Treat leading-zero slugs as numeric conflicts (#1046)

Previously, numeric detection parsed the slug as an integer and compared the result, causing values such as `00123` to be treated as non-numeric. The check now matches ASCII digits directly.

Includes a regression test for leading-zero numeric slugs. (I ran into this issue when an international phone number was accidentally use as a slug)

Author: fschwahn

Changelog.md

@@ -3,6 +3,10 @@
 We would like to think our many [contributors](https://github.com/norman/friendly_id/graphs/contributors) for
 suggestions, ideas and improvements to FriendlyId.
 
+## Unreleased
+
+* Fix: Treat leading-zero slugs as numeric conflicts. ([#1046](https://github.com/norman/friendly_id/pull/1046))
+
 ## 5.6.0 (2025-12-07)
 
 * Add: `treat_numeric_as_conflict` option to prevent ambiguous numeric slugs. ([#1037](https://github.com/norman/friendly_id/pull/1037))

lib/friendly_id/slug_generator.rb

@@ -28,11 +28,8 @@ def generate(candidates)
 
     def purely_numeric_slug?(slug)
       return false unless slug
-      begin
-        Integer(slug, 10).to_s == slug.to_s
-      rescue ArgumentError, TypeError
-        false
-      end
+
+      slug.to_s.match?(/\A[0-9]+\z/)
     end
   end
 end

test/numeric_slug_test.rb

@@ -2,12 +2,14 @@
 
 class Article < ActiveRecord::Base
   extend FriendlyId
+
   friendly_id :name, use: :slugged
 end
 
 class ArticleWithNumericPrevention < ActiveRecord::Base
   self.table_name = "articles"
   extend FriendlyId
+
   friendly_id :name, use: :slugged
   friendly_id_config.treat_numeric_as_conflict = true
 end
@@ -71,6 +73,14 @@ def model_class
     end
   end
 
+  test "should handle numbers with leading zeroes as numeric when treat_numeric_as_conflict is enabled" do
+    transaction do
+      record = ArticleWithNumericPrevention.create! name: "00123"
+      refute_equal "00123", record.slug
+      assert_match(/\A00123-[0-9a-f-]{36}\z/, record.slug)
+    end
+  end
+
   test "should handle large numbers as numeric when treat_numeric_as_conflict is enabled" do
     transaction do
       record = ArticleWithNumericPrevention.create! name: "999999999"