Correctly write line endings to files

vobject uses \r\n as line endings. Writing this to a file is not a problem on Linux and newer versions of MacOS. On Windows \r\r\n gets written to disk and on older versions of MacOS \r\r gets written to disk, because python replaces \n by the system depended line ending.

radicale/storage.py

@@ -391,11 +391,11 @@ class Collection(BaseCollection):
         return os.path.join(filesystem_folder, "collection-root")
 
     @contextmanager
-    def _atomic_write(self, path, mode="w"):
+    def _atomic_write(self, path, mode="w", newline=None):
         directory = os.path.dirname(path)
         tmp = NamedTemporaryFile(
             mode=mode, dir=directory, encoding=self.encoding,
-            delete=False, prefix=".Radicale.tmp-")
+            delete=False, prefix=".Radicale.tmp-", newline=newline)
         try:
             yield tmp
             if self.configuration.getboolean("storage", "fsync"):
@@ -607,7 +607,7 @@ class Collection(BaseCollection):
         path = path_to_filesystem(self._filesystem_path, href)
         if not os.path.isfile(path):
             return None
-        with open(path, encoding=self.encoding) as fd:
+        with open(path, encoding=self.encoding, newline="") as fd:
             text = fd.read()
         last_modified = time.strftime(
             "%a, %d %b %Y %H:%M:%S GMT",
@@ -624,7 +624,7 @@ class Collection(BaseCollection):
         if os.path.exists(path):
             raise ComponentExistsError(href)
         item = Item(self, vobject_item, href)
-        with self._atomic_write(path) as fd:
+        with self._atomic_write(path, newline="") as fd:
             fd.write(item.serialize())
         return item
 
@@ -639,7 +639,7 @@ class Collection(BaseCollection):
         if etag and etag != get_etag(text):
             raise EtagMismatchError(etag, get_etag(text))
         item = Item(self, vobject_item, href)
-        with self._atomic_write(path) as fd:
+        with self._atomic_write(path, newline="") as fd:
             fd.write(item.serialize())
         return item
 
@@ -704,7 +704,7 @@ class Collection(BaseCollection):
                 continue
             path = os.path.join(self._filesystem_path, href)
             if os.path.isfile(path):
-                with open(path, encoding=self.encoding) as fd:
+                with open(path, encoding=self.encoding, newline="") as fd:
                     items.append(vobject.readOne(fd.read()))
         if self.get_meta("tag") == "VCALENDAR":
             collection = vobject.iCalendar()