Fixed #18388 - Added InlineModelAdmin.get_max_num hook.

Thanks d.willy.c.c@ for the suggestion and Melevir and Areski Belaid for work
on the patch.

2 files changed, 13 insertions, 2 deletions

diff --git a/tests/admin_inlines/admin.py b/tests/admin_inlines/admin.py
index 2bc9dc5234..2f88248ca4 100644
--- a/tests/admin_inlines/admin.py
+++ b/tests/admin_inlines/admin.py
@@ -129,7 +129,7 @@ class ChildModel1Inline(admin.TabularInline):
 class ChildModel2Inline(admin.StackedInline):
     model = ChildModel2
 
-# admin for #19425
+# admin for #19425 and #18388
 class BinaryTreeAdmin(admin.TabularInline):
     model = BinaryTree
 
@@ -137,9 +137,14 @@ class BinaryTreeAdmin(admin.TabularInline):
         extra = 2
         if obj:
             return extra - obj.binarytree_set.count()
-
         return extra
 
+    def get_max_num(self, request, obj=None, **kwargs):
+        max_num = 3
+        if obj:
+            return max_num - obj.binarytree_set.count()
+        return max_num
+
 # admin for #19524
 class SightingInline(admin.TabularInline):
     model = Sighting
diff --git a/tests/admin_inlines/tests.py b/tests/admin_inlines/tests.py
index 23c7f95bfe..78ccf074d5 100644
--- a/tests/admin_inlines/tests.py
+++ b/tests/admin_inlines/tests.py
@@ -197,12 +197,18 @@ class TestInline(TestCase):
         bt_head = BinaryTree.objects.create(name="Tree Head")
         bt_child = BinaryTree.objects.create(name="First Child", parent=bt_head)
 
+        # The maximum number of forms should respect 'get_max_num' on the
+        # ModelAdmin
+        max_forms_input = '<input id="id_binarytree_set-MAX_NUM_FORMS" name="binarytree_set-MAX_NUM_FORMS" type="hidden" value="%d" />'
         # The total number of forms will remain the same in either case
         total_forms_hidden = '<input id="id_binarytree_set-TOTAL_FORMS" name="binarytree_set-TOTAL_FORMS" type="hidden" value="2" />'
+
         response = self.client.get('/admin/admin_inlines/binarytree/add/')
+        self.assertContains(response, max_forms_input % 3)
         self.assertContains(response, total_forms_hidden)
 
         response = self.client.get("/admin/admin_inlines/binarytree/%d/" % bt_head.id)
+        self.assertContains(response, max_forms_input % 2)
         self.assertContains(response, total_forms_hidden)