Implement is_stub and goto_stubs for the API

jedi/api/classes.py

@@ -301,6 +301,18 @@ class BaseDefinition(object):
 
         return '.'.join(path if path[0] else path[1:])
 
+    def is_stub(self):
+        return all(c.is_stub() for c in self._name.infer())
+
+    def goto_stubs(self):
+        if self.is_stub():
+            return [self]
+
+        return [
+            Definition(self._evaluator, d.stub_context.name)
+            for d in self._name.infer() if d.stub_context is not None
+        ]
+
     def goto_assignments(self):
         if self._name.tree_name is None:
             return self

jedi/evaluate/base_context.py

@@ -102,6 +102,10 @@ class Context(HelperContextMixin, BaseContext):
     To be defined by subclasses.
     """
     tree_node = None
+    stub_context = None
+
+    def is_stub(self):
+        return False
 
     @property
     def api_type(self):

jedi/evaluate/gradual/stub_context.py

@@ -87,6 +87,9 @@ class StubMethodContext(StubFunctionContext):
 class _StubOnlyContextMixin(object):
     _add_non_stubs_in_filter = False
 
+    def is_stub(self):
+        return True
+
     def _get_stub_only_filters(self, **filter_kwargs):
         return [StubOnlyFilter(
             self.evaluator,
@@ -155,6 +158,9 @@ class _CompiledStubContext(ContextWrapper):
         super(_CompiledStubContext, self).__init__(stub_context)
         self._compiled_context = compiled_context
 
+    def is_stub(self):
+        return True
+
     def py__doc__(self, include_call_signature=False):
         doc = self._compiled_context.py__doc__()
         if include_call_signature:

test/test_evaluate/test_gradual/test_typeshed.py

@@ -152,12 +152,34 @@ def test_type_var(Script):
     assert def_.description == 'TypeVar = object()'
 
 
-@pytest.mark.parametrize('code', ('import math', 'from math import cos'))
+@pytest.mark.parametrize(
-def test_math_is_stub(Script, code):
+    'code, full_name', (
+        ('import math', 'math'),
+        ('from math import cos', 'math.cos')
+    )
+)
+def test_math_is_stub(Script, code, full_name):
     s = Script(code)
     cos, = s.goto_definitions()
     wanted = os.path.join('typeshed', 'stdlib', '2and3', 'math.pyi')
     assert cos.module_path.endswith(wanted)
+    assert cos.is_stub() is True
+    assert cos.goto_stubs() == [cos]
+    assert cos.full_name == full_name
 
     cos, = s.goto_assignments()
     assert cos.module_path.endswith(wanted)
+    assert cos.goto_stubs() == [cos]
+    assert cos.is_stub() is True
+    assert cos.full_name == full_name
+
+
+def test_goto_stubs(Script):
+    s = Script('import os; os')
+    os_module, = s.goto_definitions()
+    assert os_module.full_name == 'os'
+    assert os_module.is_stub() is False
+    stub, = os_module.goto_stubs()
+    assert stub.is_stub() is True
+
+    os_module, = s.goto_assignments()