Make sure that a goto on stubs even without the implementation is possible

jedi/inference/gradual/utils.py

@@ -21,8 +21,6 @@ def load_proper_stub_module(inference_state, file_io, import_names, module_node)
 
     if import_names is not None:
         actual_value_set = inference_state.import_module(import_names, prefer_stubs=False)
-        if not actual_value_set:
-            return None
 
         stub = create_stub_module(
             inference_state, actual_value_set, module_node, file_io, import_names

test/test_inference/test_gradual/test_conversion.py

@@ -1,5 +1,7 @@
-from os.path import join
+import os
 
+from test.helpers import root_dir
+from jedi.api.project import Project
 from jedi.inference.gradual.conversion import convert_names
 
 
@@ -21,3 +23,18 @@ def test_sqlite3_conversion(Script):
     assert d.full_name == 'sqlite3.Connection'
     v, = d._name.infer()
     assert v.is_compiled()
+
+
+def test_conversion_of_stub_only(Script):
+    project = Project(os.path.join(root_dir, 'test', 'completion', 'stub_folder'))
+    code = 'import stub_only; stub_only.in_stub_only'
+    d1, = Script(code, _project=project).goto_assignments()
+    assert d1.is_stub()
+
+    script = Script(path=d1.module_path, line=d1.line, column=d1.column, _project=project)
+    d2, = script.goto_assignments()
+    assert d2.is_stub()
+    assert d2.module_path == d1.module_path
+    assert d2.line == d1.line
+    assert d2.column == d1.column
+    assert d2.name == 'in_stub_only'