Store timestamps for modules to autoreload

Closes gh-4127

At present, autoreload compares the timestamps on .py and .pyc files.
However, this can fail in a couple of ways (see gh-4127). With this
change, it caches the mtime of the .py file when we loaded it.

Some extra complexity is needed to store the mtime as soon as possible -
we scan sys.modules when autoreload is loaded, and register a
post_execute hook to check for newly imported modules after each cell.

IPython/extensions/autoreload.py

@@ -1,505 +1,536 b''
 """IPython extension to reload modules before executing user code.
 
 ``autoreload`` reloads modules automatically before entering the execution of
 code typed at the IPython prompt.
 
 This makes for example the following workflow possible:
 
 .. sourcecode:: ipython
 
    In [1]: %load_ext autoreload
 
    In [2]: %autoreload 2
 
    In [3]: from foo import some_function
 
    In [4]: some_function()
    Out[4]: 42
 
    In [5]: # open foo.py in an editor and change some_function to return 43
 
    In [6]: some_function()
    Out[6]: 43
 
 The module was reloaded without reloading it explicitly, and the object
 imported with ``from foo import ...`` was also updated.
 
 Usage
 =====
 
 The following magic commands are provided:
 
 ``%autoreload``
 
     Reload all modules (except those excluded by ``%aimport``)
     automatically now.
 
 ``%autoreload 0``
 
     Disable automatic reloading.
 
 ``%autoreload 1``
 
     Reload all modules imported with ``%aimport`` every time before
     executing the Python code typed.
 
 ``%autoreload 2``
 
     Reload all modules (except those excluded by ``%aimport``) every
     time before executing the Python code typed.
 
 ``%aimport``
 
     List modules which are to be automatically imported or not to be imported.
 
 ``%aimport foo``
 
     Import module 'foo' and mark it to be autoreloaded for ``%autoreload 1``
 
 ``%aimport -foo``
 
     Mark module 'foo' to not be autoreloaded.
 
 Caveats
 =======
 
 Reloading Python modules in a reliable way is in general difficult,
 and unexpected things may occur. ``%autoreload`` tries to work around
 common pitfalls by replacing function code objects and parts of
 classes previously in the module with new versions. This makes the
 following things to work:
 
 - Functions and classes imported via 'from xxx import foo' are upgraded
   to new versions when 'xxx' is reloaded.
 
 - Methods and properties of classes are upgraded on reload, so that
   calling 'c.foo()' on an object 'c' created before the reload causes
   the new code for 'foo' to be executed.
 
 Some of the known remaining caveats are:
 
 - Replacing code objects does not always succeed: changing a @property
   in a class to an ordinary method or a method to a member variable
   can cause problems (but in old objects only).
 
 - Functions that are removed (eg. via monkey-patching) from a module
   before it is reloaded are not upgraded.
 
 - C extension modules cannot be reloaded, and so cannot be autoreloaded.
 """
 from __future__ import print_function
 
 skip_doctest = True
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2000 Thomas Heller
 #  Copyright (C) 2008 Pauli Virtanen <[e-mail]>
 #  Copyright (C) 2012  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-----------------------------------------------------------------------------
 #
 # This IPython module is written by Pauli Virtanen, based on the autoreload
 # code by Thomas Heller.
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 import os
 import sys
 import traceback
 import types
 import weakref
 
 try:
     # Reload is not defined by default in Python3.
     reload
 except NameError:
     from imp import reload
 
 from IPython.utils import openpy
 from IPython.utils.py3compat import PY3
 
 #------------------------------------------------------------------------------
 # Autoreload functionality
 #------------------------------------------------------------------------------
 
 class ModuleReloader(object):
     enabled = False
     """Whether this reloader is enabled"""
 
-    failed = {}
-    """Modules that failed to reload: {module: mtime-on-failed-reload, ...}"""
-
-    modules = {}
-    """Modules specially marked as autoreloadable."""
-
-    skip_modules = {}
-    """Modules specially marked as not autoreloadable."""
-
     check_all = True
     """Autoreload all modules, not just those listed in 'modules'"""
 
-    old_objects = {}
-    """(module-name, name) -> weakref, for replacing old code objects"""
+    def __init__(self):
+        # Modules that failed to reload: {module: mtime-on-failed-reload, ...}
+        self.failed = {}
+        # Modules specially marked as autoreloadable.
+        self.modules = {}
+        # Modules specially marked as not autoreloadable.
+        self.skip_modules = {}
+        # (module-name, name) -> weakref, for replacing old code objects
+        self.old_objects = {}
+        # Module modification timestamps
+        self.modules_mtimes = {}
+
+        # Cache module modification times
+        self.check(check_all=True, do_reload=False)
 
     def mark_module_skipped(self, module_name):
         """Skip reloading the named module in the future"""
         try:
             del self.modules[module_name]
         except KeyError:
             pass
         self.skip_modules[module_name] = True
 
     def mark_module_reloadable(self, module_name):
         """Reload the named module in the future (if it is imported)"""
         try:
             del self.skip_modules[module_name]
         except KeyError:
             pass
         self.modules[module_name] = True
 
     def aimport_module(self, module_name):
         """Import a module, and mark it reloadable
 
         Returns
         -------
         top_module : module
             The imported module if it is top-level, or the top-level
         top_name : module
             Name of top_module
 
         """
         self.mark_module_reloadable(module_name)
 
         __import__(module_name)
         top_name = module_name.split('.')[0]
         top_module = sys.modules[top_name]
         return top_module, top_name
 
-    def check(self, check_all=False):
+    def filename_and_mtime(self, module):
+        if not hasattr(module, '__file__'):
+            return None, None
+
+        if module.__name__ == '__main__':
+            # we cannot reload(__main__)
+            return None, None
+
+        filename = module.__file__
+        path, ext = os.path.splitext(filename)
+
+        if ext.lower() == '.py':
+            py_filename = filename
+        else:
+            try:
+                py_filename = openpy.source_from_cache(filename)
+            except ValueError:
+                return None, None
+
+        try:
+            pymtime = os.stat(py_filename).st_mtime
+        except OSError:
+            return None, None
+
+        return py_filename, pymtime
+
+    def check(self, check_all=False, do_reload=True):
         """Check whether some modules need to be reloaded."""
 
         if not self.enabled and not check_all:
             return
 
         if check_all or self.check_all:
             modules = list(sys.modules.keys())
         else:
             modules = list(self.modules.keys())
 
         for modname in modules:
             m = sys.modules.get(modname, None)
 
             if modname in self.skip_modules:
                 continue
 
-            if not hasattr(m, '__file__'):
+            py_filename, pymtime = self.filename_and_mtime(m)
+            if py_filename is None:
                 continue
 
-            if m.__name__ == '__main__':
-                # we cannot reload(__main__)
-                continue
-
-            filename = m.__file__
-            path, ext = os.path.splitext(filename)
-
-            if ext.lower() == '.py':
-                pyc_filename = openpy.cache_from_source(filename)
-                py_filename = filename
-            else:
-                pyc_filename = filename
-                try:
-                    py_filename = openpy.source_from_cache(filename)
-                except ValueError:
-                    continue
-
             try:
-                pymtime = os.stat(py_filename).st_mtime
-                if pymtime <= os.stat(pyc_filename).st_mtime:
+                if pymtime <= self.modules_mtimes[modname]:
                     continue
+            except KeyError:
+                self.modules_mtimes[modname] = pymtime
+                continue
+            else:
                 if self.failed.get(py_filename, None) == pymtime:
                     continue
-            except OSError:
-                continue
 
-            try:
-                superreload(m, reload, self.old_objects)
-                if py_filename in self.failed:
-                    del self.failed[py_filename]
-            except:
-                print("[autoreload of %s failed: %s]" % (
-                        modname, traceback.format_exc(1)), file=sys.stderr)
-                self.failed[py_filename] = pymtime
+            self.modules_mtimes[modname] = pymtime
+
+            # If we've reached this point, we should try to reload the module
+            if do_reload:
+                try:
+                    superreload(m, reload, self.old_objects)
+                    if py_filename in self.failed:
+                        del self.failed[py_filename]
+                except:
+                    print("[autoreload of %s failed: %s]" % (
+                            modname, traceback.format_exc(1)), file=sys.stderr)
+                    self.failed[py_filename] = pymtime
 
 #------------------------------------------------------------------------------
 # superreload
 #------------------------------------------------------------------------------
 
 if PY3:
     func_attrs = ['__code__', '__defaults__', '__doc__',
                   '__closure__', '__globals__', '__dict__']
 else:
     func_attrs = ['func_code', 'func_defaults', 'func_doc',
                   'func_closure', 'func_globals', 'func_dict']
 
 
 def update_function(old, new):
     """Upgrade the code object of a function"""
     for name in func_attrs:
         try:
             setattr(old, name, getattr(new, name))
         except (AttributeError, TypeError):
             pass
 
 
 def update_class(old, new):
     """Replace stuff in the __dict__ of a class, and upgrade
     method code objects"""
     for key in list(old.__dict__.keys()):
         old_obj = getattr(old, key)
 
         try:
             new_obj = getattr(new, key)
         except AttributeError:
             # obsolete attribute: remove it
             try:
                 delattr(old, key)
             except (AttributeError, TypeError):
                 pass
             continue
 
         if update_generic(old_obj, new_obj): continue
 
         try:
             setattr(old, key, getattr(new, key))
         except (AttributeError, TypeError):
             pass # skip non-writable attributes
 
 
 def update_property(old, new):
     """Replace get/set/del functions of a property"""
     update_generic(old.fdel, new.fdel)
     update_generic(old.fget, new.fget)
     update_generic(old.fset, new.fset)
 
 
 def isinstance2(a, b, typ):
     return isinstance(a, typ) and isinstance(b, typ)
 
 
 UPDATE_RULES = [
     (lambda a, b: isinstance2(a, b, type),
      update_class),
     (lambda a, b: isinstance2(a, b, types.FunctionType),
      update_function),
     (lambda a, b: isinstance2(a, b, property),
      update_property),
 ]
 
 
 if PY3:
     UPDATE_RULES.extend([(lambda a, b: isinstance2(a, b, types.MethodType),
                           lambda a, b: update_function(a.__func__, b.__func__)),
                         ])
 else:
     UPDATE_RULES.extend([(lambda a, b: isinstance2(a, b, types.ClassType),
                           update_class),
                          (lambda a, b: isinstance2(a, b, types.MethodType),
                           lambda a, b: update_function(a.__func__, b.__func__)),
                         ])
 
 
 def update_generic(a, b):
     for type_check, update in UPDATE_RULES:
         if type_check(a, b):
             update(a, b)
             return True
     return False
 
 
 class StrongRef(object):
     def __init__(self, obj):
         self.obj = obj
     def __call__(self):
         return self.obj
 
 
 def superreload(module, reload=reload, old_objects={}):
     """Enhanced version of the builtin reload function.
 
     superreload remembers objects previously in the module, and
 
     - upgrades the class dictionary of every old class in the module
     - upgrades the code object of every old function and method
     - clears the module's namespace before reloading
 
     """
 
     # collect old objects in the module
     for name, obj in list(module.__dict__.items()):
         if not hasattr(obj, '__module__') or obj.__module__ != module.__name__:
             continue
         key = (module.__name__, name)
         try:
             old_objects.setdefault(key, []).append(weakref.ref(obj))
         except TypeError:
             # weakref doesn't work for all types;
             # create strong references for 'important' cases
             if not PY3 and isinstance(obj, types.ClassType):
                 old_objects.setdefault(key, []).append(StrongRef(obj))
 
     # reload module
     try:
         # clear namespace first from old cruft
         old_dict = module.__dict__.copy()
         old_name = module.__name__
         module.__dict__.clear()
         module.__dict__['__name__'] = old_name
         module.__dict__['__loader__'] = old_dict['__loader__']
     except (TypeError, AttributeError, KeyError):
         pass
 
     try:
         module = reload(module)
     except:
         # restore module dictionary on failed reload
         module.__dict__.update(old_dict)
         raise
 
     # iterate over all objects and update functions & classes
     for name, new_obj in list(module.__dict__.items()):
         key = (module.__name__, name)
         if key not in old_objects: continue
 
         new_refs = []
         for old_ref in old_objects[key]:
             old_obj = old_ref()
             if old_obj is None: continue
             new_refs.append(old_ref)
             update_generic(old_obj, new_obj)
 
         if new_refs:
             old_objects[key] = new_refs
         else:
             del old_objects[key]
 
     return module
 
 #------------------------------------------------------------------------------
 # IPython connectivity
 #------------------------------------------------------------------------------
 
 from IPython.core.magic import Magics, magics_class, line_magic
 
 @magics_class
 class AutoreloadMagics(Magics):
     def __init__(self, *a, **kw):
         super(AutoreloadMagics, self).__init__(*a, **kw)
         self._reloader = ModuleReloader()
         self._reloader.check_all = False
+        self.loaded_modules = set(sys.modules)
 
     @line_magic
     def autoreload(self, parameter_s=''):
         r"""%autoreload => Reload modules automatically
 
         %autoreload
         Reload all modules (except those excluded by %aimport) automatically
         now.
 
         %autoreload 0
         Disable automatic reloading.
 
         %autoreload 1
         Reload all modules imported with %aimport every time before executing
         the Python code typed.
 
         %autoreload 2
         Reload all modules (except those excluded by %aimport) every time
         before executing the Python code typed.
 
         Reloading Python modules in a reliable way is in general
         difficult, and unexpected things may occur. %autoreload tries to
         work around common pitfalls by replacing function code objects and
         parts of classes previously in the module with new versions. This
         makes the following things to work:
 
         - Functions and classes imported via 'from xxx import foo' are upgraded
           to new versions when 'xxx' is reloaded.
 
         - Methods and properties of classes are upgraded on reload, so that
           calling 'c.foo()' on an object 'c' created before the reload causes
           the new code for 'foo' to be executed.
 
         Some of the known remaining caveats are:
 
         - Replacing code objects does not always succeed: changing a @property
           in a class to an ordinary method or a method to a member variable
           can cause problems (but in old objects only).
 
         - Functions that are removed (eg. via monkey-patching) from a module
           before it is reloaded are not upgraded.
 
         - C extension modules cannot be reloaded, and so cannot be
           autoreloaded.
 
         """
         if parameter_s == '':
             self._reloader.check(True)
         elif parameter_s == '0':
             self._reloader.enabled = False
         elif parameter_s == '1':
             self._reloader.check_all = False
             self._reloader.enabled = True
         elif parameter_s == '2':
             self._reloader.check_all = True
             self._reloader.enabled = True
 
     @line_magic
     def aimport(self, parameter_s='', stream=None):
         """%aimport => Import modules for automatic reloading.
 
         %aimport
         List modules to automatically import and not to import.
 
         %aimport foo
         Import module 'foo' and mark it to be autoreloaded for %autoreload 1
 
         %aimport -foo
         Mark module 'foo' to not be autoreloaded for %autoreload 1
         """
         modname = parameter_s
         if not modname:
             to_reload = sorted(self._reloader.modules.keys())
             to_skip = sorted(self._reloader.skip_modules.keys())
             if stream is None:
                 stream = sys.stdout
             if self._reloader.check_all:
                 stream.write("Modules to reload:\nall-except-skipped\n")
             else:
                 stream.write("Modules to reload:\n%s\n" % ' '.join(to_reload))
             stream.write("\nModules to skip:\n%s\n" % ' '.join(to_skip))
         elif modname.startswith('-'):
             modname = modname[1:]
             self._reloader.mark_module_skipped(modname)
         else:
             top_module, top_name = self._reloader.aimport_module(modname)
 
             # Inject module to user namespace
             self.shell.push({top_name: top_module})
 
     def pre_run_cell(self):
         if self._reloader.enabled:
             try:
                 self._reloader.check()
             except:
                 pass
 
+    def post_execute_hook(self):
+        """Cache the modification times of any modules imported in this execution
+        """
+        newly_loaded_modules = set(sys.modules) - self.loaded_modules
+        for modname in newly_loaded_modules:
+            _, pymtime = self._reloader.filename_and_mtime(sys.modules[modname])
+            if pymtime is not None:
+                self._reloader.modules_mtimes[modname] = pymtime
+
+        self.loaded_modules.update(newly_loaded_modules)
+
 
 def load_ipython_extension(ip):
     """Load the extension in IPython."""
     auto_reload = AutoreloadMagics(ip)
     ip.register_magics(auto_reload)
     ip.events.register('pre_run_cell', auto_reload.pre_run_cell)
+    ip.register_post_execute(auto_reload.post_execute_hook)

IPython/extensions/tests/test_autoreload.py

@@ -1,321 +1,321 b''
 """Tests for autoreload extension.
 """
 #-----------------------------------------------------------------------------
 #  Copyright (c) 2012 IPython Development Team.
 #
 #  Distributed under the terms of the Modified BSD License.
 #
 #  The full license is in the file COPYING.txt, distributed with this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 import os
 import sys
 import tempfile
 import shutil
 import random
 import time
 
 import nose.tools as nt
 import IPython.testing.tools as tt
 
 from IPython.extensions.autoreload import AutoreloadMagics
 from IPython.core.events import EventManager, pre_run_cell
 from IPython.utils.py3compat import PY3
 
 if PY3:
     from io import StringIO
 else:
     from StringIO import StringIO
 
 #-----------------------------------------------------------------------------
 # Test fixture
 #-----------------------------------------------------------------------------
 
 noop = lambda *a, **kw: None
 
 class FakeShell(object):
 
     def __init__(self):
         self.ns = {}
         self.events = EventManager(self, {'pre_run_cell', pre_run_cell})
         self.auto_magics = AutoreloadMagics(shell=self)
         self.events.register('pre_run_cell', self.auto_magics.pre_run_cell)
 
     register_magics = set_hook = noop
 
     def run_code(self, code):
         self.events.trigger('pre_run_cell')
         exec(code, self.ns)
+        self.auto_magics.post_execute_hook()
 
     def push(self, items):
         self.ns.update(items)
 
     def magic_autoreload(self, parameter):
         self.auto_magics.autoreload(parameter)
 
     def magic_aimport(self, parameter, stream=None):
         self.auto_magics.aimport(parameter, stream=stream)
+        self.auto_magics.post_execute_hook()
 
 
 class Fixture(object):
     """Fixture for creating test module files"""
 
     test_dir = None
     old_sys_path = None
     filename_chars = "abcdefghijklmopqrstuvwxyz0123456789"
 
     def setUp(self):
         self.test_dir = tempfile.mkdtemp()
         self.old_sys_path = list(sys.path)
         sys.path.insert(0, self.test_dir)
         self.shell = FakeShell()
 
     def tearDown(self):
         shutil.rmtree(self.test_dir)
         sys.path = self.old_sys_path
 
         self.test_dir = None
         self.old_sys_path = None
         self.shell = None
 
     def get_module(self):
         module_name = "tmpmod_" + "".join(random.sample(self.filename_chars,20))
         if module_name in sys.modules:
             del sys.modules[module_name]
         file_name = os.path.join(self.test_dir, module_name + ".py")
         return module_name, file_name
 
     def write_file(self, filename, content):
         """
         Write a file, and force a timestamp difference of at least one second
 
         Notes
         -----
         Python's .pyc files record the timestamp of their compilation
         with a time resolution of one second.
 
         Therefore, we need to force a timestamp difference between .py
         and .pyc, without having the .py file be timestamped in the
         future, and without changing the timestamp of the .pyc file
         (because that is stored in the file).  The only reliable way
         to achieve this seems to be to sleep.
         """
 
         # Sleep one second + eps
         time.sleep(1.05)
 
         # Write
         f = open(filename, 'w')
         try:
             f.write(content)
         finally:
             f.close()
 
     def new_module(self, code):
         mod_name, mod_fn = self.get_module()
         f = open(mod_fn, 'w')
         try:
             f.write(code)
         finally:
             f.close()
         return mod_name, mod_fn
 
 #-----------------------------------------------------------------------------
 # Test automatic reloading
 #-----------------------------------------------------------------------------
 
 class TestAutoreload(Fixture):
     def _check_smoketest(self, use_aimport=True):
         """
         Functional test for the automatic reloader using either
         '%autoreload 1' or '%autoreload 2'
         """
 
         mod_name, mod_fn = self.new_module("""
 x = 9
 
 z = 123  # this item will be deleted
 
 def foo(y):
     return y + 3
 
 class Baz(object):
     def __init__(self, x):
         self.x = x
     def bar(self, y):
         return self.x + y
     @property
     def quux(self):
         return 42
     def zzz(self):
         '''This method will be deleted below'''
         return 99
 
 class Bar:    # old-style class: weakref doesn't work for it on Python < 2.7
     def foo(self):
         return 1
 """)
 
         #
         # Import module, and mark for reloading
         #
         if use_aimport:
             self.shell.magic_autoreload("1")
             self.shell.magic_aimport(mod_name)
             stream = StringIO()
             self.shell.magic_aimport("", stream=stream)
-            nt.assert_true(("Modules to reload:\n%s" % mod_name) in
-                           stream.getvalue())
+            nt.assert_in(("Modules to reload:\n%s" % mod_name), stream.getvalue())
 
-            nt.assert_raises(
-                ImportError,
-                self.shell.magic_aimport, "tmpmod_as318989e89ds")
+            with nt.assert_raises(ImportError):
+                self.shell.magic_aimport("tmpmod_as318989e89ds")
         else:
             self.shell.magic_autoreload("2")
             self.shell.run_code("import %s" % mod_name)
             stream = StringIO()
             self.shell.magic_aimport("", stream=stream)
             nt.assert_true("Modules to reload:\nall-except-skipped" in
                            stream.getvalue())
         nt.assert_in(mod_name, self.shell.ns)
 
         mod = sys.modules[mod_name]
 
         #
         # Test module contents
         #
         old_foo = mod.foo
         old_obj = mod.Baz(9)
         old_obj2 = mod.Bar()
 
         def check_module_contents():
             nt.assert_equal(mod.x, 9)
             nt.assert_equal(mod.z, 123)
 
             nt.assert_equal(old_foo(0), 3)
             nt.assert_equal(mod.foo(0), 3)
 
             obj = mod.Baz(9)
             nt.assert_equal(old_obj.bar(1), 10)
             nt.assert_equal(obj.bar(1), 10)
             nt.assert_equal(obj.quux, 42)
             nt.assert_equal(obj.zzz(), 99)
 
             obj2 = mod.Bar()
             nt.assert_equal(old_obj2.foo(), 1)
             nt.assert_equal(obj2.foo(), 1)
 
         check_module_contents()
 
         #
         # Simulate a failed reload: no reload should occur and exactly
         # one error message should be printed
         #
         self.write_file(mod_fn, """
 a syntax error
 """)
 
         with tt.AssertPrints(('[autoreload of %s failed:' % mod_name), channel='stderr'):
             self.shell.run_code("pass") # trigger reload
         with tt.AssertNotPrints(('[autoreload of %s failed:' % mod_name), channel='stderr'):
             self.shell.run_code("pass") # trigger another reload
         check_module_contents()
 
         #
         # Rewrite module (this time reload should succeed)
         #
         self.write_file(mod_fn, """
 x = 10
 
 def foo(y):
     return y + 4
 
 class Baz(object):
     def __init__(self, x):
         self.x = x
     def bar(self, y):
         return self.x + y + 1
     @property
     def quux(self):
         return 43
 
 class Bar:    # old-style class
     def foo(self):
         return 2
 """)
 
         def check_module_contents():
             nt.assert_equal(mod.x, 10)
             nt.assert_false(hasattr(mod, 'z'))
 
             nt.assert_equal(old_foo(0), 4) # superreload magic!
             nt.assert_equal(mod.foo(0), 4)
 
             obj = mod.Baz(9)
             nt.assert_equal(old_obj.bar(1), 11) # superreload magic!
             nt.assert_equal(obj.bar(1), 11)
 
             nt.assert_equal(old_obj.quux, 43)
             nt.assert_equal(obj.quux, 43)
 
             nt.assert_false(hasattr(old_obj, 'zzz'))
             nt.assert_false(hasattr(obj, 'zzz'))
 
             obj2 = mod.Bar()
             nt.assert_equal(old_obj2.foo(), 2)
             nt.assert_equal(obj2.foo(), 2)
 
         self.shell.run_code("pass") # trigger reload
         check_module_contents()
 
         #
         # Another failure case: deleted file (shouldn't reload)
         #
         os.unlink(mod_fn)
 
         self.shell.run_code("pass") # trigger reload
         check_module_contents()
 
         #
         # Disable autoreload and rewrite module: no reload should occur
         #
         if use_aimport:
             self.shell.magic_aimport("-" + mod_name)
             stream = StringIO()
             self.shell.magic_aimport("", stream=stream)
             nt.assert_true(("Modules to skip:\n%s" % mod_name) in
                            stream.getvalue())
 
             # This should succeed, although no such module exists
             self.shell.magic_aimport("-tmpmod_as318989e89ds")
         else:
             self.shell.magic_autoreload("0")
 
         self.write_file(mod_fn, """
 x = -99
 """)
 
         self.shell.run_code("pass") # trigger reload
         self.shell.run_code("pass")
         check_module_contents()
 
         #
         # Re-enable autoreload: reload should now occur
         #
         if use_aimport:
             self.shell.magic_aimport(mod_name)
         else:
             self.shell.magic_autoreload("")
 
         self.shell.run_code("pass") # trigger reload
         nt.assert_equal(mod.x, -99)
 
     def test_smoketest_aimport(self):
         self._check_smoketest(use_aimport=True)
 
     def test_smoketest_autoreload(self):
         self._check_smoketest(use_aimport=False)