Add custom logic for pickling dynamic imports.

Add test cases, special case Ellipsis and NotImplemented.
Use custom logic in lieu of imp.find_module to properly follow subimports. For example sklearn.tree was spuriously treated as a dynamic module.

cloudpickle/cloudpickle.py

@@ -44,6 +44,7 @@
 
 import operator
 import io
+import imp
 import pickle
 import struct
 import sys
@@ -134,8 +135,19 @@ def save_module(self, obj):
         """
         Save a module as an import
         """
+        mod_name = obj.__name__
+        # If module is successfully found then it is not a dynamically created module
+        try:
+            _find_module(mod_name)
+            is_dynamic = False
+        except ImportError:
+            is_dynamic = True
+
         self.modules.add(obj)
-        self.save_reduce(subimport, (obj.__name__,), obj=obj)
+        if is_dynamic:
+            self.save_reduce(dynamic_subimport, (obj.__name__, vars(obj)), obj=obj)
+        else:
+            self.save_reduce(subimport, (obj.__name__,), obj=obj)
     dispatch[types.ModuleType] = save_module
 
     def save_codeobject(self, obj):
@@ -313,7 +325,7 @@ def extract_func_data(self, func):
         return (code, f_globals, defaults, closure, dct, base_globals)
 
     def save_builtin_function(self, obj):
-        if obj.__module__ is "__builtin__":
+        if obj.__module__ == "__builtin__":
             return self.save_global(obj)
         return self.save_function(obj)
     dispatch[types.BuiltinFunctionType] = save_builtin_function
@@ -584,11 +596,20 @@ def save_file(self, obj):
         self.save(retval)
         self.memoize(obj)
 
+    def save_ellipsis(self, obj):
+        self.save_reduce(_gen_ellipsis, ())
+
+    def save_not_implemented(self, obj):
+        self.save_reduce(_gen_not_implemented, ())
+
     if PY3:
         dispatch[io.TextIOWrapper] = save_file
     else:
         dispatch[file] = save_file
 
+    dispatch[type(Ellipsis)] = save_ellipsis
+    dispatch[type(NotImplemented)] = save_not_implemented
+
     """Special functions for Add-on libraries"""
     def inject_addons(self):
         """Plug in system. Register additional pickling functions if modules already loaded"""
@@ -620,6 +641,12 @@ def subimport(name):
     return sys.modules[name]
 
 
+def dynamic_subimport(name, vars):
+    mod = imp.new_module(name)
+    mod.__dict__.update(vars)
+    sys.modules[name] = mod
+    return mod
+
 # restores function attributes
 def _restore_attr(obj, attr):
     for key, val in attr.items():
@@ -663,6 +690,11 @@ def _genpartial(func, args, kwds):
         kwds = {}
     return partial(func, *args, **kwds)
 
+def _gen_ellipsis():
+    return Ellipsis
+
+def _gen_not_implemented():
+    return NotImplemented
 
 def _fill_function(func, globals, defaults, dict):
     """ Fills in the rest of function data into the skeleton function object
@@ -698,6 +730,18 @@ def _make_skel_func(code, closures, base_globals = None):
                               None, None, closure)
 
 
+def _find_module(mod_name):
+    """
+    Iterate over each part instead of calling imp.find_module directly.
+    This function is able to find submodules (e.g. sickit.tree)
+    """
+    path = None
+    for part in mod_name.split('.'):
+        if path is not None:
+            path = [path]
+        file, path, description = imp.find_module(part, path)
+    return file, path, description
+
 """Constructors for 3rd party libraries
 Note: These can never be renamed due to client compatibility issues"""
 

tests/cloudpickle_test.py

@@ -1,10 +1,12 @@
 from __future__ import division
+import imp
 import unittest
 import pytest
 import pickle
 import sys
 import functools
 import platform
+import textwrap
 
 try:
     # try importing numpy and scipy. These are not hard dependencies and
@@ -252,6 +254,30 @@ def f(self, x):
             self.assertEqual(g.im_class.__name__, F.f.im_class.__name__)
         # self.assertEqual(g(F(), 1), 2)  # still fails
 
+    def test_module(self):
+        self.assertEqual(pickle, pickle_depickle(pickle))
+
+    def test_dynamic_module(self):
+        mod = imp.new_module('mod')
+        code = '''
+        x = 1
+        def f(y):
+            return x + y
+        '''
+        exec(textwrap.dedent(code), mod.__dict__)
+        mod2 = pickle_depickle(mod)
+        self.assertEqual(mod.x, mod2.x)
+        self.assertEqual(mod.f(5), mod2.f(5))
+
+        # Test dynamic modules when imported back are singletons
+        mod1, mod2 = pickle_depickle([mod, mod])
+        self.assertEqual(id(mod1), id(mod2))
+
+    def test_Ellipsis(self):
+        self.assertEqual(Ellipsis, pickle_depickle(Ellipsis))
+
+    def test_NotImplemented(self):
+        self.assertEqual(NotImplemented, pickle_depickle(NotImplemented))
 
 if __name__ == '__main__':
     unittest.main()