Warn that `ipython_extension_dir` is Pending Deprecation.

docs/source/whatsnew/pr/pending-deprecation-ipython-extension.rst

@@ -0,0 +1,5 b''
+Loading extensions from ``ipython_extension_dir`` print a warning that this location is pending
+deprecation. This should only affect users still having extensions installed with ``%install_ext``
+which has been deprecated since IPython 4.0, and removed in 5.0. extensions still present in
+``ipython_extension_dir`` may shadow more recently installed versions using pip. It is thus
+recommended to clean ``ipython_extension_dir`` of any extension now available as a package.

IPython/core/extensions.py

@@ -1,170 +1,196 b''
 # encoding: utf-8
 """A class for managing IPython extensions."""
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 import os
+import os.path
+import warnings
+import textwrap
 from shutil import copyfile
 import sys
 from importlib import import_module
 
 from traitlets.config.configurable import Configurable
 from IPython.utils.path import ensure_dir_exists
 from traitlets import Instance
 
 try:
     from importlib import reload
 except ImportError :
     ## deprecated since 3.4
     from imp import reload
 
 #-----------------------------------------------------------------------------
 # Main class
 #-----------------------------------------------------------------------------
 
 class ExtensionManager(Configurable):
     """A class to manage IPython extensions.
 
     An IPython extension is an importable Python module that has
     a function with the signature::
 
         def load_ipython_extension(ipython):
             # Do things with ipython
 
     This function is called after your extension is imported and the
     currently active :class:`InteractiveShell` instance is passed as
     the only argument.  You can do anything you want with IPython at
     that point, including defining new magic and aliases, adding new
     components, etc.
     
     You can also optionally define an :func:`unload_ipython_extension(ipython)`
     function, which will be called if the user unloads or reloads the extension.
     The extension manager will only call :func:`load_ipython_extension` again
     if the extension is reloaded.
 
     You can put your extension modules anywhere you want, as long as
     they can be imported by Python's standard import mechanism.  However,
     to make it easy to write extensions, you can also put your extensions
     in ``os.path.join(self.ipython_dir, 'extensions')``.  This directory
     is added to ``sys.path`` automatically.
     """
 
     shell = Instance('IPython.core.interactiveshell.InteractiveShellABC', allow_none=True)
 
     def __init__(self, shell=None, **kwargs):
         super(ExtensionManager, self).__init__(shell=shell, **kwargs)
         self.shell.observe(
             self._on_ipython_dir_changed, names=('ipython_dir',)
         )
         self.loaded = set()
 
     @property
     def ipython_extension_dir(self):
         return os.path.join(self.shell.ipython_dir, u'extensions')
 
     def _on_ipython_dir_changed(self, change):
         ensure_dir_exists(self.ipython_extension_dir)
 
     def load_extension(self, module_str):
         """Load an IPython extension by its module name.
 
         Returns the string "already loaded" if the extension is already loaded,
         "no load function" if the module doesn't have a load_ipython_extension
         function, or None if it succeeded.
         """
         if module_str in self.loaded:
             return "already loaded"
-        
+
         from IPython.utils.syspathcontext import prepended_to_syspath
-        
+
         with self.shell.builtin_trap:
             if module_str not in sys.modules:
                 with prepended_to_syspath(self.ipython_extension_dir):
-                    import_module(module_str)
+                    mod = import_module(module_str)
+                    if mod.__file__.startswith(self.ipython_extension_dir):
+                        print(textwrap.dedent(
+                        """
+                        Warning, you are attempting to load and IPython extensions from legacy
+                        location.
+                            
+                        IPythonhas been requested to load extension `{ext}` which has been found in
+                        `ipython_extension_dir` (`{dir}`).
+
+                        It is likely you previously installed an extension using the `%install_ext`
+                        mechanism which has been deprecated since IPython 4.0. Loading extensions
+                        from the above directory is still supported but will be deprecated in a
+                        future version of IPython.
+
+                        Extensions should now be installed and managed as Python packages. We
+                        recommend you update your extensions accordingly.
+
+                        Old extensions files present in `ipython_extension_dir` may cause newly
+                        installed extensions to not be recognized. Thus you may need to clean
+                        the content of above mentioned directory.
+                        """.format(dir=self.ipython_extension_dir, ext=module_str)))
             mod = sys.modules[module_str]
             if self._call_load_ipython_extension(mod):
                 self.loaded.add(module_str)
             else:
                 return "no load function"
 
     def unload_extension(self, module_str):
         """Unload an IPython extension by its module name.
 
         This function looks up the extension's name in ``sys.modules`` and
         simply calls ``mod.unload_ipython_extension(self)``.
         
         Returns the string "no unload function" if the extension doesn't define
         a function to unload itself, "not loaded" if the extension isn't loaded,
         otherwise None.
         """
         if module_str not in self.loaded:
             return "not loaded"
         
         if module_str in sys.modules:
             mod = sys.modules[module_str]
             if self._call_unload_ipython_extension(mod):
                 self.loaded.discard(module_str)
             else:
                 return "no unload function"
 
     def reload_extension(self, module_str):
         """Reload an IPython extension by calling reload.
 
         If the module has not been loaded before,
         :meth:`InteractiveShell.load_extension` is called. Otherwise
         :func:`reload` is called and then the :func:`load_ipython_extension`
         function of the module, if it exists is called.
         """
         from IPython.utils.syspathcontext import prepended_to_syspath
 
         if (module_str in self.loaded) and (module_str in sys.modules):
             self.unload_extension(module_str)
             mod = sys.modules[module_str]
             with prepended_to_syspath(self.ipython_extension_dir):
                 reload(mod)
             if self._call_load_ipython_extension(mod):
                 self.loaded.add(module_str)
         else:
             self.load_extension(module_str)
 
     def _call_load_ipython_extension(self, mod):
         if hasattr(mod, 'load_ipython_extension'):
             mod.load_ipython_extension(self.shell)
             return True
 
     def _call_unload_ipython_extension(self, mod):
         if hasattr(mod, 'unload_ipython_extension'):
             mod.unload_ipython_extension(self.shell)
             return True
 
     def install_extension(self, url, filename=None):
         """Download and install an IPython extension. 
 
         If filename is given, the file will be so named (inside the extension
         directory). Otherwise, the name from the URL will be used. The file must
         have a .py or .zip extension; otherwise, a ValueError will be raised.
 
         Returns the full path to the installed file.
         """
         # Ensure the extension directory exists
         ensure_dir_exists(self.ipython_extension_dir)
 
         if os.path.isfile(url):
             src_filename = os.path.basename(url)
             copy = copyfile
         else:
             # Deferred imports
             from urllib.parse import urlparse
             from urllib.request import urlretrieve
             src_filename = urlparse(url).path.split('/')[-1]
             copy = urlretrieve
 
         if filename is None:
             filename = src_filename
         if os.path.splitext(filename)[1] not in ('.py', '.zip'):
             raise ValueError("The file must have a .py or .zip extension", filename)
 
         filename = os.path.join(self.ipython_extension_dir, filename)
         copy(url, filename)
         return filename
+
+