atomic_write context to save configs first to temp file, then move

Should prevent corruption of files

src/octoprint/printer/profile.py

@@ -329,12 +329,14 @@ class PrinterProfileManager(object):
 		if os.path.exists(path) and not allow_overwrite:
 			raise SaveError("Profile %s already exists and not allowed to overwrite" % profile["id"])
 
+		from octoprint.util import atomic_write
 		import yaml
-		with open(path, "wb") as f:
-			try:
+		try:
+			with atomic_write(path, "wb") as f:
 				yaml.safe_dump(profile, f, default_flow_style=False, indent="  ", allow_unicode=True)
-			except Exception as e:
-				raise SaveError("Cannot save profile %s: %s" % (profile["id"], str(e)))
+		except Exception as e:
+			self._logger.exception("Error while trying to save profile %s" % profile["id"])
+			raise SaveError("Cannot save profile %s: %s" % (profile["id"], str(e)))
 
 	def _remove_from_path(self, path):
 		try:

src/octoprint/settings.py

@@ -798,11 +798,17 @@ class Settings(object):
 		if not self._dirty and not force:
 			return False
 
-		with open(self._configfile, "wb") as configFile:
-			yaml.safe_dump(self._config, configFile, default_flow_style=False, indent="    ", allow_unicode=True)
-			self._dirty = False
-		self.load()
-		return True
+		from octoprint.util import atomic_write
+		try:
+			with atomic_write(self._configfile, "wb", prefix="octoprint-config-", suffix=".yaml") as configFile:
+				yaml.safe_dump(self._config, configFile, default_flow_style=False, indent="    ", allow_unicode=True)
+				self._dirty = False
+		except:
+			self._logger.exception("Error while saving config.yaml!")
+			raise
+		else:
+			self.load()
+			return True
 
 	@property
 	def last_modified(self):

src/octoprint/util/__init__.py

@@ -17,6 +17,7 @@ import shutil
 import threading
 from functools import wraps
 import warnings
+import contextlib
 
 
 logger = logging.getLogger(__name__)
@@ -513,6 +514,15 @@ def address_for_client(host, port):
 		except:
 			continue
 
+
+@contextlib.contextmanager
+def atomic_write(filename, mode="w+b", prefix="tmp", suffix=""):
+	temp_config = tempfile.NamedTemporaryFile(mode=mode, prefix=prefix, suffix=suffix, delete=False)
+	yield temp_config
+	temp_config.close()
+	shutil.move(temp_config.name, filename)
+
+
 class RepeatedTimer(threading.Thread):
 	"""
 	This class represents an action that should be run repeatedly in an interval. It is similar to python's