Add test_no_duplicate_modules

test/test_regression.py

@@ -537,5 +537,41 @@ def test_settings_module():
     assert cache.settings is settings
 
 
+def test_no_duplicate_modules():
+    """
+    Make sure that import hack works as expected.
+
+    Jedi does an import hack (see: jedi/__init__.py) to have submodules
+    with circular dependencies.  The modules in this circular dependency
+    "loop" must be imported by ``import <module>`` rather than normal
+    ``from jedi import <module>`` (or ``from . jedi ...``).  This test
+    make sure that this is satisfied.
+
+    See also:
+
+    - `#160 <https://github.com/davidhalter/jedi/issues/160>`_
+    - `#161 <https://github.com/davidhalter/jedi/issues/161>`_
+    """
+    import sys
+    jedipath = os.path.dirname(os.path.abspath(jedi.__file__))
+
+    def is_submodule(m):
+        try:
+            filepath = m.__file__
+        except AttributeError:
+            return False
+        return os.path.abspath(filepath).startswith(jedipath)
+
+    modules = list(filter(is_submodule, sys.modules.values()))
+    top_modules = [m for m in modules if not m.__name__.startswith('jedi.')]
+    for m in modules:
+        for tm in top_modules:
+            try:
+                imported = getattr(m, tm.__name__)
+            except AttributeError:
+                continue
+            assert imported is tm
+
+
 if __name__ == '__main__':
     unittest.main()