Add a can_choose_root flag to PageChooserBlock

docs/topics/streamfield.rst

@@ -188,7 +188,13 @@ PageChooserBlock
 
 ``wagtail.wagtailcore.blocks.PageChooserBlock``
 
-A control for selecting a page object, using Wagtail's page browser. The keyword argument ``required`` is accepted.
+A control for selecting a page object, using Wagtail's page browser. The following keyword arguments are accepted:
+
+``required`` (default: True)
+  If true, the field cannot be left blank.
+
+``can_choose_root`` (default: False)
+  If true, the editor can choose the tree root as a page. Normally this would be undesirable, since the tree root is never a usable page, but in some specialised cases it may be appropriate; for example, a block providing a feed of related articles could use a PageChooserBlock to select which subsection articles will be taken from, with the root corresponding to 'everywhere'.
 
 DocumentChooserBlock
 ~~~~~~~~~~~~~~~~~~~~

wagtail/wagtailcore/blocks/field_block.py

@@ -366,6 +366,10 @@ class ChooserBlock(FieldBlock):
 
 
 class PageChooserBlock(ChooserBlock):
+    def __init__(self, can_choose_root=False, **kwargs):
+        self.can_choose_root = can_choose_root
+        super(PageChooserBlock, self).__init__(**kwargs)
+
     @cached_property
     def target_model(self):
         from wagtail.wagtailcore.models import Page  # TODO: allow limiting to specific page types
@@ -374,7 +378,7 @@ class PageChooserBlock(ChooserBlock):
     @cached_property
     def widget(self):
         from wagtail.wagtailadmin.widgets import AdminPageChooser
-        return AdminPageChooser
+        return AdminPageChooser(can_choose_root=self.can_choose_root)
 
     def render_basic(self, value):
         if value:

wagtail/wagtailcore/tests/test_blocks.py

@@ -1302,6 +1302,7 @@ class TestPageChooserBlock(TestCase):
 
         empty_form_html = block.render_form(None, 'page')
         self.assertIn('<input id="page" name="page" placeholder="" type="hidden" />', empty_form_html)
+        self.assertIn('createPageChooser("page", ["wagtailcore.page"], null, false);', empty_form_html)
 
         christmas_page = Page.objects.get(slug='christmas')
         christmas_form_html = block.render_form(christmas_page, 'page')
@@ -1309,6 +1310,11 @@ class TestPageChooserBlock(TestCase):
         self.assertIn(expected_html, christmas_form_html)
         self.assertIn("pick a page, any page", christmas_form_html)
 
+    def test_form_render_with_can_choose_root(self):
+        block = blocks.PageChooserBlock(help_text="pick a page, any page", can_choose_root=True)
+        empty_form_html = block.render_form(None, 'page')
+        self.assertIn('createPageChooser("page", ["wagtailcore.page"], null, true);', empty_form_html)
+
     def test_form_response(self):
         block = blocks.PageChooserBlock()
         christmas_page = Page.objects.get(slug='christmas')