)
 )
 
 // IsTerminal returns true if w writes to a terminal.
@@ -25,7 +33,49 @@ func IsTerminal(w io.Writer) bool {
 	if !ok {
 		return false
 	}
+
+	handle := windows.Handle(fw.Fd())
 	var st uint32
-	r, _, e := syscall.Syscall(procGetConsoleMode.Addr(), 2, fw.Fd(), uintptr(unsafe.Pointer(&st)), 0)
-	return r != 0 && e == 0
+	err := windows.GetConsoleMode(handle, &st)
+
+	if err == nil {
+		return true
+	}
+
+	// The terminal is not a cmd.exe terminal, let's try to detect MSYS2 terminals.
+
+	// MSYS2 terminal reports as a pipe.
+	if ft, err := windows.GetFileType(handle); err != nil || ft != windows.FILE_TYPE_PIPE {
+		return false
+	}
+
+	// MSYS2/Cygwin terminal's name looks like: \msys-dd50a72ab4668b33-pty2-to-master
+	data := make([]byte, 256, 256)
+
+	r, _, e := syscall.Syscall6(
+		procGetFileInformationByHandleEx.Addr(),
+		4,
+		fw.Fd(),
+		uintptr(FileNameInfo),
+		uintptr(unsafe.Pointer(&data[0])),
+		uintptr(len(data)),
+		0,
+		0,
+	)
+
+	if r != 0 && e == 0 {
+		var size uint32
+		binary.Read(bytes.NewBuffer(data[:4]), binary.LittleEndian, &size)
+
+		utf16Decoder := unicode.UTF16(unicode.LittleEndian, unicode.IgnoreBOM).NewDecoder()
+		name, err := utf16Decoder.Bytes(data[4 : size+4])
+
+		if err != nil {
+			return false
+		}
+
+		return msysPipeNameRegex.Match(name)
+	}
+
+	return false
 }

log/term/terminal_windows_test.go

@@ -0,0 +1,37 @@
+package term
+
+import (
+	"fmt"
+	"testing"
+
+	"golang.org/x/sys/windows"
+)
+
+// +build windows
+
+type myWriter struct {
+	fd uintptr
+}
+
+func (w *myWriter) Write(p []byte) (int, error) {
+	return 0, fmt.Errorf("not implemented")
+}
+
+func (w *myWriter) Fd() uintptr {
+	return w.fd
+}
+
+func TestIsTerminal(t *testing.T) {
+	handle, err := windows.GetStdHandle(windows.STD_OUTPUT_HANDLE)
+
+	if err != nil {
+		panic(err)
+	}
+
+	writer := &myWriter{
+		fd: uintptr(handle),
+	}
+	if !IsTerminal(writer) {
+		t.Errorf("output is supposed to be a terminal")
+	}
+}