Make AttributeDict additive

._read_only attribute is now a dict of name -> msgs

Overrides .update() method to use __setitem__ implementation

Includes updates to unit tests

Author: bormanjo

dash/_utils.py

@@ -137,23 +137,37 @@ def __getattr__(self, key):
         raise AttributeError(key)
 
     def set_read_only(self, names, msg="Attribute is read-only"):
-        object.__setattr__(self, "_read_only", names)
-        object.__setattr__(self, "_read_only_msg", msg)
+        """
+        Designate named attributes as read-only with the corresponding msg
+
+        Method is additive. Making additional calls to this method will update
+        existing messages and add to the current set of _read_only names.
+        """
+        new_read_only = {name: msg for name in names}
+        if getattr(self, "_read_only", False):
+            self._read_only.update(new_read_only)
+        else:
+            object.__setattr__(self, "_read_only", new_read_only)
 
     def finalize(self, msg="Object is final: No new keys may be added."):
         """Prevent any new keys being set."""
         object.__setattr__(self, "_final", msg)
 
     def __setitem__(self, key, val):
-        if key in self.__dict__.get("_read_only", []):
-            raise AttributeError(self._read_only_msg, key)
+        if key in self.__dict__.get("_read_only", {}):
+            raise AttributeError(self._read_only[key], key)
 
         final_msg = self.__dict__.get("_final")
         if final_msg and key not in self:
             raise AttributeError(final_msg, key)
 
         return super().__setitem__(key, val)
 
+    def update(self, other):
+        # Overrides dict.update() to use __setitem__ above
+        for k, v in other.items():
+            self[k] = v
+
     # pylint: disable=inconsistent-return-statements
     def first(self, *names):
         for name in names:

tests/unit/dash/test_utils.py

@@ -24,12 +24,13 @@ def test_ddut001_attribute_dict():
     assert a.k == 2
     assert a["k"] == 2
 
-    a.set_read_only(["k", "q"], "boo")
+    a.set_read_only(["k"], "boo")
 
     with pytest.raises(AttributeError) as err:
         a.k = 3
     assert err.value.args == ("boo", "k")
     assert a.k == 2
+    assert a._read_only == {"k": "boo"}
 
     with pytest.raises(AttributeError) as err:
         a["k"] = 3
@@ -38,13 +39,11 @@ def test_ddut001_attribute_dict():
 
     a.set_read_only(["q"])
 
-    a.k = 3
-    assert a.k == 3
-
     with pytest.raises(AttributeError) as err:
         a.q = 3
     assert err.value.args == ("Attribute is read-only", "q")
     assert "q" not in a
+    assert a._read_only == {"k": "boo", "q": "Attribute is read-only"}
 
     a.finalize("nope")