Make targets writeable before removal on Windows (fixes #1610)

internal/osutil/osutil.go

@@ -88,6 +88,20 @@ func InWritableDir(fn func(string) error, path string) error {
 	return fn(path)
 }
 
+// On Windows, removes the read-only attribute from the target prior deletion.
+func Remove(path string) error {
+	if runtime.GOOS == "windows" {
+		info, err := os.Stat(path)
+		if err != nil {
+			return err
+		}
+		if info.Mode()&0200 == 0 {
+			os.Chmod(path, 0700)
+		}
+	}
+	return os.Remove(path)
+}
+
 func ExpandTilde(path string) (string, error) {
 	if path == "~" {
 		return getHomeDir()

internal/osutil/osutil_test.go

@@ -8,6 +8,7 @@ package osutil_test
 
 import (
 	"os"
+	"runtime"
 	"testing"
 
 	"github.com/syncthing/syncthing/internal/osutil"
@@ -68,3 +69,97 @@ func TestInWriteableDir(t *testing.T) {
 		t.Error("testdata/file/foo returned nil error")
 	}
 }
+
+func TestInWritableDirWindowsRemove(t *testing.T) {
+	if runtime.GOOS != "windows" {
+		t.Skipf("Tests not required")
+		return
+	}
+
+	err := os.RemoveAll("testdata")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll("testdata")
+
+	create := func(name string) error {
+		fd, err := os.Create(name)
+		if err != nil {
+			return err
+		}
+		fd.Close()
+		return nil
+	}
+
+	os.Mkdir("testdata", 0700)
+
+	os.Mkdir("testdata/windows", 0500)
+	os.Mkdir("testdata/windows/ro", 0500)
+	create("testdata/windows/ro/readonly")
+	os.Chmod("testdata/windows/ro/readonly", 0500)
+
+	for _, path := range []string{"testdata/windows/ro/readonly", "testdata/windows/ro", "testdata/windows"} {
+		err := os.Remove(path)
+		if err == nil {
+			t.Errorf("Expected error %s", path)
+		}
+	}
+
+	for _, path := range []string{"testdata/windows/ro/readonly", "testdata/windows/ro", "testdata/windows"} {
+		err := osutil.InWritableDir(osutil.Remove, path)
+		if err != nil {
+			t.Errorf("Unexpected error %s: %s", path, err)
+		}
+	}
+}
+
+func TestInWritableDirWindowsRename(t *testing.T) {
+	if runtime.GOOS != "windows" {
+		t.Skipf("Tests not required")
+		return
+	}
+
+	err := os.RemoveAll("testdata")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll("testdata")
+
+	create := func(name string) error {
+		fd, err := os.Create(name)
+		if err != nil {
+			return err
+		}
+		fd.Close()
+		return nil
+	}
+
+	os.Mkdir("testdata", 0700)
+
+	os.Mkdir("testdata/windows", 0500)
+	os.Mkdir("testdata/windows/ro", 0500)
+	create("testdata/windows/ro/readonly")
+	os.Chmod("testdata/windows/ro/readonly", 0500)
+
+	for _, path := range []string{"testdata/windows/ro/readonly", "testdata/windows/ro", "testdata/windows"} {
+		err := os.Rename(path, path+"new")
+		if err == nil {
+			t.Errorf("Expected error %s", path)
+		}
+	}
+
+	rename := func(path string) error {
+		return osutil.Rename(path, path+"new")
+	}
+
+	for _, path := range []string{"testdata/windows/ro/readonly", "testdata/windows/ro", "testdata/windows"} {
+		err := osutil.InWritableDir(rename, path)
+		if err != nil {
+			t.Errorf("Unexpected error %s: %s", path, err)
+		}
+		_, err = os.Stat(path + "new")
+		if err != nil {
+			t.Errorf("Unexpected error %s: %s", path, err)
+		}
+	}
+}