Fix next_cursor/previous_cursor for empty pages

.rubocop.yml

@@ -21,6 +21,9 @@ Style/SymbolArray:
 Style/IfUnlessModifier:
   Enabled: false
 
+Style/GuardClause:
+  Enabled: false
+
 Layout/EmptyLinesAroundAccessModifier:
   EnforcedStyle: only_before
 
@@ -53,3 +56,6 @@ Minitest/MultipleAssertions:
 
 Minitest/EmptyLineBeforeAssertionMethods:
   Enabled: false
+
+Minitest/AssertEmptyLiteral:
+  Enabled: false

CHANGELOG.md

@@ -1,5 +1,6 @@
 ## master (unreleased)
 
+- Fix `next_cursor`/`previous_cursor` for empty pages
 - Fix iterating using only a timestamp column
 
 - Add the ability to skip implicitly appending a primary key to the list of sorting columns.

lib/activerecord_cursor_paginate/page.rb

@@ -78,8 +78,10 @@ def cursors
 
     private
       def cursor_for_record(record)
-        cursor = Cursor.from_record(record, columns: @order_columns)
-        cursor.encode
+        if record
+          cursor = Cursor.from_record(record, columns: @order_columns)
+          cursor.encode
+        end
       end
   end
 end

test/paginator_test.rb

@@ -275,4 +275,17 @@ def test_returns_page_object
     assert page2.has_next?
     assert page2.has_previous?
   end
+
+  def test_empty_page
+    p = User.where("created_at > ?", Time.current).cursor_paginate
+    page = p.fetch
+
+    assert_equal([], page.records)
+    assert_equal(0, page.count)
+    assert_nil page.next_cursor
+    assert_nil page.previous_cursor
+    assert_not page.has_previous?
+    assert_not page.has_next?
+    assert_empty page.cursors
+  end
 end