Reduce modeladmin’s dependency on wagtail.wagtailimages and wagtail.wagtaildocs

- Remove imports at the top of options.py and views.py that result in ImportError when those apps aren’t installed
- Alter ThumbnailMixin and InspectView to use the `wagtail.wagtailimages.shortcuts.get_rendition_or_not_found()` method to render images, which handles missing image source files gracefully, and reduces code duplication.
- Simplify `get_field_display_value()` by not limiting image and document rendering to ForeignKey fields. It should work consistently for property methods or other attributes too.

CHANGELOG.txt

@@ -24,6 +24,7 @@ Changelog
  * Fix: Choosing a popular search term for promoted search results now works correctly after pagination (Janneke Janssen)
  * Fix: IDs used in tabbed interfaces are now namespaced to avoid collisions with other page elements (Janneke Janssen)
  * Fix: Page title not displaying page name when moving a page (Trent Holliday)
+ * Fix: The ModelAdmin module can now work without the wagtailimages and wagtaildocs apps installed (Andy Babic)
 
 
 1.9 (16.02.2017)

docs/reference/contrib/modeladmin/inspectview.rst

@@ -28,16 +28,19 @@ class:
 ------------------------------------------
 
 **Expected value:** A list or tuple, where each item is the name of a field
-that you'd like ``InpectView`` to render.
+or attribute on the instance that you'd like ``InpectView`` to render.
 
 A sensible value will be rendered for most field types.
 
-If a field happens to be a ``ForeignKey`` linking to the
-``wagtailimages.Image`` model, a thumbnail of that image will be rendered.
-
-If a field happens to be a ``ForeignKey`` linking to the
-``wagtaildocs.Document`` model, a link to that document will be rendered.
+If you have ``wagtail.wagtailimages`` installed, and the value happens to be an
+instance of ``wagtailimages.models.Image`` (or a custom model that subclasses
+``wagtailimages.models.AbstractImage``), a thumbnail of that image will be
+rendered.
 
+If you have `wagtail.wagtaildocs` installed, and the value happens to be an
+instance of `wagtaildocs.models.Document` (or a custom model that subclasses
+``wagtaildocs.models.AbstractDocument``), a link to that document will be
+rendered, along with the document title, file extension and size.
 
 .. _modeladmin_inspect_view_fields_exclude:
 

docs/releases/1.10.rst

@@ -38,6 +38,7 @@ Bug fixes
  * Choosing a popular search term for promoted search results now works correctly after pagination (Janneke Janssen)
  * IDs used in tabbed interfaces are now namespaced to avoid collisions with other page elements (Janneke Janssen)
  * Page title not displaying page name when moving a page (Trent Holliday)
+ * The ModelAdmin module can now work without the wagtailimages and wagtaildocs apps installed (Andy Babic)
 
 
 Upgrade considerations

wagtail/contrib/modeladmin/options.py

@@ -1,5 +1,6 @@
 from __future__ import absolute_import, unicode_literals
 
+from django.conf import settings
 from django.conf.urls import url
 from django.contrib.auth.models import Permission
 from django.core.exceptions import ImproperlyConfigured
@@ -10,7 +11,6 @@ from django.utils.translation import ugettext_lazy as _
 
 from wagtail.wagtailcore import hooks
 from wagtail.wagtailcore.models import Page
-from wagtail.wagtailimages.models import Filter
 
 from .helpers import (
     AdminURLHelper, ButtonHelper, PageAdminURLHelper, PageButtonHelper, PagePermissionHelper,
@@ -72,6 +72,14 @@ class ThumbnailMixin(object):
     thumb_col_header_text = _('image')
     thumb_default = None
 
+    def __init__(self, *args, **kwargs):
+        if 'wagtail.wagtailimages' not in settings.INSTALLED_APPS:
+            raise ImproperlyConfigured(
+                u"The `wagtail.wagtailimages` app must be installed in order "
+                "to use the `ThumbnailMixin` class."
+            )
+        super(ThumbnailMixin, self).__init__(*args, **kwargs)
+
     def admin_thumb(self, obj):
         try:
             image = getattr(obj, self.thumb_image_field_name, None)
@@ -86,13 +94,17 @@ class ThumbnailMixin(object):
             'width': self.thumb_image_width,
             'class': self.thumb_classname,
         }
-        if image:
-            fltr = Filter(spec=self.thumb_image_filter_spec)
-            img_attrs.update({'src': image.get_rendition(fltr).url})
-            return mark_safe('<img{}>'.format(flatatt(img_attrs)))
-        elif self.thumb_default:
-            return mark_safe('<img{}>'.format(flatatt(img_attrs)))
-        return ''
+        if not image:
+            if self.thumb_default:
+                return mark_safe('<img{}>'.format(flatatt(img_attrs)))
+            return ''
+
+        # try to get a rendition of the image to use
+        from wagtail.wagtailimages.shortcuts import get_rendition_or_not_found
+        spec = self.thumb_image_filter_spec
+        rendition = get_rendition_or_not_found(image, spec)
+        img_attrs.update({'src': rendition.url})
+        return mark_safe('<img{}>'.format(flatatt(img_attrs)))
     admin_thumb.short_description = thumb_col_header_text
 
 

wagtail/contrib/modeladmin/views.py

@@ -35,9 +35,6 @@ from django.views.generic.edit import FormView
 from wagtail.wagtailadmin import messages
 from wagtail.wagtailadmin.edit_handlers import (
     ObjectList, extract_panel_definitions_from_model_class)
-from wagtail.wagtaildocs.models import get_document_model
-from wagtail.wagtailimages import get_image_model
-from wagtail.wagtailimages.models import Filter
 
 from .forms import ParentChooserForm
 
@@ -850,7 +847,7 @@ class InspectView(InstanceSpecificView):
         return label
 
     def get_field_display_value(self, field_name, field=None):
-        """ Return a display value for a field """
+        """ Return a display value for a field/attribute """
 
         # First we check for a 'get_fieldname_display' property/method on
         # the model, and return the value of that, if present.
@@ -860,39 +857,37 @@ class InspectView(InstanceSpecificView):
                 return val_funct()
             return val_funct
 
-        # If we have a real field, we can utilise that to try to display
-        # something more useful
-        if field is not None:
-            try:
-                field_type = field.get_internal_type()
-                if (
-                    field_type == 'ForeignKey' and
-                    field.related_model == get_image_model()
-                ):
-                    # The field is an image
-                    return self.get_image_field_display(field_name, field)
+        # Now let's get the attribute value from the instance itself and see if
+        # we can render something useful. raises AttributeError appropriately.
+        val = getattr(self.instance, field_name)
 
-                if (
-                    field_type == 'ForeignKey' and
-                    field.related_model == get_document_model()
-                ):
-                    # The field is a document
-                    return self.get_document_field_display(field_name, field)
+        # wagtail.wagtailimages might not be installed
+        try:
+            from wagtail.wagtailimages.models import AbstractImage
+            if isinstance(val, AbstractImage):
+                # Render a rendition of the image
+                return self.get_image_field_display(field_name, field)
+        except RuntimeError:
+            pass
 
-            except AttributeError:
-                pass
+        # wagtail.wagtaildocuments might not be installed
+        try:
+            from wagtail.wagtaildocs.models import AbstractDocument
+            if isinstance(val, AbstractDocument):
+                # Render a link to the document
+                return self.get_document_field_display(field_name, field)
+        except RuntimeError:
+            pass
 
-        # Resort to getting the value of 'field_name' from the instance
-        return getattr(self.instance, field_name,
-                       self.model_admin.get_empty_value_display(field_name))
+        # Resort to returning the real value or 'empty value'
+        return val or self.model_admin.get_empty_value_display(field_name)
 
     def get_image_field_display(self, field_name, field):
         """ Render an image """
+        from wagtail.wagtailimages.shortcuts import get_rendition_or_not_found
         image = getattr(self.instance, field_name)
         if image:
-            fltr = Filter(spec='max-400x400')
-            rendition = image.get_rendition(fltr)
-            return rendition.img_tag
+            return get_rendition_or_not_found(image, 'max-400x400').img_tag
         return self.model_admin.get_empty_value_display(field_name)
 
     def get_document_field_display(self, field_name, field):