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: