Handle IO error on document save (#961)

* Add try/except to document replace call
* Try the os.replace command 5 times
* Just use else condition on for loop instead
* Make the exceptions explicitly OSError
* Revert the os.replace loop, as this is not the issue

novelwriter/core/document.py

@@ -162,7 +162,11 @@ class NWDoc():
 
         # If we're here, the file was successfully saved, so we can
         # replace the temp file with the actual file
-        os.replace(docTemp, docPath)
+        try:
+            os.replace(docTemp, docPath)
+        except OSError as exc:
+            self._docError = formatException(exc)
+            return False
 
         self._prevHash = sha256sum(docPath)
         self._currHash = self._prevHash

novelwriter/core/project.py

@@ -715,7 +715,7 @@ class NWProject():
             if os.path.isfile(saveFile):
                 os.replace(saveFile, backFile)
             os.replace(tempFile, saveFile)
-        except Exception as exc:
+        except OSError as exc:
             self.theParent.makeAlert(self.tr(
                 "Failed to save project."
             ), nwAlert.ERROR, exception=exc)

tests/test_core/test_core_document.py

@@ -112,6 +112,18 @@ def testCoreDocument_LoadSave(monkeypatch, mockGUI, nwMinimal):
         assert theDoc.writeDocument(theText) is False
         assert theDoc.getError() == "OSError: Mock OSError"
 
+    theDoc._docError = ""
+    assert theDoc.getError() == ""
+
+    # Cause os.replace() to fail while saving
+    with monkeypatch.context() as mp:
+        mp.setattr("os.replace", causeOSError)
+        assert theDoc.writeDocument(theText) is False
+        assert theDoc.getError() == "OSError: Mock OSError"
+
+    theDoc._docError = ""
+    assert theDoc.getError() == ""
+
     # Saving with no handle
     theDoc._docHandle = None
     assert theDoc.writeDocument(theText) is False