remove global command instances

Rework the way commands are defined, loaded and ran in pip:

 - Commands are instantiated on demand in pip.main().

 - A command 'registry' - mapping of command names to command classes in
   pip.commands.__init__.

 - Remove deferred command module loading.

pip/__init__.py

@@ -6,12 +6,11 @@ import sys
 import re
 import difflib
 
-from pip.basecommand import command_dict, load_command, load_all_commands, command_names
-from pip.baseparser import parser
-from pip.exceptions import InstallationError
+from pip.exceptions import InstallationError, CommandError, PipError
 from pip.log import logger
 from pip.util import get_installed_distributions, get_prog
 from pip.vcs import git, mercurial, subversion, bazaar  # noqa
+from pip.commands import commands, get_similar_commands, get_summaries
 
 
 # The version as used in the setup.py and the docs conf.py
@@ -33,8 +32,8 @@ def autocomplete():
         current = cwords[cword - 1]
     except IndexError:
         current = ''
-    load_all_commands()
-    subcommands = [cmd for cmd, cls in command_dict.items() if not cls.hidden]
+
+    subcommands = [cmd for cmd, cls in commands.items() if not cls.hidden]
     options = []
     # subcommand
     try:
@@ -58,7 +57,7 @@ def autocomplete():
                 for dist in installed:
                     print(dist)
                 sys.exit(1)
-        subcommand = command_dict.get(subcommand_name)
+        subcommand = commands.get(subcommand_name)
         options += [(opt.get_opt_string(), opt.nargs)
                     for opt in subcommand.parser.option_list
                     if opt.help != optparse.SUPPRESS_HELP]

pip/basecommand.py

@@ -8,7 +8,6 @@ import tempfile
 import traceback
 import time
 
-from pip import commands
 from pip.log import logger
 from pip.baseparser import parser, ConfigOptionParser, UpdatingDefaultsHelpFormatter
 from pip.download import urlopen
@@ -19,10 +18,8 @@ from pip.status_codes import SUCCESS, ERROR, UNKNOWN_ERROR, VIRTUALENV_NOT_FOUND
 from pip.util import get_prog
 
 
-__all__ = ['command_dict', 'Command', 'load_all_commands',
-           'load_command', 'command_names']
+__all__ = ['Command']
 
-command_dict = {}
 
 # for backwards compatibiliy
 get_proxy = urlopen.get_proxy
@@ -179,23 +176,3 @@ def open_logfile(filename, mode='a'):
         log_fp.write('%s run on %s\n' % (sys.argv[0], time.strftime('%c')))
     return log_fp
 
-
-def load_command(name):
-    full_name = 'pip.commands.%s' % name
-    if full_name in sys.modules:
-        return
-    try:
-        __import__(full_name)
-    except ImportError:
-        pass
-
-
-def load_all_commands():
-    for name in command_names():
-        load_command(name)
-
-
-def command_names():
-    names = set((pkg[1] for pkg in walk_packages(path=commands.__path__)))
-    return list(names)
-

pip/commands/__init__.py

@@ -1 +1,57 @@
-#
+"""
+Package containing all pip commands
+"""
+
+
+from pip.commands.bundle     import BundleCommand
+from pip.commands.completion import CompletionCommand
+from pip.commands.freeze     import FreezeCommand
+from pip.commands.help       import HelpCommand
+from pip.commands.search     import SearchCommand
+from pip.commands.show       import ShowCommand
+from pip.commands.install    import InstallCommand
+from pip.commands.uninstall  import UninstallCommand
+from pip.commands.unzip      import UnzipCommand
+from pip.commands.zip        import ZipCommand
+
+
+commands = {
+    BundleCommand.name      : BundleCommand,
+    CompletionCommand.name  : CompletionCommand,
+    FreezeCommand.name      : FreezeCommand,
+    HelpCommand.name        : HelpCommand,
+    SearchCommand.name      : SearchCommand,
+    ShowCommand.name        : ShowCommand,
+    InstallCommand.name     : InstallCommand,
+    UninstallCommand.name   : UninstallCommand,
+    UnzipCommand.name       : UnzipCommand,
+    ZipCommand.name         : ZipCommand,
+}
+
+
+def get_summaries(ignore_hidden=True):
+    """Return a sorted list of (command name, command summary)."""
+    items = []
+
+    for name, command_class in commands.items():
+        if ignore_hidden and command_class.hidden:
+            continue
+
+        items.append( (name, command_class.summary) )
+
+    return sorted(items)
+
+
+def get_similar_commands(name):
+    """Command name auto-correct."""
+    from difflib import get_close_matches
+
+    close_commands = get_close_matches(name, commands.keys())
+
+    if close_commands:
+        guess = close_commands[0]
+    else:
+        guess = False
+
+    return guess
+

pip/commands/bundle.py

@@ -34,5 +34,3 @@ class BundleCommand(InstallCommand):
         requirement_set = super(BundleCommand, self).run(options, args)
         return requirement_set
 
-
-BundleCommand()

pip/commands/completion.py

@@ -56,5 +56,3 @@ class CompletionCommand(Command):
             print(BASE_COMPLETION % {'script': script, 'shell': options.shell})
         else:
             sys.stderr.write('ERROR: You must pass %s\n' % ' or '.join(shell_options))
-
-CompletionCommand()

pip/commands/freeze.py

@@ -106,6 +106,3 @@ class FreezeCommand(Command):
             f.write('## The following requirements were added by pip --freeze:\n')
         for installation in sorted(installations.values(), key=lambda x: x.name):
             f.write(str(installation))
-
-
-FreezeCommand()

pip/commands/help.py

@@ -30,4 +30,3 @@ class HelpCommand(Command):
             print('  %s: %s' % (command.name, command.summary))
         return SUCCESS
 
-HelpCommand()

pip/commands/install.py

@@ -292,6 +292,3 @@ class InstallCommand(Command):
                     )
             shutil.rmtree(temp_target_dir)
         return requirement_set
-
-
-InstallCommand()

pip/commands/search.py

@@ -124,6 +124,3 @@ def compare_versions(version1, version2):
 
 def highest_version(versions):
     return reduce((lambda v1, v2: compare_versions(v1, v2) == 1 and v1 or v2), versions)
-
-
-SearchCommand()

pip/commands/show.py

@@ -73,6 +73,3 @@ def print_results(distributions, list_all_files):
                     logger.notify("  %s" % line.strip())
             else:
                 logger.notify("Cannot locate installed-files.txt")
-
-
-ShowCommand()

pip/commands/uninstall.py

@@ -39,5 +39,3 @@ class UninstallCommand(Command):
             raise InstallationError('You must give at least one requirement '
                 'to %(name)s (see "pip help %(name)s")' % dict(name=self.name))
         requirement_set.uninstall(auto_confirm=options.yes)
-
-UninstallCommand()

pip/commands/unzip.py

@@ -4,6 +4,3 @@ from pip.commands.zip import ZipCommand
 class UnzipCommand(ZipCommand):
     name = 'unzip'
     summary = 'Unzip individual packages'
-
-
-UnzipCommand()

pip/commands/zip.py

@@ -341,6 +341,3 @@ class ZipCommand(Command):
                          if not f.lower().endswith('.pyc')]
             total += len(filenames)
         return total
-
-
-ZipCommand()