The docstring of import completions was wrong.

This is fixed now. However, since this might massively decrease performance,
it's not enabled by default. You can enable it with `docstring(fast=False)`
(see test changes), but I wouldn't recommend it at this point.

Fixes #656.

jedi/evaluate/imports.py

@@ -355,7 +355,11 @@ class Importer(object):
         return set([module])
 
     def _generate_name(self, name):
-        return helpers.FakeName(name, parent=self.module)
+        # Create a pseudo import to be able to follow them.
+        name = helpers.FakeName(name)
+        imp = helpers.FakeImport(name, parent=self.module)
+        name.parent = imp
+        return name
 
     def _get_module_names(self, search_path=None):
         """

test/test_evaluate/test_imports.py

@@ -77,3 +77,15 @@ def test_cache_works_with_sys_path_param(tmpdir):
 
     assert 'bar' in [c.name for c in bar_completions]
     assert 'foo' not in [c.name for c in bar_completions]
+
+
+def test_import_completion_docstring():
+    import abc
+    s = jedi.Script('"""test"""\nimport ab')
+    completions = s.completions()
+    assert len(completions) == 1
+    assert completions[0].docstring(fast=False) == abc.__doc__
+
+    # However for performance reasons not all modules are loaded and the
+    # docstring is empty in this case.
+    assert completions[0].docstring() == ''