Fixed #101 : Implement PLURIAL

Fixed #103 : Implement PlurialNodeParser
Fixed #104 : Implement dynamic concept
Fixed #107 : PrepareEvalxxxEvaluator: context hints are lost on a second evaluation

tests/core/test_SheerkaPluralManager.py

@@ -0,0 +1,76 @@
+from core.builtin_concepts_ids import BuiltinConcepts
+from core.global_symbols import NotFound
+from tests.TestUsingMemoryBasedSheerka import TestUsingMemoryBasedSheerka
+
+
+class TestSheerkaPluralManager(TestUsingMemoryBasedSheerka):
+    def test_i_can_set_plural(self):
+        sheerka, context, man, men = self.init_concepts("man", "men")
+
+        men_instance = sheerka.new("men")
+        res = sheerka.set_plural(context, men_instance, man)
+
+        assert res.status
+        assert men_instance.get_prop(BuiltinConcepts.PLURAL) == man
+        assert sheerka.is_plural(men_instance)
+        assert sheerka.is_plural(men_instance, man)
+
+        # global truth is not set
+        another_instance = sheerka.new("men")
+        assert another_instance.get_prop(BuiltinConcepts.PLURAL) is None
+
+    def test_i_can_set_plural_when_global_truth_is_set(self):
+        sheerka, context, man, men = self.init_concepts("man", "men", global_truth=True)
+
+        assert sheerka.known_plural(man) == NotFound
+
+        res = sheerka.set_plural(context, men, man)
+
+        assert res.status
+        assert sheerka.is_plural(men)
+
+        another_instance = sheerka.new("men")
+        assert sheerka.is_plural(another_instance)
+        assert sheerka.known_plural(man) == men.id
+
+    def test_i_cannot_set_plural_twice(self):
+        sheerka, context, man, men = self.init_concepts("man", "men")
+        men_instance = sheerka.new("men")
+        sheerka.set_plural(context, men_instance, man)
+
+        res = sheerka.set_plural(context, men_instance, man)
+
+        assert not res.status
+        assert sheerka.isinstance(res.body, BuiltinConcepts.PROPERTY_ALREADY_DEFINED)
+        assert res.body.concept == men_instance
+        assert res.body.property_name == BuiltinConcepts.PLURAL
+        assert res.body.property_value == man
+
+    def test_i_cannot_set_plural_twice_when_global_truth(self):
+        sheerka, context, man, men = self.init_concepts("man", "men", global_truth=True)
+        sheerka.set_plural(context, men, man)
+
+        another_instance = sheerka.new("men")
+        res = sheerka.set_plural(context, another_instance, man)
+
+        assert not res.status
+        assert sheerka.isinstance(res.body, BuiltinConcepts.PROPERTY_ALREADY_DEFINED)
+        assert res.body.concept == another_instance
+        assert res.body.property_name == BuiltinConcepts.PLURAL
+        assert res.body.property_value == man
+
+    def test_i_can_set_plural_twice_when_global_truth_is_true_the_second_time(self):
+        sheerka, context, man, men = self.init_concepts("man", "men")
+        global_truth_context = self.get_context(sheerka, global_truth=True)
+
+        men_instance = sheerka.new("men")
+        sheerka.set_plural(context, men_instance, man)
+
+        # set it again with global_truth = True
+        res = sheerka.set_plural(global_truth_context, men_instance, man)
+
+        assert res.status
+        assert men_instance.get_prop(BuiltinConcepts.PLURAL) == man
+
+        # and it's now true for all newly created context
+        assert sheerka.is_plural(sheerka.new("men"), man)