Fix regression introduced by #1186 and add tests (#1204)

This closes #1200

Author: DanielNoord

astroid/nodes/scoped_nodes.py

@@ -752,7 +752,7 @@ def relative_to_absolute_name(self, modname, level):
         if package_name:
             if not modname:
                 return package_name
-            return f"{package_name}.{modname.split('.')[0]}"
+            return f"{package_name}.{modname}"
         return modname
 
     def wildcard_import_names(self):

tests/testdata/python3/data/beyond_top_level_two/__init__.py

@@ -0,0 +1,7 @@
+# pylint: disable=missing-docstring
+
+from .level1.beyond_top_level_two import func
+
+
+def do_something(var, some_other_var):  # error
+    func(var, some_other_var)

tests/testdata/python3/data/beyond_top_level_two/a.py

@@ -0,0 +1,2 @@
+def func(var):
+    pass

tests/testdata/python3/data/beyond_top_level_two/level1/__init__.py

@@ -0,0 +1,2 @@
+def func(var, some_other_var):
+    pass

tests/testdata/python3/data/beyond_top_level_two/level1/beyond_top_level_two.py

@@ -6540,5 +6540,11 @@ def test_namespace_package() -> None:
     resources.build_file("data/beyond_top_level/import_package.py")
 
 
+def test_namespace_package_same_name() -> None:
+    """check that a file using namespace packages and relative imports
+    with similar names is parseable"""
+    resources.build_file("data/beyond_top_level_two/a.py")
+
+
 if __name__ == "__main__":
     unittest.main()