Mapper: Support renaming the file during save() if required

datafiles/mapper.py

@@ -15,7 +15,7 @@
 from . import config, formats, hooks
 from .converters import Converter, List, map_type, resolve
 from .types import Missing, Trilean
-from .utils import display, get_default_field_value, recursive_update, write
+from .utils import display, get_default_field_value, recursive_update, write, remove
 
 
 class Mapper:
@@ -45,6 +45,7 @@ def __init__(
         self._last_load = 0.0
         self._last_data: Dict = {}
         self._root = root
+        self._original_path = self.path
 
     @property
     def classname(self) -> str:
@@ -264,6 +265,14 @@ def save(self, *, include_default_values: Trilean = None, _log=True) -> None:
             self._root.save(include_default_values=include_default_values, _log=_log)
             return
 
+        # Determine whether the attributes that are involved in the path were changed
+        file_rename_required = False
+        with hooks.disabled():  # hooks have to be disabled to prevent infinite loop
+            del self.__dict__["path"]  # invalidate the cached property
+
+            if self.path != self._original_path:
+                file_rename_required = True
+
         if self.path:
             if self.exists and self._frozen:
                 raise dataclasses.FrozenInstanceError(
@@ -279,6 +288,9 @@ def save(self, *, include_default_values: Trilean = None, _log=True) -> None:
             text = self._get_text(include_default_values=include_default_values)
 
         write(self.path, text, display=True)
+        if file_rename_required:
+            remove(self._original_path)
+            self._original_path = self.path
 
         self.modified = False