Add some docstrings to the base classes for management commands. Refs #9170.

"""

Base classes for writing management commands (named commands which can

be executed through ``django-admin.py`` or ``manage.py``).

"""

import os

import sys

from optparse import make_option, OptionParser

    from sets import Set as set     # For Python 2.3

class CommandError(Exception):

    """

    Exception class indicating a problem while executing a management

    command.

    If this exception is raised during the execution of a management

    command, it will be caught and turned into a nicely-printed error

    message to the appropriate output stream (i.e., stderr); as a

    result, raising this exception (with a sensible description of the

    error) is the preferred way to indicate that something has gone

    wrong in the execution of a command.

    """

    pass

def handle_default_options(options):

    """

    Include any default options that all commands should accept

    here so that ManagementUtility can handle them before searching

    for user commands.

    Include any default options that all commands should accept here

    so that ManagementUtility can handle them before searching for

    user commands.

    """

    if options.settings:

        os.environ['DJANGO_SETTINGS_MODULE'] = options.settings

        sys.path.insert(0, options.pythonpath)

class BaseCommand(object):

    """

    The base class from which all management commands ultimately

    derive.

    Use this class if you want access to all of the mechanisms which

    parse the command-line arguments and work out what code to call in

    response; if you don't need to change any of that behavior,

    consider using one of the subclasses defined in this file.

    If you are interested in overriding/customizing various aspects of

    the command-parsing and -execution behavior, the normal flow works

    as follows:

    1. ``django-admin.py`` or ``manage.py`` loads the command class

       and calls its ``run_from_argv()`` method.

    2. The ``run_from_argv()`` method calls ``create_parser()`` to get

       an ``OptionParser`` for the arguments, parses them, performs

       any environment changes requested by options like

       ``pythonpath``, and then calls the ``execute()`` method,

       passing the parsed arguments.

    3. The ``execute()`` method attempts to carry out the command by

       calling the ``handle()`` method with the parsed arguments; any

       output produced by ``handle()`` will be printed to standard

       output and, if the command is intended to produce a block of

       SQL statements, will be wrapped in ``BEGIN`` and ``COMMIT``.

    4. If ``handle()`` raised a ``ComandError``, ``execute()`` will

       instead print an error message to ``stderr``.

    Thus, the ``handle()`` method is typically the starting point for

    subclasses; many built-in commands and command types either place

    all of their logic in ``handle()``, or perform some additional

    parsing work in ``handle()`` and then delegate from it to more

    specialized methods as needed.

    Several attributes affect behavior at various steps along the way:

    ``args``

        A string listing the arguments accepted by the command,

        suitable for use in help messages; e.g., a command which takes

        a list of application names might set this to '<appname

        appname ...>'.

    ``can_import_settings``

        A boolean indicating whether the command needs to be able to

        import Django settings; if ``True``, ``execute()`` will verify

        that this is possible before proceeding. Default value is

        ``True``.

    ``help``

        A short description of the command, which will be printed in

        help messages.

    ``option_list``

        This is the list of ``optparse`` options which will be fed

        into the command's ``OptionParser`` for parsing arguments.

    ``output_transaction``

        A boolean indicating whether the command outputs SQL

        statements; if ``True``, the output will automatically be

        wrapped with ``BEGIN;`` and ``COMMIT;``. Default value is

        ``False``.

    ``requires_model_validation``

        A boolean; if ``True``, validation of installed models will be

        performed prior to executing the command. Default value is

        ``True``. To validate an individual application's models

        rather than all applications' models, call

        ``self.validate(app)`` from ``handle()``, where ``app`` is the

        application's Python module.

    """

    # Metadata about this command.

    option_list = (

        make_option('--settings',

    def get_version(self):

        """

        Returns the Django version, which should be correct for all built-in

        Django commands. User-supplied commands should override this method.

        Return the Django version, which should be correct for all

        built-in Django commands. User-supplied commands should

        override this method.

        """

        return django.get_version()

    def usage(self, subcommand):

        """

        Return a brief description of how to use this command, by

        default from the attribute ``self.help``.

        """

        usage = '%%prog %s [options] %s' % (subcommand, self.args)

        if self.help:

            return '%s\n\n%s' % (usage, self.help)

            return usage

    def create_parser(self, prog_name, subcommand):

        """

        Create and return the ``OptionParser`` which will be used to

        parse the arguments to this command.

        """

        return OptionParser(prog=prog_name,

                            usage=self.usage(subcommand),

                            version=self.get_version(),

                            option_list=self.option_list)

    def print_help(self, prog_name, subcommand):

        """

        Print the help message for this command, derived from

        ``self.usage()``.

        """

        parser = self.create_parser(prog_name, subcommand)

        parser.print_help()

    def run_from_argv(self, argv):

        """

        Set up any environment changes requested (e.g., Python path

        and Django settings), then run this command.

        """

        parser = self.create_parser(argv[0], argv[1])

        options, args = parser.parse_args(argv[2:])

        handle_default_options(options)

        self.execute(*args, **options.__dict__)

    def execute(self, *args, **options):

        """

        Try to execute this command, performing model validation if

        needed (as controlled by the attribute

        ``self.requires_model_validation``). If the command raises a

        ``CommandError``, intercept it and print it sensibly to

        stderr.

        """

        # Switch to English, because django-admin.py creates database content

        # like permissions, and those shouldn't contain any translations.

        # But only do this if we can assume we have a working settings file,

        Validates the given app, raising CommandError for any errors.

        If app is None, then this will validate all installed apps.

        """

        from django.core.management.validation import get_validation_errors

        try:

            print "%s error%s found" % (num_errors, num_errors != 1 and 's' or '')

    def handle(self, *args, **options):

        """

        The actual logic of the command. Subclasses must implement

        this method.

        """

        raise NotImplementedError()

class AppCommand(BaseCommand):

    """

    A management command which takes one or more installed application

    names as arguments, and does something with each of them.

    Rather than implementing ``handle()``, subclasses must implement

    ``handle_app()``, which will be called once for each application.

    """

    args = '<appname appname ...>'

    def handle(self, *app_labels, **options):

        return '\n'.join(output)

    def handle_app(self, app, **options):

        """

        Perform the command's actions for ``app``, which will be the

        Python module corresponding to an application name given on

        the command line.

        """

        raise NotImplementedError()

class LabelCommand(BaseCommand):

    """

    A management command which takes one or more arbitrary arguments

    (labels) on the command line, and does something with each of

    them.

    Rather than implementing ``handle()``, subclasses must implement

    ``handle_label()``, which will be called once for each label.

    If the arguments should be names of installed applications, use

    ``AppCommand`` instead.

    """

    args = '<label label ...>'

    label = 'label'

        return '\n'.join(output)

    def handle_label(self, label, **options):

        """

        Perform the command's actions for ``label``, which will be the

        string as given on the command line.

        """

        raise NotImplementedError()

class NoArgsCommand(BaseCommand):

    """

    A command which takes no arguments on the command line.

    Rather than implementing ``handle()``, subclasses must implement

    ``handle_noargs()``; ``handle()`` itself is overridden to ensure

    no arguments are passed to the command.

    Attempting to pass arguments will raise ``CommandError``.

    """

    args = ''

    def handle(self, *args, **options):

        return self.handle_noargs(**options)

    def handle_noargs(self, **options):

        """

        Perform this command's actions.

        """

        raise NotImplementedError()

def copy_helper(style, app_or_project, name, directory, other_name=''):

    """

    Copies either a Django application layout template or a Django project

    layout template into the specified directory.

    """

    # style -- A color style object (see django.core.management.color).

    # app_or_project -- The string 'app' or 'project'.

                sys.stderr.write(style.NOTICE("Notice: Couldn't set permission bits on %s. You're probably using an uncommon filesystem setup. No problem.\n" % path_new))

def _make_writeable(filename):

    "Makes sure that the file is writeable. Useful if our source is read-only."

    """

    Make sure that the file is writeable. Useful if our source is

    read-only.

    """

    import stat

    if sys.platform.startswith('java'):

        # On Jython there is no os.access()