Handle long filenames on Windows (fixes #1295)

internal/config/config.go

@@ -15,6 +15,7 @@ import (
 	"os"
 	"path/filepath"
 	"reflect"
+	"runtime"
 	"sort"
 	"strconv"
 	"strings"
@@ -70,7 +71,7 @@ func (orig Configuration) Copy() Configuration {
 
 type FolderConfiguration struct {
 	ID              string                      `xml:"id,attr" json:"id"`
-	Path            string                      `xml:"path,attr" json:"path"`
+	RawPath         string                      `xml:"path,attr" json:"path"`
 	Devices         []FolderDeviceConfiguration `xml:"device" json:"devices"`
 	ReadOnly        bool                        `xml:"ro,attr" json:"readOnly"`
 	RescanIntervalS int                         `xml:"rescanIntervalS,attr" json:"rescanIntervalS"`
@@ -94,9 +95,37 @@ func (orig FolderConfiguration) Copy() FolderConfiguration {
 	return c
 }
 
+func (f FolderConfiguration) Path() string {
+	// This is intentionally not a pointer method, because things like
+	// cfg.Folders["default"].Path() should be valid.
+
+	// Attempt tilde expansion; leave unchanged in case of error
+	if path, err := osutil.ExpandTilde(f.RawPath); err == nil {
+		f.RawPath = path
+	}
+
+	// Attempt absolutification; leave unchanged in case of error
+	if !filepath.IsAbs(f.RawPath) {
+		// Abs() looks like a fairly expensive syscall on Windows, while
+		// IsAbs() is a whole bunch of string mangling. I think IsAbs() may be
+		// somewhat faster in the general case, hence the outer if...
+		if path, err := filepath.Abs(f.RawPath); err == nil {
+			f.RawPath = path
+		}
+	}
+
+	// Attempt to enable long filename support on Windows. We may still not
+	// have an absolute path here if the previous steps failed.
+	if runtime.GOOS == "windows" && filepath.IsAbs(f.RawPath) && !strings.HasPrefix(f.RawPath, `\\`) {
+		return `\\?\` + f.RawPath
+	}
+
+	return f.RawPath
+}
+
 func (f *FolderConfiguration) CreateMarker() error {
 	if !f.HasMarker() {
-		marker := filepath.Join(f.Path, ".stfolder")
+		marker := filepath.Join(f.Path(), ".stfolder")
 		fd, err := os.Create(marker)
 		if err != nil {
 			return err
@@ -109,7 +138,7 @@ func (f *FolderConfiguration) CreateMarker() error {
 }
 
 func (f *FolderConfiguration) HasMarker() bool {
-	_, err := os.Stat(filepath.Join(f.Path, ".stfolder"))
+	_, err := os.Stat(filepath.Join(f.Path(), ".stfolder"))
 	if err != nil {
 		return false
 	}
@@ -285,7 +314,7 @@ func (cfg *Configuration) prepare(myID protocol.DeviceID) {
 	for i := range cfg.Folders {
 		folder := &cfg.Folders[i]
 
-		if len(folder.Path) == 0 {
+		if len(folder.RawPath) == 0 {
 			folder.Invalid = "no directory configured"
 			continue
 		}
@@ -296,7 +325,7 @@ func (cfg *Configuration) prepare(myID protocol.DeviceID) {
 		// C:\somedir\ ->  C:\somedir\\   ->  C:\somedir
 		// This way in the tests, we get away without OS specific separators
 		// in the test configs.
-		folder.Path = filepath.Dir(folder.Path + string(filepath.Separator))
+		folder.RawPath = filepath.Dir(folder.RawPath + string(filepath.Separator))
 
 		if folder.ID == "" {
 			folder.ID = "default"

internal/config/config_test.go

@@ -11,8 +11,10 @@ import (
 	"encoding/json"
 	"fmt"
 	"os"
+	"path/filepath"
 	"reflect"
 	"runtime"
+	"strings"
 	"testing"
 
 	"github.com/syncthing/protocol"
@@ -78,7 +80,7 @@ func TestDeviceConfig(t *testing.T) {
 		expectedFolders := []FolderConfiguration{
 			{
 				ID:              "test",
-				Path:            "testdata",
+				RawPath:         "testdata",
 				Devices:         []FolderDeviceConfiguration{{DeviceID: device1}, {DeviceID: device4}},
 				ReadOnly:        true,
 				RescanIntervalS: 600,
@@ -297,10 +299,10 @@ func TestVersioningConfig(t *testing.T) {
 func TestIssue1262(t *testing.T) {
 	cfg, err := Load("testdata/issue-1262.xml", device4)
 	if err != nil {
-		t.Error(err)
+		t.Fatal(err)
 	}
 
-	actual := cfg.Folders()["test"].Path
+	actual := cfg.Folders()["test"].RawPath
 	expected := "e:"
 	if runtime.GOOS == "windows" {
 		expected = `e:\`
@@ -311,6 +313,51 @@ func TestIssue1262(t *testing.T) {
 	}
 }
 
+func TestWindowsPaths(t *testing.T) {
+	if runtime.GOOS != "windows" {
+		t.Skip("Not useful on non-Windows")
+		return
+	}
+
+	folder := FolderConfiguration{
+		RawPath: `e:\`,
+	}
+
+	expected := `\\?\e:\`
+	actual := folder.Path()
+	if actual != expected {
+		t.Errorf("%q != %q", actual, expected)
+	}
+
+	folder.RawPath = `\\192.0.2.22\network\share`
+	expected = folder.RawPath
+	actual = folder.Path()
+	if actual != expected {
+		t.Errorf("%q != %q", actual, expected)
+	}
+
+	folder.RawPath = `relative\path`
+	expected = folder.RawPath
+	actual = folder.Path()
+	if actual != expected {
+		t.Errorf("%q != %q", actual, expected)
+	}
+}
+
+func TestFolderPath(t *testing.T) {
+	folder := FolderConfiguration{
+		RawPath: "~/tmp",
+	}
+
+	realPath := folder.Path()
+	if !filepath.IsAbs(realPath) {
+		t.Error(realPath, "should be absolute")
+	}
+	if strings.Contains(realPath, "~") {
+		t.Error(realPath, "should not contain ~")
+	}
+}
+
 func TestNewSaveLoad(t *testing.T) {
 	path := "testdata/temp.xml"
 	os.Remove(path)
@@ -391,8 +438,8 @@ func TestRequiresRestart(t *testing.T) {
 
 	newCfg = cfg
 	newCfg.Folders = append(newCfg.Folders, FolderConfiguration{
-		ID:   "t1",
-		Path: "t1",
+		ID:      "t1",
+		RawPath: "t1",
 	})
 	if !ChangeRequiresRestart(cfg, newCfg) {
 		t.Error("Adding a folder requires restart")
@@ -411,7 +458,7 @@ func TestRequiresRestart(t *testing.T) {
 	if ChangeRequiresRestart(cfg, newCfg) {
 		t.Error("No changes done yet")
 	}
-	newCfg.Folders[0].Path = "different"
+	newCfg.Folders[0].RawPath = "different"
 	if !ChangeRequiresRestart(cfg, newCfg) {
 		t.Error("Changing a folder requires restart")
 	}

internal/config/wrapper.go

@@ -159,12 +159,6 @@ func (w *Wrapper) Folders() map[string]FolderConfiguration {
 	if w.folderMap == nil {
 		w.folderMap = make(map[string]FolderConfiguration, len(w.cfg.Folders))
 		for _, fld := range w.cfg.Folders {
-			path, err := osutil.ExpandTilde(fld.Path)
-			if err != nil {
-				l.Warnln("home:", err)
-				continue
-			}
-			fld.Path = path
 			w.folderMap[fld.ID] = fld
 		}
 	}