Fix behaviour of set_var_default() when setting a variable after test init

Author: vkarak

reframe/core/pipeline.py

@@ -1369,7 +1369,7 @@ def set_var_default(self, name, value):
         if name not in var_space:
             raise ValueError(f'no such variable: {name!r}')
 
-        if not var_space[name].is_defined():
+        if not hasattr(self, name):
             setattr(self, name, value)
 
     @loggable

unittests/test_pipeline.py

@@ -1980,18 +1980,21 @@ def test_set_var_default():
     class _X(rfm.RunOnlyRegressionTest):
         foo = variable(int, value=10)
         bar = variable(int)
+        zoo = variable(int)
 
         @run_after('init')
         def set_defaults(self):
             self.set_var_default('foo', 100)
             self.set_var_default('bar', 100)
-
+            self.zoo = 1
+            self.set_var_default('zoo', 100)
             with pytest.raises(ValueError):
                 self.set_var_default('foobar', 10)
 
     x = _X()
     assert x.foo == 10
     assert x.bar == 100
+    assert x.zoo == 1
 
 
 def test_hashcode():