os/exec: ignore some pipe write errors on windows

This change is windows version of CL 12152.
It also extends test to cover scenarios reported on issue #20445.
Some source files copied and renamed to make code clearer.

Fixes #20445

Change-Id: Idd2f636f27c6bd5cfe98017ba2df911358263382
Reviewed-on: https://go-review.googlesource.com/43910
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/os/exec/exec_test.go

@@ -877,18 +877,30 @@ func TestHelperProcess(*testing.T) {
 	}
 }
 
+type delayedInfiniteReader struct{}
+
+func (delayedInfiniteReader) Read(b []byte) (int, error) {
+	time.Sleep(100 * time.Millisecond)
+	for i := range b {
+		b[i] = 'x'
+	}
+	return len(b), nil
+}
+
 // Issue 9173: ignore stdin pipe writes if the program completes successfully.
 func TestIgnorePipeErrorOnSuccess(t *testing.T) {
 	testenv.MustHaveExec(t)
 
-	// We really only care about testing this on Unixy things.
+	// We really only care about testing this on Unixy and Windowsy things.
-	if runtime.GOOS == "windows" || runtime.GOOS == "plan9" {
+	if runtime.GOOS == "plan9" {
 		t.Skipf("skipping test on %q", runtime.GOOS)
 	}
 
+	testWith := func(r io.Reader) func(*testing.T) {
+		return func(t *testing.T) {
 			cmd := helperCommand(t, "echo", "foo")
 			var out bytes.Buffer
-	cmd.Stdin = strings.NewReader(strings.Repeat("x", 10<<20))
+			cmd.Stdin = r
 			cmd.Stdout = &out
 			if err := cmd.Run(); err != nil {
 				t.Fatal(err)
@@ -897,6 +909,10 @@ func TestIgnorePipeErrorOnSuccess(t *testing.T) {
 				t.Errorf("output = %q; want %q", got, want)
 			}
 		}
+	}
+	t.Run("10MB", testWith(strings.NewReader(strings.Repeat("x", 10<<20))))
+	t.Run("Infinite", testWith(delayedInfiniteReader{}))
+}
 
 type badWriter struct{}
 

src/os/exec/exec_unix.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !plan9
+// +build !plan9,!windows
 
 package exec
 

src/os/exec/exec_windows.go

@@ -0,0 +1,23 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package exec
+
+import (
+	"os"
+	"syscall"
+)
+
+func init() {
+	skipStdinCopyError = func(err error) bool {
+		// Ignore ERROR_BROKEN_PIPE and ERROR_NO_DATA errors copying
+		// to stdin if the program completed successfully otherwise.
+		// See Issue 20445.
+		const _ERROR_NO_DATA = syscall.Errno(0xe8)
+		pe, ok := err.(*os.PathError)
+		return ok &&
+			pe.Op == "write" && pe.Path == "|1" &&
+			(pe.Err == syscall.ERROR_BROKEN_PIPE || pe.Err == _ERROR_NO_DATA)
+	}
+}