New experimental feature branch: subsections.

Despite the name, the idea is to allow reusable apps to add any kind of
formset to the edit page. The first test case is to allow madebyjane to
upload multiple images to a section.

Work in progress.

cms/forms.py

@@ -2,7 +2,6 @@ import swapper
 from django import forms
 from django.contrib.contenttypes.models import ContentType
 from django.core.mail import EmailMessage
-from django.forms import inlineformset_factory
 from django.utils.translation import gettext_lazy as _
 
 Page = swapper.load_model('cms', 'Page')
@@ -80,4 +79,62 @@ class SectionForm(forms.ModelForm):
     # ignored entirely. Workaround to force a ChoiceField anyway:
     type = forms.ChoiceField()
 
-SectionFormSet = inlineformset_factory(Page, Section, form=SectionForm, extra=1)
+
+
+#SectionFormSet = inlineformset_factory(Page, Section, form=SectionForm, extra=1)
+
+def get_view(section):
+    if section:
+        return section.__class__.view_class()
+
+class BaseSectionFormSet(forms.BaseInlineFormSet):
+    '''Potentially nested formset based on
+    https://www.yergler.net/2013/09/03/nested-formsets-redux/
+
+    If a Section subclass provides a 'formset_class' attribute, the
+    section form generated for the edit page will be given a 'formset'
+    attribute. This way, sections can customize their edit form to
+    request additional information.
+
+    Typical usecases could be:
+    - an images section that displays multiple images
+    - a column section that displays separate colums
+    - a calendar section that displays calendar events
+    - etc...
+
+    '''
+    def add_fields(self, form, index):
+        super().add_fields(form, index)
+        section = form.instance
+        view = get_view(section)
+        if hasattr(view, 'formset_class'):
+            form.formset = view.formset_class(
+                instance=section,
+                data=form.data if self.is_bound else None,
+                files=form.files if self.is_bound else None,
+                prefix=f'{form.prefix}-{view.formset_class.get_default_prefix()}')
+            #raise ValueError(form.formset)
+
+
+    def is_valid(self):
+        result = super().is_valid()
+        if self.is_bound:
+            for form in self.forms:
+                if hasattr(form, 'formset'):
+                    result = result and form.formset.is_valid()
+        return result
+
+    def save(self, commit=True):
+        result = super().save(commit=commit)
+        for form in self:
+            if hasattr(form, 'formset'):
+                form.formset.save(commit=commit)
+        return result
+
+SectionFormSet = forms.inlineformset_factory(
+    parent_model = Page,
+    model = Section,
+    form = SectionForm,
+    formset = BaseSectionFormSet,
+    extra=1,
+)

cms/templates/cms/edit.html

@@ -53,6 +53,21 @@
                     {% endif %}
                   {% endfor %}
                 </div>
+
+                {{form.formset.management_form}}
+                {% for form in form.formset %}
+                  <div class="anothersubform" style="padding: 10px; border:2px dotted black;margin-bottom: 10px">
+                    {% for field in form.visible_fields %}
+                      {% if field.name == 'DELETE' and not form.instance.pk %}
+                        
+                      {% elif field.field.widget.input_type == 'checkbox' %}
+                        {% include 'cms/formfield_checkbox.html' with field=field counter=forloop.parentloop.counter0 %}
+                      {% else %}
+                        {% include 'cms/formfield.html' with field=field counter=forloop.parentloop.counter0 %}
+                      {% endif %}
+                    {% endfor %}
+                  </div>
+                {% endfor %}
               </div>
             </section>
           </div>

cms/views.py

@@ -62,6 +62,9 @@ class SectionFormSetView(SectionView):
             kwargs['formset'] = self.get_formset()
         return super().get_context_data(**kwargs)
 
+def get_view(section):
+    return section.__class__.view_class()
+
 class PageView(detail.DetailView):
     '''View of a page with heterogeneous (polymorphic) sections'''
     model = Page
@@ -72,7 +75,7 @@ class PageView(detail.DetailView):
         super().setup(*args, slug=slug, **kwargs)
 
     def initialize_section(self, section):
-        section.view = section.__class__.view_class()
+        section.view = get_view(section)
         section.view.setup(self.request, section)
         section.context = section.view.get_context_data(
             request = self.request,