os.path.sep should always have a clear value

CHANGELOG.rst

@@ -7,7 +7,7 @@ Changelog
 +++++++++++++++++++
 
 - Added file path completions, there's a **new ``Completion.type``** ``path``,
-  now.
+  now. Example: ``'/ho`` -> ``'/home/``
 - ``*args``/``**kwargs`` resolving. If possible Jedi replaces the parameters
   with the actual alternatives.
 - Better support for enums/dataclasses

jedi/evaluate/syntax_tree.py

@@ -27,6 +27,7 @@ from jedi.evaluate.cache import evaluator_method_cache
 from jedi.evaluate.gradual.stub_context import VersionInfo
 from jedi.evaluate.gradual import annotation
 from jedi.evaluate.context.decorator import Decoratee
+from jedi.plugins import plugin_manager
 
 
 def _limit_context_infers(func):
@@ -545,6 +546,7 @@ def _remove_statements(evaluator, context, stmt, name):
     return eval_expr_stmt(context, stmt, seek_name=name)
 
 
+@plugin_manager.decorate()
 def tree_name_to_contexts(evaluator, context, tree_name):
     context_set = NO_CONTEXTS
     module_node = context.get_root_context().tree_node

jedi/plugins/stdlib.py

@@ -789,3 +789,13 @@ class EnumInstance(LazyContextWrapper):
         ))
         for f in self._get_wrapped_context().get_filters():
             yield f
+
+
+def tree_name_to_contexts(func):
+    def wrapper(evaluator, context, tree_name):
+        if tree_name.value == 'sep' and context.is_module() and context.py__name__() == 'os.path':
+            return ContextSet({
+                compiled.create_simple_object(evaluator, os.path.sep),
+            })
+        return func(evaluator, context, tree_name)
+    return wrapper

test/test_api/test_completion.py

@@ -161,6 +161,7 @@ def test_keyword_completion(Script, code, has_keywords):
 
 f1 = join(root_dir, 'example.py')
 f2 = join(root_dir, 'test', 'example.py')
+os_path = 'from os.path import *\n'
 
 
 @pytest.mark.parametrize(
@@ -205,10 +206,9 @@ f2 = join(root_dir, 'test', 'example.py')
         ('example.py', '"test" + "', None, [s]),
 
         # __file__
-        (f1, 'from os.path import *\ndirname(__file__) + "%stest' % s, None, [s]),
-        (f2, 'from os.path import *\ndirname(__file__) + "%stest_ca' % s, None, ['che.py']),
-        (f2, 'from os.path import *\ndirname(abspath(__file__)) + "%stest_ca' % s,
-         None, ['che.py']),
+        (f1, os_path + 'dirname(__file__) + "%stest' % s, None, [s]),
+        (f2, os_path + 'dirname(__file__) + "%stest_ca' % s, None, ['che.py']),
+        (f2, os_path + 'dirname(abspath(__file__)) + sep + "test_ca', None, ['che.py']),
     ]
 )
 def test_file_path_completions(Script, file, code, column, expected):