Be careful about marking facets modified

Make sure to only set the modified flag on a facet when setting a
value if it has no corresponding node in its origin or the value
differs. This prevents the engine from unnecessarily rewriting the
origin's backing file on startup or reload.

diff --git a/mudpy/misc.py b/mudpy/misc.py
index 2da1b40..a23b834 100644 (file)
--- a/mudpy/misc.py
+++ b/mudpy/misc.py
@@ -129,16 +129,25 @@ class Element:
             # updated data from files
             raise PermissionError("Altering elements in read-only files is "
                                   "disallowed")
+        # Coerce some values to appropriate data types
+        # TODO(fungi) Move these to a separate validation mechanism
         if facet in ["loglevel"]:
             value = int(value)
         elif facet in ["administrator"]:
             value = bool(value)
-        if not self.has_facet(facet) or not self.get(facet) == value:
-            node = ".".join((self.key, facet))
+
+        # The canonical node for this facet within its origin
+        node = ".".join((self.key, facet))
+
+        if node not in self.origin.data or self.origin.data[node] != value:
+            # Be careful to only update the origin's contents when required,
+            # since that affects whether the backing file gets written
             self.origin.data[node] = value
-            self.facethash[facet] = self.origin.data[node]
             self.origin.modified = True
 
+        # Make sure this facet is included in the element's facets
+        self.facethash[facet] = self.origin.data[node]
+
     def append(self, facet, value):
         """Append value to a list."""
         newlist = self.get(facet)