django1/django/core/management/base.py

"""
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
import traceback

import django
from django.core.exceptions import ImproperlyConfigured
from django.core.management.color import color_style
from django.utils.encoding import force_str
from django.utils.six import StringIO


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.

    """
    if options.settings:
        os.environ['DJANGO_SETTINGS_MODULE'] = options.settings
    if options.pythonpath:
        sys.path.insert(0, options.pythonpath)


class OutputWrapper(object):
    """
    Wrapper around stdout/stderr
    """
    def __init__(self, out, style_func=None, ending='\n'):
        self._out = out
        self.style_func = None
        if hasattr(out, 'isatty') and out.isatty():
            self.style_func = style_func
        self.ending = ending

    def __getattr__(self, name):
        return getattr(self._out, name)

    def write(self, msg, style_func=None, ending=None):
        ending = ending is None and self.ending or ending
        if ending and not msg.endswith(ending):
            msg += ending
        style_func = [f for f in (style_func, self.style_func, lambda x:x)
                      if f is not None][0]
        self._out.write(force_str(style_func(msg)))


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()`` or ``execute()`` raised any exception (e.g.
       ``CommandError``), ``run_from_argv()`` 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.

    ``leave_locale_alone``
        A boolean indicating whether the locale set in settings should be
        preserved during the execution of the command instead of being
        forcibly set to 'en-us'.

        Default value is ``False``.

        Make sure you know what you are doing if you decide to change the value
        of this option in your custom command because many of them create
        database content that is locale-sensitive (like permissions) and that
        content shouldn't contain any translations so making the locale differ
        from the de facto default 'en-us' can cause unintended effects.

        This option can't be False when the can_import_settings option is set
        to False too because attempting to set the locale needs access to
        settings. This condition will generate a CommandError.
    """
    # Metadata about this command.
    option_list = (
        make_option('-v', '--verbosity', action='store', dest='verbosity', default='1',
            type='choice', choices=['0', '1', '2', '3'],
            help='Verbosity level; 0=minimal output, 1=normal output, 2=verbose output, 3=very verbose output'),
        make_option('--settings',
            help='The Python path to a settings module, e.g. "myproject.settings.main". If this isn\'t provided, the DJANGO_SETTINGS_MODULE environment variable will be used.'),
        make_option('--pythonpath',
            help='A directory to add to the Python path, e.g. "/home/djangoprojects/myproject".'),
        make_option('--traceback', action='store_true',
            help='Print traceback on exception'),
    )
    help = ''
    args = ''

    # Configuration shortcuts that alter various logic.
    can_import_settings = True
    requires_model_validation = True
    output_transaction = False  # Whether to wrap the output in a "BEGIN; COMMIT;"
    leave_locale_alone = False

    def __init__(self):
        self.style = color_style()

    def get_version(self):
        """
        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)
        else:
            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. If the
        command raises a ``CommandError``, intercept it and print it sensibly
        to stderr.
        """
        parser = self.create_parser(argv[0], argv[1])
        options, args = parser.parse_args(argv[2:])
        handle_default_options(options)
        try:
            self.execute(*args, **options.__dict__)
        except Exception as e:
            # self.stderr is not guaranteed to be set here
            stderr = getattr(self, 'stderr', OutputWrapper(sys.stderr, self.style.ERROR))
            if options.traceback:
                stderr.write(traceback.format_exc())
            else:
                stderr.write('%s: %s' % (e.__class__.__name__, e))
            sys.exit(1)

    def execute(self, *args, **options):
        """
        Try to execute this command, performing model validation if
        needed (as controlled by the attribute
        ``self.requires_model_validation``, except if force-skipped).
        """
        self.stdout = OutputWrapper(options.get('stdout', sys.stdout))
        self.stderr = OutputWrapper(options.get('stderr', sys.stderr), self.style.ERROR)

        if self.can_import_settings:
            from django.conf import settings

        saved_locale = None
        if not self.leave_locale_alone:
            # Only mess with locales if we can assume we have a working
            # settings file, because django.utils.translation requires settings
            # (The final saying about whether the i18n machinery is active will be
            # found in the value of the USE_I18N setting)
            if not self.can_import_settings:
                raise CommandError("Incompatible values of 'leave_locale_alone' "
                                   "(%s) and 'can_import_settings' (%s) command "
                                   "options." % (self.leave_locale_alone,
                                                 self.can_import_settings))
            # Switch to US English, because django-admin.py creates database
            # content like permissions, and those shouldn't contain any
            # translations.
            from django.utils import translation
            saved_locale = translation.get_language()
            translation.activate('en-us')

        try:
            if self.requires_model_validation and not options.get('skip_validation'):
                self.validate()
            output = self.handle(*args, **options)
            if output:
                if self.output_transaction:
                    # This needs to be imported here, because it relies on
                    # settings.
                    from django.db import connections, DEFAULT_DB_ALIAS
                    connection = connections[options.get('database', DEFAULT_DB_ALIAS)]
                    if connection.ops.start_transaction_sql():
                        self.stdout.write(self.style.SQL_KEYWORD(connection.ops.start_transaction_sql()))
                self.stdout.write(output)
                if self.output_transaction:
                    self.stdout.write('\n' + self.style.SQL_KEYWORD("COMMIT;"))
        finally:
            if saved_locale is not None:
                translation.activate(saved_locale)

    def validate(self, app=None, display_num_errors=False):
        """
        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
        s = StringIO()
        num_errors = get_validation_errors(s, app)
        if num_errors:
            s.seek(0)
            error_text = s.read()
            raise CommandError("One or more models did not validate:\n%s" % error_text)
        if display_num_errors:
            self.stdout.write("%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):
        from django.db import models
        if not app_labels:
            raise CommandError('Enter at least one appname.')
        try:
            app_list = [models.get_app(app_label) for app_label in app_labels]
        except (ImproperlyConfigured, ImportError) as e:
            raise CommandError("%s. Are you sure your INSTALLED_APPS setting is correct?" % e)
        output = []
        for app in app_list:
            app_output = self.handle_app(app, **options)
            if app_output:
                output.append(app_output)
        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'

    def handle(self, *labels, **options):
        if not labels:
            raise CommandError('Enter at least one %s.' % self.label)

        output = []
        for label in labels:
            label_output = self.handle_label(label, **options)
            if label_output:
                output.append(label_output)
        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):
        if args:
            raise CommandError("Command doesn't accept any arguments")
        return self.handle_noargs(**options)

    def handle_noargs(self, **options):
        """
        Perform this command's actions.

        """
        raise NotImplementedError()