FIX: Push category hashtag slug match to top (#19174)

When searching for categories it is possible for
a child category to have a slug that matches the term
exactly, but will not be found by .lookup since we
don't return these categories unless the ref matches
parent:child.

Introduces a search_sort method to each hashtag data
source so they can provide their custom sort logic of
results, in category's case putting all matching slugs
to the top regardless of parent/child relationship
then sorting by text.

app/services/category_hashtag_data_source.rb

@@ -9,8 +9,7 @@ class CategoryHashtagDataSource
   end
 
   def self.category_to_hashtag_item(guardian_categories, category)
-    category =
-      Category.new(category.slice(:id, :slug, :name, :parent_category_id, :description))
+    category = Category.new(category.slice(:id, :slug, :name, :parent_category_id, :description))
 
     HashtagAutocompleteService::HashtagItem.new.tap do |item|
       item.text = category.name
@@ -51,4 +50,13 @@ class CategoryHashtagDataSource
       .take(limit)
       .map { |category| category_to_hashtag_item(guardian_categories, category) }
   end
+
+  def self.search_sort(search_results, term)
+    search_results
+      .select { |item| item.slug == term }
+      .sort_by { |item| item.text.downcase }
+      .concat(
+        search_results.select { |item| item.slug != term }.sort_by { |item| item.text.downcase },
+      )
+  end
 end

app/services/hashtag_autocomplete_service.rb

@@ -197,11 +197,12 @@ class HashtagAutocompleteService
       next if !all_data_items_valid?(search_results)
 
       search_results =
-        search_results
-          .reject do |item|
+        @@data_sources[type].search_sort(
+          search_results.reject do |item|
             limited_results.any? { |exact| exact.type == type && exact.slug === item.slug }
-          end
-          .sort_by { |item| item.text.downcase }
+          end,
+          term,
+        )
 
       top_ranked_type = type if top_ranked_type.nil?
       limited_results.concat(search_results)

app/services/tag_hashtag_data_source.rb

@@ -51,4 +51,8 @@ class TagHashtagDataSource
       .take(limit)
       .map { |tag| tag_to_hashtag_item(tag, include_count: true) }
   end
+
+  def self.search_sort(search_results, _)
+    search_results.sort_by { |result| result.text.downcase }
+  end
 end

plugins/chat/lib/chat_channel_hashtag_data_source.rb

@@ -40,4 +40,8 @@ class Chat::ChatChannelHashtagDataSource
       []
     end
   end
+
+  def self.search_sort(search_results, _)
+    search_results.sort_by { |result| result.text.downcase }
+  end
 end

spec/services/hashtag_autocomplete_service_spec.rb

@@ -43,6 +43,10 @@ RSpec.describe HashtagAutocompleteService do
           end
         end
     end
+
+    def self.search_sort(search_results, _)
+      search_results.sort_by { |item| item.text.downcase }
+    end
   end
 
   describe ".contexts_with_ordered_types" do
@@ -166,6 +170,37 @@ RSpec.describe HashtagAutocompleteService do
       )
     end
 
+    it "orders categories by exact match on slug (ignoring parent/child distinction) then name, and then name for everything else" do
+      category2 = Fabricate(:category, name: "Book Library", slug: "book-library")
+      Fabricate(:category, name: "Horror", slug: "book", parent_category: category2)
+      Fabricate(:category, name: "Romance", slug: "romance-books")
+      Fabricate(:category, name: "Abstract Philosophy", slug: "abstract-philosophy-books")
+      category6 = Fabricate(:category, name: "Book Reviews", slug: "book-reviews")
+      Fabricate(:category, name: "Good Books", slug: "book", parent_category: category6)
+      expect(subject.search("book", %w[category]).map(&:ref)).to eq(
+        %w[
+          book-reviews:book
+          book-library:book
+          abstract-philosophy-books
+          book-club
+          book-library
+          book-reviews
+          romance-books
+        ],
+      )
+      expect(subject.search("book", %w[category]).map(&:text)).to eq(
+        [
+          "Good Books",
+          "Horror",
+          "Abstract Philosophy",
+          "Book Club",
+          "Book Library",
+          "Book Reviews",
+          "Romance",
+        ],
+      )
+    end
+
     context "when multiple tags and categories are returned" do
       fab!(:category2) { Fabricate(:category, name: "Book Zone", slug: "book-zone") }
       fab!(:category3) { Fabricate(:category, name: "Book Dome", slug: "book-dome") }