Extension manager refuses to load extension more than once

IPython/core/extensions.py

@@ -1,164 +1,178 b''
 # encoding: utf-8
 """A class for managing IPython extensions.
 
 Authors:
 
 * Brian Granger
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2010-2011  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.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 import os
 from shutil import copyfile
 import sys
 from urllib import urlretrieve
 from urlparse import urlparse
 
+from IPython.core.error import UsageError
 from IPython.config.configurable import Configurable
 from IPython.utils.traitlets import Instance
 
 #-----------------------------------------------------------------------------
 # 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.
-
-    The :func:`load_ipython_extension` will be called again is you
-    load or reload the extension again.  It is up to the extension
-    author to add code to manage that.
+    
+    You can also optionaly 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')
 
     def __init__(self, shell=None, config=None):
         super(ExtensionManager, self).__init__(shell=shell, config=config)
         self.shell.on_trait_change(
             self._on_ipython_dir_changed, 'ipython_dir'
         )
         self.loaded = set()
 
     def __del__(self):
         self.shell.on_trait_change(
             self._on_ipython_dir_changed, 'ipython_dir', remove=True
         )
 
     @property
     def ipython_extension_dir(self):
         return os.path.join(self.shell.ipython_dir, u'extensions')
 
     def _on_ipython_dir_changed(self):
         if not os.path.isdir(self.ipython_extension_dir):
             os.makedirs(self.ipython_extension_dir, mode = 0o777)
 
     def load_extension(self, module_str):
         """Load an IPython extension by its module name.
 
-        If :func:`load_ipython_extension` returns anything, this function
-        will return that object.
+        Returns the string "already loaded" if the extension is already loaded,
+        otherwise None.
         """
+        if module_str in self.loaded:
+            return "already loaded"
+        
         from IPython.utils.syspathcontext import prepended_to_syspath
 
         if module_str not in sys.modules:
             with prepended_to_syspath(self.ipython_extension_dir):
                 __import__(module_str)
         mod = sys.modules[module_str]
         if self._call_load_ipython_extension(mod):
             self.loaded.add(module_str)
 
     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
         if not os.path.isdir(self.ipython_extension_dir):
             os.makedirs(self.ipython_extension_dir, mode = 0o777)
         
         if os.path.isfile(url):
             src_filename = os.path.basename(url)
             copy = copyfile
         else:
             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

IPython/core/magics/extension.py

@@ -1,76 +1,88 b''
 """Implementation of magic functions for the extension machinery.
 """
 #-----------------------------------------------------------------------------
 #  Copyright (c) 2012 The 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
 #-----------------------------------------------------------------------------
 
 # Stdlib
 import os
 
 # Our own packages
 from IPython.core.error import UsageError
 from IPython.core.magic import Magics, magics_class, line_magic
 
 #-----------------------------------------------------------------------------
 # Magic implementation classes
 #-----------------------------------------------------------------------------
 
 @magics_class
 class ExtensionMagics(Magics):
     """Magics to manage the IPython extensions system."""
 
     @line_magic
     def install_ext(self, parameter_s=''):
         """Download and install an extension from a URL, e.g.::
 
             %install_ext https://bitbucket.org/birkenfeld/ipython-physics/raw/d1310a2ab15d/physics.py
 
         The URL should point to an importable Python module - either a .py file
         or a .zip file.
 
         Parameters:
 
           -n filename : Specify a name for the file, rather than taking it from
                         the URL.
         """
         opts, args = self.parse_options(parameter_s, 'n:')
         try:
             filename = self.shell.extension_manager.install_extension(args,
                                                                  opts.get('n'))
         except ValueError as e:
             print e
             return
 
         filename = os.path.basename(filename)
         print "Installed %s. To use it, type:" % filename
         print "  %%load_ext %s" % os.path.splitext(filename)[0]
 
 
     @line_magic
     def load_ext(self, module_str):
         """Load an IPython extension by its module name."""
         if not module_str:
             raise UsageError('Missing module name.')
-        self.shell.extension_manager.load_extension(module_str)
+        if self.shell.extension_manager.load_extension(module_str) == 'already loaded':
+            print "The %s extension is already loaded. To reload it, use:" % module_str
+            print "  %reload_ext", module_str
 
     @line_magic
     def unload_ext(self, module_str):
-        """Unload an IPython extension by its module name."""
+        """Unload an IPython extension by its module name.
+        
+        Not all extensions can be unloaded, only those which define an
+        ``unload_ipython_extension`` function.
+        """
         if not module_str:
             raise UsageError('Missing module name.')
-        self.shell.extension_manager.unload_extension(module_str)
+        
+        res = self.shell.extension_manager.unload_extension(module_str)
+        
+        if res == 'no unload function':
+            print "The %s extension doesn't define how to unload it." % module_str
+        elif res == "not loaded":
+            print "The %s extension is not loaded." % module_str
 
     @line_magic
     def reload_ext(self, module_str):
         """Reload an IPython extension by its module name."""
         if not module_str:
             raise UsageError('Missing module name.')
         self.shell.extension_manager.reload_extension(module_str)