FIX: tag input should not include tags you've already chosen in the search results

lib/discourse_tagging.rb

@@ -32,9 +32,13 @@ module DiscourseTagging
 
         # guardian is explicitly nil cause we don't want to strip all
         # staff tags that already passed validation
-        tags = filter_allowed_tags(Tag.where(name: tag_names), nil,           for_input: true,
-                                                                              category: category,
-                                                                              selected_tags: tag_names).to_a
+        tags = filter_allowed_tags(
+          Tag.where(name: tag_names),
+          nil, # guardian
+          for_topic: true,
+          category: category,
+          selected_tags: tag_names
+        ).to_a
 
         if tags.size < tag_names.size && (category.nil? || category.tags.count == 0)
           tag_names.each do |name|
@@ -57,13 +61,22 @@ module DiscourseTagging
   #   term: a search term to filter tags by name
   #   category: a Category to which the object being tagged belongs
   #   for_input: result is for an input field, so only show permitted tags
+  #   for_topic: results are for tagging a topic
   #   selected_tags: an array of tag names that are in the current selection
   def self.filter_allowed_tags(query, guardian, opts = {})
+
+    selected_tag_ids = opts[:selected_tags] ? Tag.where(name: opts[:selected_tags]).pluck(:id) : []
+
+    if opts[:for_input] && !selected_tag_ids.empty?
+      query = query.where('tags.id NOT IN (?)', selected_tag_ids)
+    end
+
     term = opts[:term]
     if term.present?
       term.gsub!("_", "\\_")
       term = clean_tag(term)
       query = query.where('tags.name like ?', "%#{term}%")
+      # query = query.where('tags.id NOT IN (?)', selected_tag_ids) unless selected_tag_ids.empty?
     end
 
     # Filters for category-specific tags:
@@ -86,7 +99,7 @@ module DiscourseTagging
 
         query = query.where("tags.id IN (SELECT tag_id FROM tag_group_memberships WHERE tag_group_id IN (?))", tag_group_ids)
       end
-    elsif opts[:for_input] || category
+    elsif opts[:for_input] || opts[:for_topic] || category
       # exclude tags that are restricted to other categories
       if CategoryTag.exists?
         query = query.where("tags.id NOT IN (SELECT tag_id FROM category_tags)")
@@ -98,9 +111,7 @@ module DiscourseTagging
       end
     end
 
-    if opts[:for_input]
-      selected_tag_ids = opts[:selected_tags] ? Tag.where(name: opts[:selected_tags]).pluck(:id) : []
-
+    if opts[:for_input] || opts[:for_topic]
       unless guardian.nil? || guardian.is_staff?
         staff_tag_names = SiteSetting.staff_tags.split("|")
         query = query.where('tags.name NOT IN (?)', staff_tag_names) if staff_tag_names.present?