Save config files atomically

Fixes #506.

In PR #377 (save GlobalPrefs atomically), I created a new codepath by
passing a file into yaml.dump. Unfortunately I forgot to mark it as
UTF-8 (regressing #311). This breaks saving settings after opening a
config in a Unicode folder.

To prevent this from recurring, I restructured the code to always pass a
Path into yaml.dump(), and write the file atomically.

CHANGELOG.md

@@ -14,6 +14,8 @@
 ### Changelog
 
 - When opening missing file via CLI, show dialog rather than crashing (#499)
+- Fix saving global settings after opening config in Unicode folder (#507)
+- Save config files atomically (#507)
 
 ## 0.10.1
 

corrscope/config.py

@@ -19,10 +19,10 @@ from typing import (
     Any,
     TextIO,
     Union,
-    IO,
 )
 
 import attr
+from atomicwrites import atomic_write
 from ruamel.yaml import (
     yaml_object,
     YAML,
@@ -61,9 +61,14 @@ class MyYAML(YAML):
         # https://bitbucket.org/ruamel/yaml/issues/316/unicode-encoding-decoding-errors-on
         # Both are bad, so use UTF-8.
         if isinstance(stream, Path):
-            with stream.open("w", encoding="utf-8") as f:
+            path = stream
+            with atomic_write(path, overwrite=True, encoding="utf-8") as f:
                 self.dump_without_corrupting(data, f, **kwargs)
 
+        elif isinstance(stream, TextIO):
+            # Nobody actually calls dump(..., open()). This branch is never taken.
+            self.dump_without_corrupting(data, stream, **kwargs)
+
         elif stream is None:
             # Possibly only called in unit tests, not in production.
             stream = StringIO()
@@ -71,8 +76,9 @@ class MyYAML(YAML):
             return stream.getvalue()
 
         else:
-            # with atomic_write(...) as f: dump(..., f)
-            self.dump_without_corrupting(data, stream, **kwargs)
+            raise TypeError(
+                f"stream must be {{Path, TextIO=open(), None}}, but is {type(stream)}"
+            )
 
     def dump_without_corrupting(self, *args, **kwargs):
         YAML.dump(self, *args, **kwargs)

corrscope/settings/global_prefs.py

@@ -1,8 +1,6 @@
 from typing import *
 
 import attr
-from atomicwrites import atomic_write
-
 from corrscope.config import DumpableAttrs, yaml
 from corrscope.settings import paths
 
@@ -75,5 +73,4 @@ def load_prefs() -> GlobalPrefs:
 
 
 def dump_prefs(pref: GlobalPrefs) -> None:
-    with atomic_write(_PREF_PATH, overwrite=True, encoding="utf-8") as f:
-        yaml.dump(pref, f)
+    yaml.dump(pref, _PREF_PATH)