Make custom PageManagers return the correct PageQuerySet subclass

As reported in https://github.com/wagtail/wagtail/issues/3250#issuecomment-284988695, custom page managers created with PageManager.from_queryset(CustomPageQuerySet) fail to return instances of CustomPageQuerySet. This breaks the EventPageQuerySet example given at http://docs.wagtail.io/en/v1.9/topics/pages.html#custom-page-managers.

CHANGELOG.txt

@@ -28,6 +28,7 @@ Changelog
  * Fix: Prevent `USE_THOUSAND_SEPARATOR = True` from breaking the image focal point chooser (Sævar Öfjörð Magnússon)
  * Fix: Removed deprecated `SessionAuthenticationMiddleware` from project template (Samir Shah)
  * Fix: Custom display page titles defined with `get_admin_display_title` are now shown in search results (Ben Sturmfels, Matt Westcott)
+ * Fix: Custom PageManagers now return the correct PageQuerySet subclass (Matt Westcott)
 
 
 1.12.2 (18.09.2017)

docs/releases/1.13.rst

@@ -42,6 +42,7 @@ Bug fixes
  * Prevent ``USE_THOUSAND_SEPARATOR = True`` from breaking the image focal point chooser (Sævar Öfjörð Magnússon)
  * Removed deprecated ``SessionAuthenticationMiddleware`` from project template (Samir Shah)
  * Custom display page titles defined with ``get_admin_display_title`` are now shown in search results (Ben Sturmfels, Matt Westcott)
+ * Custom PageManagers now return the correct PageQuerySet subclass (Matt Westcott)
 
 Upgrade considerations
 ======================

wagtail/tests/testapp/models.py

@@ -28,7 +28,7 @@ from wagtail.wagtailadmin.forms import WagtailAdminPageForm
 from wagtail.wagtailadmin.utils import send_mail
 from wagtail.wagtailcore.blocks import CharBlock, RichTextBlock
 from wagtail.wagtailcore.fields import RichTextField, StreamField
-from wagtail.wagtailcore.models import Orderable, Page, PageManager
+from wagtail.wagtailcore.models import Orderable, Page, PageManager, PageQuerySet
 from wagtail.wagtaildocs.edit_handlers import DocumentChooserPanel
 from wagtail.wagtaildocs.models import AbstractDocument, Document
 from wagtail.wagtailforms.models import AbstractEmailForm, AbstractFormField, AbstractFormSubmission
@@ -851,8 +851,12 @@ class CustomImageFilePath(AbstractImage):
         return os.path.join(folder_name, checksum[:3], filename)
 
 
-class CustomManager(PageManager):
-    pass
+class CustomPageQuerySet(PageQuerySet):
+    def about_spam(self):
+        return self.filter(title__contains='spam')
+
+
+CustomManager = PageManager.from_queryset(CustomPageQuerySet)
 
 
 class CustomManagerPage(Page):

wagtail/wagtailcore/models.py

@@ -195,7 +195,7 @@ def get_default_page_content_type():
 
 class BasePageManager(models.Manager):
     def get_queryset(self):
-        return PageQuerySet(self.model).order_by('path')
+        return self._queryset_class(self.model).order_by('path')
 
 
 PageManager = BasePageManager.from_queryset(PageQuerySet)

wagtail/wagtailcore/tests/test_page_model.py

@@ -17,7 +17,8 @@ from freezegun import freeze_time
 
 from wagtail.tests.testapp.models import (
     AbstractPage, Advert, AlwaysShowInMenusPage, BlogCategory, BlogCategoryBlogPage, BusinessChild,
-    BusinessIndex, BusinessNowherePage, BusinessSubIndex, CustomManager, CustomManagerPage,
+    BusinessIndex, BusinessNowherePage, BusinessSubIndex,
+    CustomManager, CustomManagerPage, CustomPageQuerySet,
     EventIndex, EventPage, GenericSnippetPage, ManyToManyBlogPage, MTIBasePage, MTIChildPage,
     MyCustomPage, OneToOnePage, SimplePage, SingleEventPage, SingletonPage, StandardIndex,
     TaggedPage)
@@ -1267,6 +1268,17 @@ class TestPageManager(TestCase):
         """
         self.assertIs(type(CustomManagerPage.objects), CustomManager)
 
+    def test_custom_page_queryset(self):
+        """
+        Managers that are constructed from a custom PageQuerySet
+        (via PageManager.from_queryset(CustomPageQuerySet)) should return
+        querysets of that type
+        """
+        self.assertIs(type(CustomManagerPage.objects.all()), CustomPageQuerySet)
+        self.assertIs(type(CustomManagerPage.objects.about_spam()), CustomPageQuerySet)
+        self.assertIs(type(CustomManagerPage.objects.all().about_spam()), CustomPageQuerySet)
+        self.assertIs(type(CustomManagerPage.objects.about_spam().all()), CustomPageQuerySet)
+
     def test_abstract_base_page_manager(self):
         """
         Abstract base classes should be able to override their default Manager,