"""
Base classes for writing management commands (named commands which can
be executed through ``django-admin.py`` or ``manage.py``).
"""
from __future__ import unicode_literals
import os
import sys
from optparse import make_option, OptionParser
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
[docs]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 = self.ending if ending is None else 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)))
[docs]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 if it creates database content
that is locale-sensitive and such content shouldn't contain any
translations (like it happens e.g. with django.contrim.auth
permissions) as making the locale differ from the de facto default
'en-us' might 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='Raise 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()
[docs] 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. If the ``--traceback`` option is present or the raised
``Exception`` is not ``CommandError``, raise it.
"""
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:
if options.traceback or not isinstance(e, CommandError):
raise
# self.stderr is not guaranteed to be set here
stderr = getattr(self, 'stderr', OutputWrapper(sys.stderr, self.style.ERROR))
stderr.write('%s: %s' % (e.__class__.__name__, e))
sys.exit(1)
[docs] 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)
[docs] 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, '' if num_errors == 1 else 's'))
[docs] 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()
Oct 03, 2017