Return a disabler when an unknown method is called on a disabler object

mesonbuild/interpreterbase.py

@@ -803,8 +803,11 @@ The result of this is undefined and will become a hard error in a future Meson r
         (args, kwargs) = self.reduce_arguments(args)
         # Special case. This is the only thing you can do with a disabler
         # object. Every other use immediately returns the disabler object.
-        if isinstance(obj, Disabler) and method_name == 'found':
+        if isinstance(obj, Disabler):
+            if method_name == 'found':
                 return False
+            else:
+                return Disabler()
         if is_disabled(args, kwargs):
             return Disabler()
         if method_name == 'extract_objects':

test cases/common/163 disabler/meson.build

@@ -2,6 +2,9 @@ project('dolphin option', 'c')
 
 d = disabler()
 
+full_path = d.full_path()
+assert(is_disabler(full_path), 'Method call is not a disabler')
+
 d2 = dependency(d)
 d3 = (d == d2)
 d4 = d + 0