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Description:

djangofsa 2.8.0

Django friendly finite state machine support
This is a friendly fork which aims to ensure that the tests are passing with
the new python and django versions, the original django-fsm was written by
Mikhail Podgurskiy (kmmbvnr@gmail.com), https://github.com/viewflow/django-fsm

django-fsm adds simple declarative states management for django models.
If you need parallel task execution, view and background task code reuse
over different flows - check my new project django-viewflow:
https://github.com/viewflow/viewflow
Instead of adding some state field to a django model, and managing its
values by hand, you could use FSMState field and mark model methods with
the transition decorator. Your method could contain the side-effects
of the state change.
Nice introduction is available here:
https://gist.github.com/Nagyman/9502133
You may also take a look at django-fsm-admin project containing a mixin
and template tags to integrate django-fsm state transitions into the
django admin.
https://github.com/gadventures/django-fsm-admin
Transition logging support could be achived with help of django-fsm-log
package
https://github.com/gizmag/django-fsm-log
FSM really helps to structure the code, especially when a new developer
comes to the project. FSM is most effective when you use it for some
sequential steps.

Installation
$ pip install django-fsm
Or, for the latest git version
$ pip install -e git://github.com/kmmbvnr/django-fsm.git#egg=django-fsm
The library has full Python 3 support

Usage
Add FSMState field to your model
from django_fsm import FSMField, transition

class BlogPost(models.Model):
state = FSMField(default='new')
Use the transition decorator to annotate model methods
@transition(field=state, source='new', target='published')
def publish(self):
"""
This function may contain side-effects,
like updating caches, notifying users, etc.
The return value will be discarded.
"""
source parameter accepts a list of states, or an individual state.
You can use * for source, to allow switching to target from any
state. The field parameter accepts both a string attribute name or an
actual field instance.
If calling publish() succeeds without raising an exception, the state
field will be changed, but not written to the database.
from django_fsm import can_proceed

def publish_view(request, post_id):
post = get_object__or_404(BlogPost, pk=post_id)
if not can_proceed(post.publish):
raise PermissionDenied

post.publish()
post.save()
return redirect('/')
If some conditions are required to be met before changing the state, use
the conditions argument to transition. conditions must be a
list of functions taking one argument, the model instance. The function
must return either True or False or a value that evaluates to
True or False. If all functions return True, all conditions
are considered to be met and the transition is allowed to happen. If one
of the functions returns False, the transition will not happen.
These functions should not have any side effects.
You can use ordinary functions
def can_publish(instance):
# No publishing after 17 hours
if datetime.datetime.now().hour > 17:
return False
return True
Or model methods
def can_destroy(self):
return self.is_under_investigation()
Use the conditions like this:
@transition(field=state, source='new', target='published', conditions=[can_publish])
def publish(self):
"""
Side effects galore
"""

@transition(field=state, source='*', target='destroyed', conditions=[can_destroy])
def destroy(self):
"""
Side effects galore
"""
You could instantiate a field with protected=True option, that prevents
direct state field modification.
class BlogPost(models.Model):
state = FSMField(default='new', protected=True)

model = BlogPost()
model.state = 'invalid' # Raises AttributeError
Note that calling
refresh_from_db
on a model instance with a protected FSMField will cause an exception.

target
target state parameter could point to a specific state or django_fsm.State implementation
from django_fsm import FSMField, transition, RETURN_VALUE, GET_STATE
@transition(field=state,
source='*',
target=RETURN_VALUE('for_moderators', 'published'))
def publish(self, is_public=False):
return 'for_moderators' if is_public else 'published'

@transition(
field=state,
source='for_moderators',
target=GET_STATE(
lambda self, allowed: 'published' if allowed else 'rejected',
states=['published', 'rejected']))
def moderate(self, allowed):
self.allowed=allowed

custom properties
Custom properties can be added by providing a dictionary to the
custom keyword on the transition decorator.
@transition(field=state,
source='*',
target='onhold',
custom=dict(verbose='Hold for legal reasons'))
def legal_hold(self):
"""
Side effects galore
"""

on_error state
In case of transition method would raise exception, you can provide
specific target state
@transition(field=state, source='new', target='published', on_error='failed')
def publish(self):
"""
Some exception could happen here
"""

state_choices
Instead of passing two elements list choices you could use three
elements state_choices, the last element states for string reference
to model proxy class.
Base class instance would be dynamically changed to corresponding Proxy
class instance, depending on the state. Even for queryset results, you
will get Proxy class instances, even if QuerySet executed on base class.
Check the test
case
for example usage. Or read about implementation
internals

Permissions
It is common to have permissions attached to each model transition.
django-fsm handles this with permission keyword on the
transition decorator. permission accepts a permission string, or
callable that expects instance and user arguments and returns
True if user can perform the transition.
@transition(field=state, source='*', target='publish',
permission=lambda instance, user: not user.has_perm('myapp.can_make_mistakes'))
def publish(self):
pass

@transition(field=state, source='*', target='publish',
permission='myapp.can_remove_post')
def remove(self):
pass
You can check permission with has_transition_permission method
from django_fsm import has_transition_perm
def publish_view(request, post_id):
post = get_object_or_404(BlogPost, pk=post_id)
if not has_transition_perm(post.publish, request.user):
raise PermissionDenied

post.publish()
post.save()
return redirect('/')

Model methods
get_all_FIELD_transitions Enumerates all declared transitions
get_available_FIELD_transitions Returns all transitions data
available in current state
get_available_user_FIELD_transitions Enumerates all transitions data
available in current state for provided user

Foreign Key constraints support
If you store the states in the db table you could use FSMKeyField to
ensure Foreign Key database integrity.
In your model :
class DbState(models.Model):
id = models.CharField(primary_key=True, max_length=50)
label = models.CharField(max_length=255)

def __unicode__(self):
return self.label

class BlogPost(models.Model):
state = FSMKeyField(DbState, default='new')

@transition(field=state, source='new', target='published')
def publish(self):
pass
In your fixtures/initial_data.json :
[
{
"pk": "new",
"model": "myapp.dbstate",
"fields": {
"label": "_NEW_"
}
},
{
"pk": "published",
"model": "myapp.dbstate",
"fields": {
"label": "_PUBLISHED_"
}
}
]
Note : source and target parameters in @transition decorator use pk
values of DBState model as names, even if field “real” name is used,
without _id postfix, as field parameter.

Integer Field support
You can also use FSMIntegerField. This is handy when you want to use
enum style constants.
class BlogPostStateEnum(object):
NEW = 10
PUBLISHED = 20
HIDDEN = 30

class BlogPostWithIntegerField(models.Model):
state = FSMIntegerField(default=BlogPostStateEnum.NEW)

@transition(field=state, source=BlogPostStateEnum.NEW, target=BlogPostStateEnum.PUBLISHED)
def publish(self):
pass

Signals
django_fsm.signals.pre_transition and
django_fsm.signals.post_transition are called before and after
allowed transition. No signals on invalid transition are called.
Arguments sent with these signals:
sender The model class.
instance The actual instance being proceed
name Transition name
source Source model state
target Target model state

Optimistic locking
django-fsm provides optimistic locking mixin, to avoid concurrent
model state changes. If model state was changed in database
django_fsm.ConcurrentTransition exception would be raised on
model.save()
from django_fsm import FSMField, ConcurrentTransitionMixin

class BlogPost(ConcurrentTransitionMixin, models.Model):
state = FSMField(default='new')
For guaranteed protection against race conditions caused by concurrently
executed transitions, make sure:

Your transitions do not have any side effects except for changes in the database,
You always run the save() method on the object within django.db.transaction.atomic() block.

Following these recommendations, you can rely on
ConcurrentTransitionMixin to cause a rollback of all the changes that
have been executed in an inconsistent (out of sync) state, thus
practically negating their effect.

Drawing transitions
Renders a graphical overview of your models states transitions
You need pip install graphviz>=0.4 library and add django_fsm to
your INSTALLED_APPS:
INSTALLED_APPS = (
...
'django_fsm',
...
)
# Create a dot file
$ ./manage.py graph_transitions > transitions.dot

# Create a PNG image file only for specific model
$ ./manage.py graph_transitions -o blog_transitions.png myapp.Blog

Changelog

django-fsm 2.8.0 2019-12-08

Add compatibility tests with Django 3.0
Remove the dependency with django-guardians in the tests
change some django deprecated functions

django-fsm 2.7.2 2019-05-01

Add compatibility test with python 3.8
Add compatibility test with Django 2.2
- Refactor the models in tests, a migration

django-fsm 2.7.1 2019-03-04

Delivery on Pypi

django-fsm 2.7.0 2018-12-14

Fix the travis tests
Add compatibility test with python 3.7, remove 2.6 and 3.3
Add compatibility test with Django 2.0 and 2.1, remove 1.6, 1.8, 1.9 and 1.10

django-fsm 2.6.0 2017-06-08

Fix django 1.11 compatibility
Fix TypeError in graph_transitions command when using django’s lazy translations

django-fsm 2.5.0 2017-03-04

graph_transition command fix for django 1.10
graph_transition command supports GET_STATE targets
signal data extended with method args/kwargs and field
sets allowed to be passed to the transition decorator

django-fsm 2.4.0 2016-05-14

graph_transition commnad now works with multiple FSM’s per model
Add ability to set target state from transition return value or callable

django-fsm 2.3.0 2015-10-15

Add source state shortcut ‘+’ to specify transitions from all states except the target
Add object-level permission checks
Fix translated labels for graph of FSMIntegerField
Fix multiple signals for several transition decorators

django-fsm 2.2.1 2015-04-27

Improved exception message for unmet transition conditions.
Don’t send post transition signal in case of no state changes on
exception
Allow empty string as correct state value
Improved graphviz fsm visualisation
Clean django 1.8 warnings

django-fsm 2.2.0 2014-09-03

Support for class
substitution
to proxy classes depending on the state
Added ConcurrentTransitionMixin with optimistic locking support
Default db_index=True for FSMIntegerField removed
Graph transition code migrated to new graphviz library with python 3
support
Ability to change state on transition exception

django-fsm 2.1.0 2014-05-15

Support for attaching permission checks on model transitions

django-fsm 2.0.0 2014-03-15

Backward incompatible release
All public code import moved directly to django_fsm package
Correct support for several @transitions decorator with different
source states and conditions on same method
save parameter from transition decorator removed
get_available_FIELD_transitions return Transition data object
instead of tuple
Models got get_available_FIELD_transitions, even if field
specified as string reference
New get_all_FIELD_transitions method contributed to class

django-fsm 1.6.0 2014-03-15

FSMIntegerField and FSMKeyField support

django-fsm 1.5.1 2014-01-04

Ad-hoc support for state fields from proxy and inherited models

django-fsm 1.5.0 2013-09-17

Python 3 compatibility

django-fsm 1.4.0 2011-12-21

Add graph_transition command for drawing state transition picture

django-fsm 1.3.0 2011-07-28

Add direct field modification protection

django-fsm 1.2.0 2011-03-23

Add pre_transition and post_transition signals

django-fsm 1.1.0 2011-02-22

Add support for transition conditions
Allow multiple FSMField in one model
Contribute get_available_FIELD_transitions for model class

django-fsm 1.0.0 2010-10-12

Initial public release

copyright (c) 2010 Mikhail Podgurskiy
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the “Software”), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.