Avoid modifying mutable default value

IPython/extensions/autoreload.py

@@ -1,530 +1,532 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, bar``
 
     Import modules 'foo', 'bar' and mark them 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.
 """
 
 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
 from importlib import import_module
 from importlib.util import source_from_cache
 from imp import reload
 
 #------------------------------------------------------------------------------
 # Autoreload functionality
 #------------------------------------------------------------------------------
 
 class ModuleReloader(object):
     enabled = False
     """Whether this reloader is enabled"""
 
     check_all = True
     """Autoreload all modules, not just those listed in 'modules'"""
 
     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(module_name)
         top_name = module_name.split('.')[0]
         top_module = sys.modules[top_name]
         return top_module, top_name
 
     def filename_and_mtime(self, module):
         if not hasattr(module, '__file__') or module.__file__ is None:
             return None, None
 
         if getattr(module, '__name__', None) in [None, '__mp_main__', '__main__']:
             # we cannot reload(__main__) or reload(__mp_main__)
             return None, None
 
         filename = module.__file__
         path, ext = os.path.splitext(filename)
 
         if ext.lower() == '.py':
             py_filename = filename
         else:
             try:
                 py_filename = 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
 
             py_filename, pymtime = self.filename_and_mtime(m)
             if py_filename is None:
                 continue
 
             try:
                 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
 
             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(10)), file=sys.stderr)
                     self.failed[py_filename] = pymtime
 
 #------------------------------------------------------------------------------
 # superreload
 #------------------------------------------------------------------------------
 
 
 func_attrs = ['__code__', '__defaults__', '__doc__',
               '__closure__', '__globals__', '__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, and add new methods, if any"""
     for key in list(old.__dict__.keys()):
         old_obj = getattr(old, key)
         try:
             new_obj = getattr(new, key)
             if old_obj == new_obj:
                 continue
         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
 
     for key in list(new.__dict__.keys()):
         if key not in list(old.__dict__.keys()):
             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),
 ]
 UPDATE_RULES.extend([(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={}):
+def superreload(module, reload=reload, old_objects=None):
     """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
 
     """
+    if old_objects is None:
+        old_objects = {}
 
     # 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:
             pass
 
     # 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, bar
         Import modules 'foo', 'bar' and mark them 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:
             for _module in ([_.strip() for _ in modname.split(',')]):
                 top_module, top_name = self._reloader.aimport_module(_module)
 
                 # 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.events.register('post_execute', auto_reload.post_execute_hook)