interpreterbase: Add disabler exception for get_variable method

Add an exception to the disabler check to allow objects with a `get_variable`
method to not always pick a disabler if their arguments contain one. This
mimics the behaviour already in place for calls to function, which has a set
of excepted functions.

Fixes #13717

mesonbuild/interpreterbase/interpreterbase.py

@@ -543,7 +543,7 @@ def method_call(self, node: mparser.MethodNode) -> T.Optional[InterpreterObject]
         method_name = node.name.value
         (h_args, h_kwargs) = self.reduce_arguments(node.args)
         (args, kwargs) = self._unholder_args(h_args, h_kwargs)
-        if is_disabled(args, kwargs):
+        if is_disabled(args, kwargs) and method_name != 'get_variable':
             return Disabler()
         if not isinstance(obj, InterpreterObject):
             raise InvalidArguments(f'{object_display_name} is not callable.')

test cases/common/280 subproject get_variable disabler/meson.build

@@ -0,0 +1,11 @@
+# https://github.com/mesonbuild/meson/issues/13717
+
+project('foo', 'c')
+
+bar_subproj = subproject('bar')
+bar_dep = bar_subproj.get_variable('bar_dep', disabler())
+
+if is_disabler(bar_dep)
+    error('bar_dep is a disabler')
+endif
+

test cases/common/280 subproject get_variable disabler/subprojects/bar/meson.build

@@ -0,0 +1,2 @@
+project('bar', 'c')
+bar_dep = declare_dependency()