Merge branch 'pr-1410'

* pr-1410:
  Add test for osutil.InWritableDir
  Exit and error if the target is not a directory

internal/osutil/osutil.go

@@ -69,7 +69,14 @@ func Copy(from, to string) (err error) {
 // containing `path` is writable for the duration of the call.
 func InWritableDir(fn func(string) error, path string) error {
 	dir := filepath.Dir(path)
-	if info, err := os.Stat(dir); err == nil && info.IsDir() && info.Mode()&0200 == 0 {
+	info, err := os.Stat(dir)
+	if err != nil {
+		return err
+	}
+	if !info.IsDir() {
+		return errors.New("Not a directory: " + path)
+	}
+	if info.Mode()&0200 == 0 {
 		// A non-writeable directory (for this user; we assume that's the
 		// relevant part). Temporarily change the mode so we can delete the
 		// file or directory inside it.

internal/osutil/osutil_test.go

@@ -15,4 +15,65 @@
 
 package osutil_test
 
-// Empty test file to generate 0% coverage rather than no coverage
+import (
+	"os"
+	"testing"
+
+	"github.com/syncthing/syncthing/internal/osutil"
+)
+
+func TestInWriteableDir(t *testing.T) {
+	err := os.RemoveAll("testdata")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll("testdata")
+
+	os.Mkdir("testdata", 0700)
+	os.Mkdir("testdata/rw", 0700)
+	os.Mkdir("testdata/ro", 0500)
+
+	create := func(name string) error {
+		fd, err := os.Create(name)
+		if err != nil {
+			return err
+		}
+		fd.Close()
+		return nil
+	}
+
+	// These should succeed
+
+	err = osutil.InWritableDir(create, "testdata/file")
+	if err != nil {
+		t.Error("testdata/file:", err)
+	}
+	err = osutil.InWritableDir(create, "testdata/rw/foo")
+	if err != nil {
+		t.Error("testdata/rw/foo:", err)
+	}
+	err = osutil.InWritableDir(os.Remove, "testdata/rw/foo")
+	if err != nil {
+		t.Error("testdata/rw/foo:", err)
+	}
+
+	err = osutil.InWritableDir(create, "testdata/ro/foo")
+	if err != nil {
+		t.Error("testdata/ro/foo:", err)
+	}
+	err = osutil.InWritableDir(os.Remove, "testdata/ro/foo")
+	if err != nil {
+		t.Error("testdata/ro/foo:", err)
+	}
+
+	// These should not
+
+	err = osutil.InWritableDir(create, "testdata/nonexistent/foo")
+	if err == nil {
+		t.Error("testdata/nonexistent/foo returned nil error")
+	}
+	err = osutil.InWritableDir(create, "testdata/file/foo")
+	if err == nil {
+		t.Error("testdata/file/foo returned nil error")
+	}
+}