Build up the filter form with mixins, so that we can reuse the collection filter code

wagtail/admin/forms/choosers.py

@@ -44,3 +44,35 @@ class EmailLinkChooserForm(forms.Form):
 class PhoneLinkChooserForm(forms.Form):
     phone_number = forms.CharField(required=True)
     link_text = forms.CharField(required=False)
+
+
+class SearchFilterMixin(forms.Form):
+    """
+    Mixin for a chooser listing filter form, to provide a search field
+    """
+
+    q = forms.CharField(
+        label=_("Search term"),
+        widget=forms.TextInput(attrs={"placeholder": _("Search")}),
+        required=False,
+    )
+
+
+class CollectionFilterMixin(forms.Form):
+    """
+    Mixin for a chooser listing filter form, to provide a collection filter field.
+    The view must pass a `collections` keyword argument when constructing the form
+    """
+
+    def __init__(self, *args, collections=None, **kwargs):
+        super().__init__(*args, **kwargs)
+
+        if collections:
+            collection_choices = [
+                ("", _("All collections"))
+            ] + collections.get_indented_choices()
+            self.fields["collection_id"] = forms.ChoiceField(
+                label=_("Collection"),
+                choices=collection_choices,
+                required=False,
+            )

wagtail/admin/views/generic/chooser.py

@@ -15,8 +15,10 @@ from django.utils.translation import gettext_lazy as _
 from django.views.generic.base import ContextMixin, View
 
 from wagtail.admin.admin_url_finder import AdminURLFinder
+from wagtail.admin.forms.choosers import CollectionFilterMixin, SearchFilterMixin
 from wagtail.admin.modal_workflow import render_modal_workflow
 from wagtail.admin.ui.tables import Table, TitleColumn
+from wagtail.models import CollectionMember
 from wagtail.permission_policies import BlanketPermissionPolicy, ModelPermissionPolicy
 from wagtail.search.backends import get_search_backend
 from wagtail.search.index import class_is_indexed
@@ -73,16 +75,16 @@ class BaseChooseView(ModalPageFurnitureMixin, ContextMixin, View):
         if self.filter_form_class:
             return self.filter_form_class
         else:
-            fields = {}
+            bases = [forms.Form]
             if class_is_indexed(self.model):
-                fields["q"] = forms.CharField(
-                    label=_("Search term"), widget=forms.TextInput(), required=False
-                )
+                bases.insert(0, SearchFilterMixin)
+            if issubclass(self.model, CollectionMember):
+                bases.insert(0, CollectionFilterMixin)
 
             return type(
                 "FilterForm",
-                (forms.Form,),
-                fields,
+                tuple(bases),
+                {},
             )
 
     def get_filter_form(self):

wagtail/documents/views/chooser.py

@@ -66,30 +66,8 @@ class DownloadColumn(Column):
         return context
 
 
-class DocumentFilterForm(forms.Form):
-    q = forms.CharField(
-        label=_("Search term"),
-        widget=forms.TextInput(attrs={"placeholder": _("Search")}),
-        required=False,
-    )
-
-    def __init__(self, *args, collections, **kwargs):
-        super().__init__(*args, **kwargs)
-
-        if collections:
-            collection_choices = [
-                ("", _("All collections"))
-            ] + collections.get_indented_choices()
-            self.fields["collection_id"] = forms.ChoiceField(
-                label=_("Collection"),
-                choices=collection_choices,
-                required=False,
-            )
-
-
 class BaseDocumentChooseView(BaseChooseView):
     results_template_name = "wagtaildocs/chooser/results.html"
-    filter_form_class = DocumentFilterForm
     per_page = 10
 
     def get_object_list(self):

wagtail/images/views/chooser.py

@@ -1,4 +1,3 @@
-from django import forms
 from django.conf import settings
 from django.shortcuts import get_object_or_404
 from django.template.loader import render_to_string
@@ -45,27 +44,6 @@ class ImageChosenResponseMixin(ChosenResponseMixin):
         return response_data
 
 
-class ImageFilterForm(forms.Form):
-    q = forms.CharField(
-        label=_("Search term"),
-        widget=forms.TextInput(attrs={"placeholder": _("Search")}),
-        required=False,
-    )
-
-    def __init__(self, *args, collections, **kwargs):
-        super().__init__(*args, **kwargs)
-
-        if collections:
-            collection_choices = [
-                ("", _("All collections"))
-            ] + collections.get_indented_choices()
-            self.fields["collection_id"] = forms.ChoiceField(
-                label=_("Collection"),
-                choices=collection_choices,
-                required=False,
-            )
-
-
 class ImageCreationFormMixin(CreationFormMixin):
     creation_tab_id = "upload"
     create_url_name = "wagtailimages:chooser_upload"
@@ -102,7 +80,6 @@ class BaseImageChooseView(BaseChooseView):
     results_url_name = "wagtailimages:chooser_results"
     template_name = "wagtailimages/chooser/chooser.html"
     results_template_name = "wagtailimages/chooser/results.html"
-    filter_form_class = ImageFilterForm
     per_page = getattr(settings, "WAGTAILIMAGES_CHOOSER_PAGE_SIZE", 12)
 
     def get_object_list(self):