FEATURE: Sort hashtags starting with term higher priority (#19463)

This introduces another "section" of queries to the
hashtag autocomplete search, which returns results for
each type that start with the search term. So now results
will be in this order, and within these sections ordered
by the types in priority order:

1. Exact matches sorted by type
2. "starts with" sorted by type
3. Everything else sorted by type then name within type

plugins/chat/lib/chat_channel_fetcher.rb

@@ -99,19 +99,19 @@ module Chat::ChatChannelFetcher
     channels = channels.where(status: options[:status]) if options[:status].present?
 
     if options[:filter].present?
-      category_filter = \
-        if options[:filter_on_category_name]
-          "OR categories.name ILIKE :filter"
-        else
-          ""
-        end
+      category_filter =
+        (options[:filter_on_category_name] ? "OR categories.name ILIKE :filter" : "")
 
       sql =
         "chat_channels.name ILIKE :filter OR chat_channels.slug ILIKE :filter #{category_filter}"
+      if options[:match_filter_on_starts_with]
+        filter_sql = "#{options[:filter].downcase}%"
+      else
+        filter_sql = "%#{options[:filter].downcase}%"
+      end
+
       channels =
-        channels.where(sql, filter: "%#{options[:filter].downcase}%").order(
-          "chat_channels.name ASC, categories.name ASC",
-        )
+        channels.where(sql, filter: filter_sql).order("chat_channels.name ASC, categories.name ASC")
     end
 
     if options.key?(:slugs)

plugins/chat/lib/chat_channel_hashtag_data_source.rb

@@ -27,7 +27,12 @@ class Chat::ChatChannelHashtagDataSource
     end
   end
 
-  def self.search(guardian, term, limit)
+  def self.search(
+    guardian,
+    term,
+    limit,
+    condition = HashtagAutocompleteService.search_conditions[:contains]
+  )
     if SiteSetting.enable_experimental_hashtag_autocomplete
       return [] if !guardian.can_chat?
       Chat::ChatChannelFetcher
@@ -36,6 +41,8 @@ class Chat::ChatChannelHashtagDataSource
           filter: term,
           limit: limit,
           exclude_dm_channels: true,
+          match_filter_on_starts_with:
+            condition == HashtagAutocompleteService.search_conditions[:starts_with],
         )
         .map { |channel| channel_to_hashtag_item(guardian, channel) }
     else