Allow to filter by borrower in item admin listing view

hardware_provisioning/admin.py

@@ -114,6 +114,34 @@ class AddLoanInline(admin.StackedInline):
         return False
 
 
+class BorrowerFilter(admin.SimpleListFilter):
+    title = 'détenteur actuel'
+    parameter_name = 'user'
+
+    def _filter_loans(self, items_queryset, user_pk=None):
+        qs = Loan.objects.running().filter(item__in=items_queryset)
+        if user_pk is not None:
+            qs.filter(user=user_pk)
+        return qs
+
+    def lookups(self, request, model_admin):
+        # Get relevant (and authorized) users only
+        relevant_items = model_admin.get_queryset(request)
+        users = set()
+        for loan in self._filter_loans(relevant_items):
+            users.add((loan.user.pk, loan.user))
+        return users
+
+    def queryset(self, request, queryset):
+        if self.value():
+            loans_qs = self._filter_loans(queryset).filter(
+                user__pk=self.value(),
+            )
+            return queryset.filter(loans__in=loans_qs)
+        else:
+            return queryset
+
+
 @admin.register(Item)
 class ItemAdmin(admin.ModelAdmin):
     list_display = (
@@ -125,7 +153,7 @@ class ItemAdmin(admin.ModelAdmin):
     )
     list_filter = (
         AvailabilityFilter, 'type', 'storage',
-        'buy_date', OwnerFilter)
+        'buy_date', BorrowerFilter, OwnerFilter)
     search_fields = (
         'designation', 'mac_address', 'serial',
         'owner__email', 'owner__nickname',