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

Author: Tomas Babej

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 = None
 
     @property
     def classname(self) -> str:
@@ -58,7 +59,13 @@ def path(self) -> Optional[Path]:
         path = Path(self._pattern.format(self=self._instance)).expanduser()
         if path.is_absolute() or self._pattern.startswith("./"):
             log.debug(f"Detected static pattern: {path}")
-            return path.resolve()
+
+            resolved_path = path.resolve()
+
+            if self._original_path is None:
+                self._original_path = resolved_path
+
+            return resolved_path
 
         cls = self._instance.__class__
         try:
@@ -69,6 +76,8 @@ def path(self) -> Optional[Path]:
             root = Path.cwd()
 
         path = (root / path).resolve()
+        if self._original_path is None:
+            self._original_path = path
         log.debug(f"Detected dynamic pattern: {path}")
         return path
 
@@ -264,6 +273,15 @@ 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
+            if "path" in self.__dict__:
+                del self.__dict__["path"]  # invalidate the cached property
+
+            if self._original_path is not None and self.path != self._original_path:
+                file_rename_required = True
+
         if self.path:
             if self.exists and self._frozen:
                 raise dataclasses.FrozenInstanceError(
@@ -279,6 +297,9 @@ 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