Add ASCII slug for topic function

lib/discourse_modifications/topic_slug.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+require 'any_ascii'
+
+module ::DiscourseModifications
+  class TopicSlug
+
+    # Converts a topic title into a slug, removing any emoji strings and normalizing the text.
+    # This is primarily adds the unicode normalization step to the existing slug generation process
+    # for ASCII encoding.
+    def self.slug_for_topic(topic, slug, title)
+      return slug unless (SiteSetting.slug_generation_method || :ascii).to_sym == :ascii
+
+      string = title.gsub(/:([\w\-+]+(?::t\d)?):/, "")
+      string = AnyAscii.transliterate(string)
+      string = Slug.ascii_generator(string)
+      string = Slug.prettify_slug(string, max_length: Slug::MAX_LENGTH)
+
+      string.blank? || Slug.slug_is_only_numbers?(string) ? "topic-#{topic.id}" : string
+    end
+  end
+end

plugin.rb

@@ -8,6 +8,8 @@
 # url: TODO
 # required_version: 2.7.0
 
+gem 'any_ascii', '0.3.2'
+
 enabled_site_setting :discourse_modifications_enabled
 
 module ::DiscourseModifications
@@ -18,4 +20,9 @@ module ::DiscourseModifications
 
 after_initialize do
   # Code which should run after Rails has finished booting
+
+  # Note: if this file gets too large, consider moving code into separate files in the lib directory
+  # and applying a Initializer pattern to load them.
+
+  Topic.slug_computed_callbacks << ::DiscourseModifications::TopicSlug.method(:slug_for_topic)
 end

spec/lib/discourse_modifications/topic_slug_spec.rb

@@ -0,0 +1,62 @@
+# frozen_string_literal: true
+
+RSpec.configure { |c| c.filter_run_when_matching :focus }
+
+RSpec.describe DiscourseModifications::TopicSlug do
+  let(:topic) { Fabricate(:topic, id: 42) }
+
+  describe ".slug_for_topic" do
+    before do
+      # Default to ascii slug generation
+      allow(SiteSetting).to receive(:slug_generation_method).and_return("ascii")
+    end
+
+    it "removes emoji codes from the title" do
+      title = "Hello :smile: World"
+      slug = "hello-world"
+      expect(described_class.slug_for_topic(topic, slug, title)).to eq("hello-world")
+    end
+
+    it "unicode normalizes the title" do
+      title = "Café"
+      slug = "cafe"
+      expect(described_class.slug_for_topic(topic, slug, title)).to eq("cafe")
+    end
+
+    it "returns the original slug if slug_generation_method is not ascii" do
+      allow(SiteSetting).to receive(:slug_generation_method).and_return("encoded")
+      expect(described_class.slug_for_topic(topic, "original-slug", "Some Title")).to eq("original-slug")
+    end
+
+    it "returns a fallback slug if the result is blank" do
+      title = ":smile:"
+      slug = ""
+      expect(described_class.slug_for_topic(topic, slug, title)).to eq("topic-42")
+    end
+
+    it "returns a fallback slug if the result is only numbers" do
+      title = "123456"
+      slug = "123456"
+      expect(described_class.slug_for_topic(topic, slug, title)).to eq("topic-42")
+    end
+
+    it "truncates the slug to the max length" do
+      long_title = "a" * (Slug::MAX_LENGTH + 10)
+      slug = "a" * (Slug::MAX_LENGTH + 10)
+      result = described_class.slug_for_topic(topic, slug, long_title)
+      expect(result.length).to eq(Slug::MAX_LENGTH)
+    end
+
+    it "handles titles with multiple emoji codes" do
+      title = "Hello :smile: World :rocket:"
+      slug = "hello-world"
+      expect(described_class.slug_for_topic(topic, slug, title)).to eq("hello-world")
+    end
+
+    it "handles titles with emoji codes with t modifier" do
+      title = "Hello :wave:t2: World"
+      slug = "hello-world"
+      expect(described_class.slug_for_topic(topic, slug, title)).to eq("hello-world")
+    end
+  end
+end