WIP make content models swappable, closes #1160

(It's marked as WIP because tests are far from passing, and we can
always discuss the coding style and naming.)

Any of the following models can now be swapped by your own version:

* Page
* RichTextPage
* Link
* BlogPost
* BlogCategory
* Form
* FormEntry
* Field
* FieldEntry
* Gallery
* GalleryImage

So you can keep the same features and API but add fields, methods, inherit from
other classes (geo models for geo fields, third-party models...), etc.
without having to resort to model inheritance.

Just make sure you inherit from each respective abstract base class.

Contrary to my first submission, I kept the BaseXXX classes for a
smoother transition path.

I didn't change imports or references in the admin modules, I followed
UserAdmin conventions here. You'll have to explicitly register, e.g.  PageAdmin
to your swapped Page model.

No docs update yet, let's first agree on code and naming conventions, what will
become the public API for users. This includes whether we provide
default values in the template project settings or in the code.

I also guess this deprecates the field injection feature, before removing it in
a future major version.

Besides that, it must be 100% compatible, no test changes apart from imports.

mezzanine/blog/__init__.py

@@ -5,3 +5,12 @@
 from __future__ import unicode_literals
 
 from mezzanine import __version__  # noqa
+from mezzanine.utils.models import get_swappable_model
+
+
+def get_post_model():
+    return get_swappable_model("BLOG_POST_MODEL")
+
+
+def get_category_model():
+    return get_swappable_model("BLOG_CATEGORY_MODEL")

mezzanine/blog/feeds.py

@@ -8,16 +8,19 @@
 from django.utils.feedgenerator import Atom1Feed
 from django.utils.html import strip_tags
 
-from mezzanine.blog.models import BlogPost, BlogCategory
+from mezzanine.blog import get_post_model, get_category_model
 from mezzanine.conf import settings
 from mezzanine.core.templatetags.mezzanine_tags import richtext_filters
 from mezzanine.core.request import current_request
 from mezzanine.generic.models import Keyword
+from mezzanine.utils.apps import pages_installed
 from mezzanine.utils.html import absolute_urls
 from mezzanine.utils.sites import current_site_id
 
 
 User = get_user_model()
+BlogPost = get_post_model()
+BlogCategory = get_category_model()
 
 try:
     unicode
@@ -43,8 +46,9 @@ def __init__(self, *args, **kwargs):
         super(PostsRSS, self).__init__(*args, **kwargs)
         self._public = True
         page = None
-        if "mezzanine.pages" in settings.INSTALLED_APPS:
-            from mezzanine.pages.models import Page
+        if pages_installed():
+            from mezzanine.pages import get_page_model
+            Page = get_page_model()
             try:
                 page = Page.objects.published().get(slug=settings.BLOG_SLUG)
             except Page.DoesNotExist:

mezzanine/blog/forms.py

@@ -2,10 +2,12 @@
 
 from django import forms
 
-from mezzanine.blog.models import BlogPost
+from mezzanine.blog import get_post_model
 from mezzanine.core.models import CONTENT_STATUS_DRAFT
 
 
+BlogPost = get_post_model()
+
 # These fields need to be in the form, hidden, with default values,
 # since it posts to the blog post admin, which includes these fields
 # and will use empty values instead of the model defaults, without

mezzanine/blog/management/base.py

@@ -12,15 +12,18 @@
 from django.utils.encoding import force_text
 from django.utils.html import strip_tags
 
-from mezzanine.blog.models import BlogPost, BlogCategory
+from mezzanine.blog import get_post_model, get_category_model
 from mezzanine.conf import settings
 from mezzanine.core.models import CONTENT_STATUS_DRAFT
 from mezzanine.core.models import CONTENT_STATUS_PUBLISHED
 from mezzanine.generic.models import Keyword, ThreadedComment
-from mezzanine.pages.models import RichTextPage
+from mezzanine.pages import get_rich_text_page_model
 from mezzanine.utils.html import decode_entities
 
 User = get_user_model()
+BlogPost = get_post_model()
+BlogCategory = get_category_model()
+RichTextPage = get_rich_text_page_model()
 
 
 class BaseImporterCommand(BaseCommand):

mezzanine/blog/migrations/0001_initial.py

@@ -24,6 +24,7 @@ class Migration(migrations.Migration):
                 ('site', models.ForeignKey(editable=False, to='sites.Site', on_delete=models.CASCADE)),
             ],
             options={
+                'swappable': 'BLOG_CATEGORY_MODEL',
                 'ordering': ('title',),
                 'verbose_name': 'Blog Category',
                 'verbose_name_plural': 'Blog Categories',
@@ -60,6 +61,7 @@ class Migration(migrations.Migration):
                 ('user', models.ForeignKey(related_name='blogposts', verbose_name='Author', to=settings.AUTH_USER_MODEL, on_delete=models.CASCADE)),
             ],
             options={
+                'swappable': 'BLOG_POST_MODEL',
                 'ordering': ('-publish_date',),
                 'verbose_name': 'Blog post',
                 'verbose_name_plural': 'Blog posts',

mezzanine/blog/models.py

@@ -12,12 +12,12 @@
 from mezzanine.utils.models import AdminThumbMixin, upload_to
 
 
-class BlogPost(Displayable, Ownable, RichText, AdminThumbMixin):
+class AbstractBlogPost(Displayable, Ownable, RichText, AdminThumbMixin):
     """
     A blog post.
     """
 
-    categories = models.ManyToManyField("BlogCategory",
+    categories = models.ManyToManyField(settings.BLOG_CATEGORY_MODEL,
                                         verbose_name=_("Categories"),
                                         blank=True, related_name="blogposts")
     allow_comments = models.BooleanField(verbose_name=_("Allow comments"),
@@ -33,6 +33,7 @@ class BlogPost(Displayable, Ownable, RichText, AdminThumbMixin):
     admin_thumb_field = "featured_image"
 
     class Meta:
+        abstract = True
         verbose_name = _("Blog post")
         verbose_name_plural = _("Blog posts")
         ordering = ("-publish_date",)
@@ -64,16 +65,29 @@ def get_absolute_url(self):
         return reverse(url_name, kwargs=kwargs)
 
 
-class BlogCategory(Slugged):
+class BlogPost(AbstractBlogPost):
+
+    class Meta(AbstractBlogPost.Meta):
+        swappable = 'BLOG_POST_MODEL'
+
+
+class AbstractBlogCategory(Slugged):
     """
     A category for grouping blog posts into a series.
     """
 
     class Meta:
+        abstract = True
         verbose_name = _("Blog Category")
         verbose_name_plural = _("Blog Categories")
         ordering = ("title",)
 
     @models.permalink
     def get_absolute_url(self):
         return ("blog_post_list_category", (), {"category": self.slug})
+
+
+class BlogCategory(AbstractBlogCategory):
+
+    class Meta(AbstractBlogCategory.Meta):
+        swappable = 'BLOG_CATEGORY_MODEL'

mezzanine/blog/templatetags/blog_tags.py

@@ -5,12 +5,14 @@
 from django.db.models import Count, Q
 from django.utils import timezone
 
+from mezzanine.blog import get_post_model, get_category_model
 from mezzanine.blog.forms import BlogPostForm
-from mezzanine.blog.models import BlogPost, BlogCategory
 from mezzanine.generic.models import Keyword
 from mezzanine import template
 
 User = get_user_model()
+BlogPost = get_post_model()
+BlogCategory = get_category_model()
 
 register = template.Library()
 

mezzanine/blog/tests.py

@@ -14,13 +14,19 @@
 from django.template import Context, Template
 from django.test import override_settings
 
-from mezzanine.blog.models import BlogPost
+from mezzanine.blog import get_post_model
 from mezzanine.conf import settings
 from mezzanine.core.models import CONTENT_STATUS_PUBLISHED
-from mezzanine.pages.models import Page, RichTextPage
+from mezzanine.pages import get_page_model, get_rich_text_page_model
+from mezzanine.utils.apps import accounts_installed, pages_installed
 from mezzanine.utils.tests import TestCase
 
 
+BlogPost = get_post_model()
+Page = get_page_model()
+RichTextPage = get_rich_text_page_model()
+
+
 class BlogTests(TestCase):
 
     def test_blog_views(self):
@@ -38,8 +44,7 @@ def test_blog_views(self):
         response = self.client.get(blog_post.get_absolute_url())
         self.assertEqual(response.status_code, 200)
 
-    @skipUnless("mezzanine.accounts" in settings.INSTALLED_APPS and
-                "mezzanine.pages" in settings.INSTALLED_APPS,
+    @skipUnless(accounts_installed() and pages_installed(),
                 "accounts and pages apps required")
     def test_login_protected_blog(self):
         """

mezzanine/blog/translation.py

@@ -2,7 +2,11 @@
 from mezzanine.core.translation import (TranslatedSlugged,
                                         TranslatedDisplayable,
                                         TranslatedRichText)
-from mezzanine.blog.models import BlogCategory, BlogPost
+from mezzanine.blog import get_post_model, get_category_model
+
+
+BlogPost = get_post_model()
+BlogCategory = get_category_model()
 
 
 class TranslatedBlogPost(TranslatedDisplayable, TranslatedRichText):
@@ -12,5 +16,6 @@ class TranslatedBlogPost(TranslatedDisplayable, TranslatedRichText):
 class TranslatedBlogCategory(TranslatedSlugged):
     fields = ()
 
+
 translator.register(BlogCategory, TranslatedBlogCategory)
 translator.register(BlogPost, TranslatedBlogPost)

mezzanine/blog/views.py

@@ -9,13 +9,15 @@
 from django.template.response import TemplateResponse
 from django.utils.translation import ugettext_lazy as _
 
-from mezzanine.blog.models import BlogPost, BlogCategory
+from mezzanine.blog import get_post_model, get_category_model
 from mezzanine.blog.feeds import PostsRSS, PostsAtom
 from mezzanine.conf import settings
 from mezzanine.generic.models import Keyword
 from mezzanine.utils.views import paginate
 
 User = get_user_model()
+BlogPost = get_post_model()
+BlogCategory = get_category_model()
 
 
 def blog_post_list(request, tag=None, year=None, month=None, username=None,

mezzanine/boot/lazy_admin.py

@@ -7,6 +7,7 @@
     NotRegistered, AlreadyRegistered)
 from django.shortcuts import redirect
 
+from mezzanine.utils.apps import pages_installed
 from mezzanine.utils.importing import import_dotted_path
 
 
@@ -104,7 +105,7 @@ def urls(self):
             url("^displayable_links.js$", displayable_links_js,
                 name="displayable_links_js"),
         ]
-        if "mezzanine.pages" in settings.INSTALLED_APPS:
+        if pages_installed():
             from mezzanine.pages.views import admin_page_ordering
             urls.append(url("^admin_page_ordering/$", admin_page_ordering,
                             name="admin_page_ordering"))

mezzanine/conf/translation.py

@@ -5,4 +5,5 @@
 class TranslatedSetting(TranslationOptions):
     fields = ('value',)
 
+
 translator.register(Setting, TranslatedSetting)

mezzanine/core/management/commands/createdb.py

@@ -115,7 +115,8 @@ def create_pages(self):
             if self.verbosity >= 1:
                 print("\nCreating demo pages: About us, Contact form, "
                         "Gallery ...\n")
-            from mezzanine.galleries.models import Gallery
+            from mezzanine.galleries import get_gallery_model
+            Gallery = get_gallery_model()
             call_command("loaddata", "mezzanine_optional.json")
             zip_name = "gallery.zip"
             copy_test_to_media("mezzanine.core", zip_name)

mezzanine/core/models.py

@@ -25,14 +25,11 @@
 from mezzanine.core.managers import DisplayableManager, CurrentSiteManager
 from mezzanine.generic.fields import KeywordsField
 from mezzanine.utils.html import TagCloser
-from mezzanine.utils.models import base_concrete_model, get_user_model_name
+from mezzanine.utils.models import base_concrete_model
 from mezzanine.utils.sites import current_site_id, current_request
 from mezzanine.utils.urls import admin_url, slugify, unique_slug
 
 
-user_model_name = get_user_model_name()
-
-
 def wrapped_manager(klass):
     if settings.USE_MODELTRANSLATION:
         from modeltranslation.manager import MultilingualManager
@@ -507,8 +504,9 @@ class Ownable(models.Model):
     Abstract model that provides ownership of an object for a user.
     """
 
-    user = models.ForeignKey(user_model_name, on_delete=models.CASCADE,
-        verbose_name=_("Author"), related_name="%(class)ss")
+    user = models.ForeignKey(settings.AUTH_USER_MODEL,
+        on_delete=models.CASCADE, verbose_name=_("Author"),
+        related_name="%(class)ss")
 
     class Meta:
         abstract = True
@@ -577,8 +575,9 @@ class SitePermission(models.Model):
     access.
     """
 
-    user = models.OneToOneField(user_model_name, on_delete=models.CASCADE,
-        verbose_name=_("Author"), related_name="%(class)ss")
+    user = models.OneToOneField(settings.AUTH_USER_MODEL,
+        on_delete=models.CASCADE, verbose_name=_("Author"),
+        related_name="%(class)ss")
     sites = models.ManyToManyField("sites.Site", blank=True,
                                    verbose_name=_("Sites"))
 

mezzanine/core/sitemaps.py

@@ -3,14 +3,14 @@
 from django.contrib.sitemaps import Sitemap
 from django.contrib.sites.models import Site
 
-from mezzanine.conf import settings
 from mezzanine.core.models import Displayable
+from mezzanine.utils.apps import blog_installed
 from mezzanine.utils.sites import current_site_id
 
 
-blog_installed = "mezzanine.blog" in settings.INSTALLED_APPS
-if blog_installed:
-    from mezzanine.blog.models import BlogPost
+if blog_installed():
+    from mezzanine.blog import get_post_model
+    BlogPost = get_post_model()
 
 
 class DisplayableSitemap(Sitemap):