Address #6692: Only import a Command class when needed

docs/pip_sphinxext.py

@@ -9,14 +9,14 @@
 from docutils.statemachine import ViewList
 
 from pip._internal.cli import cmdoptions
-from pip._internal.commands import commands_dict as commands
+from pip._internal.commands import create_command
 
 
 class PipCommandUsage(rst.Directive):
     required_arguments = 1
 
     def run(self):
-        cmd = commands[self.arguments[0]]
+        cmd = create_command(self.arguments[0])
         usage = dedent(
             cmd.usage.replace('%prog', 'pip {}'.format(cmd.name))
         ).strip()
@@ -31,7 +31,8 @@ def run(self):
         node = nodes.paragraph()
         node.document = self.state.document
         desc = ViewList()
-        description = dedent(commands[self.arguments[0]].__doc__)
+        cmd = create_command(self.arguments[0])
+        description = dedent(cmd.__doc__)
         for line in description.split('\n'):
             desc.append(line, "")
         self.state.nested_parse(desc, 0, node)
@@ -95,7 +96,7 @@ class PipCommandOptions(PipOptions):
     required_arguments = 1
 
     def process_options(self):
-        cmd = commands[self.arguments[0]]()
+        cmd = create_command(self.arguments[0])
         self._format_options(
             cmd.parser.option_groups[0].option_list,
             cmd_name=cmd.name,

src/pip/_internal/__init__.py

@@ -39,7 +39,7 @@
 
 from pip._internal.cli.autocompletion import autocomplete
 from pip._internal.cli.main_parser import parse_command
-from pip._internal.commands import commands_dict
+from pip._internal.commands import create_command
 from pip._internal.exceptions import PipError
 from pip._internal.utils import deprecation
 from pip._vendor.urllib3.exceptions import InsecureRequestWarning
@@ -73,5 +73,6 @@ def main(args=None):
     except locale.Error as e:
         # setlocale can apparently crash if locale are uninitialized
         logger.debug("Ignoring error %s when setting locale", e)
-    command = commands_dict[cmd_name](isolated=("--isolated" in cmd_args))
+    command = create_command(cmd_name, isolated=("--isolated" in cmd_args))
+
     return command.main(cmd_args)

src/pip/_internal/cli/autocompletion.py

@@ -6,7 +6,7 @@
 import sys
 
 from pip._internal.cli.main_parser import create_main_parser
-from pip._internal.commands import commands_dict, get_summaries
+from pip._internal.commands import commands_dict, create_command
 from pip._internal.utils.misc import get_installed_distributions
 
 
@@ -23,7 +23,7 @@ def autocomplete():
     except IndexError:
         current = ''
 
-    subcommands = [cmd for cmd, summary in get_summaries()]
+    subcommands = list(commands_dict)
     options = []
     # subcommand
     try:
@@ -54,7 +54,7 @@ def autocomplete():
                     print(dist)
                 sys.exit(1)
 
-        subcommand = commands_dict[subcommand_name]()
+        subcommand = create_command(subcommand_name)
 
         for opt in subcommand.parser.option_list_all:
             if opt.help != optparse.SUPPRESS_HELP:

src/pip/_internal/cli/base_command.py

@@ -61,18 +61,20 @@ class Command(object):
     usage = None  # type: Optional[str]
     ignore_require_venv = False  # type: bool
 
-    def __init__(self, isolated=False):
-        # type: (bool) -> None
+    def __init__(self, name, summary, isolated=False):
+        # type: (str, str, bool) -> None
         parser_kw = {
             'usage': self.usage,
             'prog': '%s %s' % (get_prog(), self.name),
             'formatter': UpdatingDefaultsHelpFormatter(),
             'add_help_option': False,
-            'name': self.name,
+            'name': name,
             'description': self.__doc__,
             'isolated': isolated,
         }
 
+        self.name = name
+        self.summary = summary
         self.parser = ConfigOptionParser(**parser_kw)
 
         # Commands should add options to this option group

src/pip/_internal/cli/main_parser.py

@@ -9,11 +9,7 @@
     ConfigOptionParser,
     UpdatingDefaultsHelpFormatter,
 )
-from pip._internal.commands import (
-    commands_dict,
-    get_similar_commands,
-    get_summaries,
-)
+from pip._internal.commands import commands_dict, get_similar_commands
 from pip._internal.exceptions import CommandError
 from pip._internal.utils.misc import get_pip_version, get_prog
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
@@ -51,8 +47,10 @@ def create_main_parser():
     parser.main = True  # type: ignore
 
     # create command listing for description
-    command_summaries = get_summaries()
-    description = [''] + ['%-27s %s' % (i, j) for i, j in command_summaries]
+    description = [''] + [
+        '%-27s %s' % (name, command_info.summary)
+        for name, command_info in commands_dict.items()
+    ]
     parser.description = '\n'.join(description)
 
     return parser

src/pip/_internal/commands/__init__.py

@@ -3,57 +3,97 @@
 """
 from __future__ import absolute_import
 
-from pip._internal.commands.completion import CompletionCommand
-from pip._internal.commands.configuration import ConfigurationCommand
-from pip._internal.commands.debug import DebugCommand
-from pip._internal.commands.download import DownloadCommand
-from pip._internal.commands.freeze import FreezeCommand
-from pip._internal.commands.hash import HashCommand
-from pip._internal.commands.help import HelpCommand
-from pip._internal.commands.list import ListCommand
-from pip._internal.commands.check import CheckCommand
-from pip._internal.commands.search import SearchCommand
-from pip._internal.commands.show import ShowCommand
-from pip._internal.commands.install import InstallCommand
-from pip._internal.commands.uninstall import UninstallCommand
-from pip._internal.commands.wheel import WheelCommand
+import importlib
+from collections import namedtuple, OrderedDict
 
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
 
 if MYPY_CHECK_RUNNING:
-    from typing import List, Type
+    from typing import Any
     from pip._internal.cli.base_command import Command
 
-commands_order = [
-    InstallCommand,
-    DownloadCommand,
-    UninstallCommand,
-    FreezeCommand,
-    ListCommand,
-    ShowCommand,
-    CheckCommand,
-    ConfigurationCommand,
-    SearchCommand,
-    WheelCommand,
-    HashCommand,
-    CompletionCommand,
-    DebugCommand,
-    HelpCommand,
-]  # type: List[Type[Command]]
 
-commands_dict = {c.name: c for c in commands_order}
-
-
-def get_summaries(ordered=True):
-    """Yields sorted (command name, command summary) tuples."""
-
-    if ordered:
-        cmditems = _sort_commands(commands_dict, commands_order)
-    else:
-        cmditems = commands_dict.items()
-
-    for name, command_class in cmditems:
-        yield (name, command_class.summary)
+CommandInfo = namedtuple('CommandInfo', 'module_path, class_name, summary')
+
+# The ordering matters for help display.
+#    Also, even though the module path starts with the same
+# "pip._internal.commands" prefix in each case, we include the full path
+# because it makes testing easier (specifically when modifying commands_dict
+# in test setup / teardown by adding info for a FakeCommand class defined
+# in a test-related module).
+#    Finally, we need to pass an iterable of pairs here rather than a dict
+# so that the ordering won't be lost when using Python 2.7.
+commands_dict = OrderedDict([
+    ('install', CommandInfo(
+        'pip._internal.commands.install', 'InstallCommand',
+        'Install packages.',
+    )),
+    ('download', CommandInfo(
+        'pip._internal.commands.download', 'DownloadCommand',
+        'Download packages.',
+    )),
+    ('uninstall', CommandInfo(
+        'pip._internal.commands.uninstall', 'UninstallCommand',
+        'Uninstall packages.',
+    )),
+    ('freeze', CommandInfo(
+        'pip._internal.commands.freeze', 'FreezeCommand',
+        'Output installed packages in requirements format.',
+    )),
+    ('list', CommandInfo(
+        'pip._internal.commands.list', 'ListCommand',
+        'List installed packages.',
+    )),
+    ('show', CommandInfo(
+        'pip._internal.commands.show', 'ShowCommand',
+        'Show information about installed packages.',
+    )),
+    ('check', CommandInfo(
+        'pip._internal.commands.check', 'CheckCommand',
+        'Verify installed packages have compatible dependencies.',
+    )),
+    ('config', CommandInfo(
+        'pip._internal.commands.configuration', 'ConfigurationCommand',
+        'Manage local and global configuration.',
+    )),
+    ('search', CommandInfo(
+        'pip._internal.commands.search', 'SearchCommand',
+        'Search PyPI for packages.',
+    )),
+    ('wheel', CommandInfo(
+        'pip._internal.commands.wheel', 'WheelCommand',
+        'Build wheels from your requirements.',
+    )),
+    ('hash', CommandInfo(
+        'pip._internal.commands.hash', 'HashCommand',
+        'Compute hashes of package archives.',
+    )),
+    ('completion', CommandInfo(
+        'pip._internal.commands.completion', 'CompletionCommand',
+        'A helper command used for command completion.',
+    )),
+    ('debug', CommandInfo(
+        'pip._internal.commands.debug', 'DebugCommand',
+        'Show information useful for debugging.',
+    )),
+    ('help', CommandInfo(
+        'pip._internal.commands.help', 'HelpCommand',
+        'Show help for commands.',
+    )),
+])  # type: OrderedDict[str, CommandInfo]
+
+
+def create_command(name, **kwargs):
+    # type: (str, **Any) -> Command
+    """
+    Create an instance of the Command class with the given name.
+    """
+    module_path, class_name, summary = commands_dict[name]
+    module = importlib.import_module(module_path)
+    command_class = getattr(module, class_name)
+    command = command_class(name=name, summary=summary, **kwargs)
+
+    return command
 
 
 def get_similar_commands(name):
@@ -68,14 +108,3 @@ def get_similar_commands(name):
         return close_commands[0]
     else:
         return False
-
-
-def _sort_commands(cmddict, order):
-    def keyfn(key):
-        try:
-            return order.index(key[1])
-        except ValueError:
-            # unordered items should come last
-            return 0xff
-
-    return sorted(cmddict.items(), key=keyfn)

src/pip/_internal/commands/check.py

@@ -11,10 +11,9 @@
 
 class CheckCommand(Command):
     """Verify installed packages have compatible dependencies."""
-    name = 'check'
+
     usage = """
       %prog [options]"""
-    summary = 'Verify installed packages have compatible dependencies.'
 
     def run(self, options, args):
         package_set, parsing_probs = create_package_set_from_installed()

src/pip/_internal/commands/completion.py

@@ -47,8 +47,7 @@
 
 class CompletionCommand(Command):
     """A helper command to be used for command completion."""
-    name = 'completion'
-    summary = 'A helper command used for command completion.'
+
     ignore_require_venv = True
 
     def __init__(self, *args, **kw):

src/pip/_internal/commands/configuration.py

@@ -34,7 +34,6 @@ class ConfigurationCommand(Command):
         default.
     """
 
-    name = 'config'
     usage = """
         %prog [<file-option>] list
         %prog [<file-option>] [--editor <editor-path>] edit
@@ -44,8 +43,6 @@ class ConfigurationCommand(Command):
         %prog [<file-option>] unset name
     """
 
-    summary = "Manage local and global configuration."
-
     def __init__(self, *args, **kwargs):
         super(ConfigurationCommand, self).__init__(*args, **kwargs)
 

src/pip/_internal/commands/debug.py

@@ -77,10 +77,8 @@ class DebugCommand(Command):
     Display debug information.
     """
 
-    name = 'debug'
     usage = """
       %prog <options>"""
-    summary = 'Show information useful for debugging.'
     ignore_require_venv = True
 
     def __init__(self, *args, **kw):

src/pip/_internal/commands/download.py

@@ -29,7 +29,6 @@ class DownloadCommand(RequirementCommand):
     pip also supports downloading from "requirements files", which provide
     an easy way to specify a whole environment to be downloaded.
     """
-    name = 'download'
 
     usage = """
       %prog [options] <requirement specifier> [package-index-options] ...
@@ -38,8 +37,6 @@ class DownloadCommand(RequirementCommand):
       %prog [options] <local project path> ...
       %prog [options] <archive url/path> ..."""
 
-    summary = 'Download packages.'
-
     def __init__(self, *args, **kw):
         super(DownloadCommand, self).__init__(*args, **kw)
 

src/pip/_internal/commands/freeze.py

@@ -18,10 +18,9 @@ class FreezeCommand(Command):
 
     packages are listed in a case-insensitive sorted order.
     """
-    name = 'freeze'
+
     usage = """
       %prog [options]"""
-    summary = 'Output installed packages in requirements format.'
     log_streams = ("ext://sys.stderr", "ext://sys.stderr")
 
     def __init__(self, *args, **kw):

src/pip/_internal/commands/hash.py

@@ -18,11 +18,9 @@ class HashCommand(Command):
 
     These can be used with --hash in a requirements file to do repeatable
     installs.
-
     """
-    name = 'hash'
+
     usage = '%prog [options] <file> ...'
-    summary = 'Compute hashes of package archives.'
     ignore_require_venv = True
 
     def __init__(self, *args, **kw):