FEATURE: restrict tags to be used in a category

app/assets/javascripts/discourse/components/edit-category-tags.js.es6

@@ -0,0 +1,4 @@
+import { buildCategoryPanel } from 'discourse/components/edit-category-panel';
+
+export default buildCategoryPanel('tags', {
+});

app/assets/javascripts/discourse/components/tag-chooser.js.es6

@@ -6,7 +6,7 @@ function formatTag(t) {
 
 export default Ember.TextField.extend({
   classNameBindings: [':tag-chooser'],
-  attributeBindings: ['tabIndex'],
+  attributeBindings: ['tabIndex', 'placeholderKey', 'categoryId'],
 
   _setupTags: function() {
     const tags = this.get('tags') || [];
@@ -25,7 +25,7 @@ export default Ember.TextField.extend({
 
     this.$().select2({
       tags: true,
-      placeholder: I18n.t('tagging.choose_for_topic'),
+      placeholder: I18n.t(this.get('placeholderKey') || 'tagging.choose_for_topic'),
       maximumInputLength: this.siteSettings.max_tag_length,
       maximumSelectionSize: this.siteSettings.max_tags_per_topic,
       initSelection(element, callback) {
@@ -78,7 +78,7 @@ export default Ember.TextField.extend({
         url: Discourse.getURL("/tags/filter/search"),
         dataType: 'json',
         data: function (term) {
-          return { q: term, limit: self.siteSettings.max_tag_search_results, filterForInput: true };
+          return { q: term, limit: self.siteSettings.max_tag_search_results, filterForInput: true, categoryId: self.get('categoryId') };
         },
         results: function (data) {
           if (self.siteSettings.tags_sort_alphabetically) {

app/assets/javascripts/discourse/models/category.js.es6

@@ -86,7 +86,8 @@ const Category = RestModel.extend({
         allow_badges: this.get('allow_badges'),
         custom_fields: this.get('custom_fields'),
         topic_template: this.get('topic_template'),
-        suppress_from_homepage: this.get('suppress_from_homepage')
+        suppress_from_homepage: this.get('suppress_from_homepage'),
+        allowed_tags: this.get('allowed_tags')
       },
       type: this.get('id') ? 'PUT' : 'POST'
     });

app/assets/javascripts/discourse/templates/components/edit-category-tags.hbs

@@ -0,0 +1,4 @@
+<section class="field">
+  <p>{{i18n 'category.tags_allowed_tags'}}</p>
+  {{tag-chooser placeholderKey="category.tags_placeholder" tags=category.allowed_tags}}
+</section>

app/assets/javascripts/discourse/templates/composer.hbs

@@ -98,7 +98,7 @@
           <div class='submit-panel'>
             {{plugin-outlet "composer-fields-below"}}
             {{#if canEditTags}}
-              {{tag-chooser tags=model.tags tabIndex="4"}}
+              {{tag-chooser tags=model.tags tabIndex="4" categoryId=model.categoryId}}
             {{/if}}
             <button {{action "save"}} tabindex="5" class="btn btn-primary create {{if disableSubmit 'disabled'}}" title="{{i18n 'composer.title'}}">{{{model.saveIcon}}}{{model.saveText}}</button>
             <a href {{action "cancel"}} class='cancel' tabindex="6">{{i18n 'cancel'}}</a>

app/assets/javascripts/discourse/templates/modal/edit-category.hbs

@@ -7,6 +7,9 @@
     {{edit-category-tab panels=panels selectedTab=selectedTab tab="settings"}}
     {{edit-category-tab panels=panels selectedTab=selectedTab tab="images"}}
     {{edit-category-tab panels=panels selectedTab=selectedTab tab="topic-template"}}
+    {{#if siteSettings.tagging_enabled}}
+      {{edit-category-tab panels=panels selectedTab=selectedTab tab="tags"}}
+    {{/if}}
   </ul>
 
   <div class="modal-body">

app/assets/javascripts/discourse/templates/topic.hbs

@@ -25,7 +25,7 @@
 
             {{#if canEditTags}}
               <br>
-              {{tag-chooser tags=buffered.tags}}
+              {{tag-chooser tags=buffered.tags categoryId=buffered.category_id}}
             {{/if}}
 
             {{plugin-outlet "edit-topic"}}

app/controllers/categories_controller.rb

@@ -194,7 +194,8 @@ class CategoriesController < ApplicationController
                         :allow_badges,
                         :topic_template,
                         :custom_fields => [params[:custom_fields].try(:keys)],
-                        :permissions => [*p.try(:keys)])
+                        :permissions => [*p.try(:keys)],
+                        :allowed_tags => [])
       end
     end
 

app/controllers/tags_controller.rb

@@ -104,18 +104,15 @@ class TagsController < ::ApplicationController
   end
 
   def search
-    query = self.class.tags_by_count(guardian, params.slice(:limit))
-    term = params[:q]
-    if term.present?
-      term.gsub!(/[^a-z0-9\.\-\_]*/, '')
-      term.gsub!("_", "\\_")
-      query = query.where('tags.name like ?', "%#{term}%")
-    end
-
-    if params[:filterForInput] && !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?
-    end
+    query = DiscourseTagging.filter_allowed_tags(
+      self.class.tags_by_count(guardian, params.slice(:limit)),
+      guardian,
+      {
+        for_input: params[:filterForInput],
+        term: params[:q],
+        category: params[:categoryId] ? Category.find_by_id(params[:categoryId]) : nil
+      }
+    )
 
     tags = query.count.map {|t, c| { id: t, text: t, count: c } }
 

app/models/category.rb

@@ -55,6 +55,9 @@ class Category < ActiveRecord::Base
   belongs_to :parent_category, class_name: 'Category'
   has_many :subcategories, class_name: 'Category', foreign_key: 'parent_category_id'
 
+  has_many :category_tags
+  has_many :tags, through: :category_tags
+
   scope :latest, ->{ order('topic_count desc') }
 
   scope :secured, ->(guardian = nil) {
@@ -312,6 +315,12 @@ SQL
     end
   end
 
+  def allowed_tags=(tag_names)
+    if self.tags.pluck(:name).sort != tag_names.sort
+      self.tags = Tag.where(name: tag_names).all
+    end
+  end
+
   def downcase_email
     self.email_in = (email_in || "").strip.downcase.presence
   end

app/models/category_tag.rb

@@ -0,0 +1,4 @@
+class CategoryTag < ActiveRecord::Base
+  belongs_to :category
+  belongs_to :tag
+end

app/models/tag.rb

@@ -1,8 +1,13 @@
 class Tag < ActiveRecord::Base
   validates :name, presence: true, uniqueness: true
+
+  has_many :tag_users # notification settings
+
   has_many :topic_tags, dependent: :destroy
   has_many :topics, through: :topic_tags
-  has_many :tag_users
+
+  has_many :category_tags, dependent: :destroy
+  has_many :categories, through: :category_tags
 
   def self.tags_by_count_query(opts={})
     q = TopicTag.joins(:tag, :topic).group("topic_tags.tag_id, tags.name").order('count_all DESC')

app/serializers/category_serializer.rb

@@ -13,7 +13,8 @@ class CategorySerializer < BasicCategorySerializer
              :cannot_delete_reason,
              :is_special,
              :allow_badges,
-             :custom_fields
+             :custom_fields,
+             :allowed_tags
 
   def group_permissions
     @group_permissions ||= begin
@@ -77,4 +78,12 @@ class CategorySerializer < BasicCategorySerializer
      (user && CategoryUser.where(user: user, category: object).first.try(:notification_level))
   end
 
+  def include_allowed_tags?
+    SiteSetting.tagging_enabled
+  end
+
+  def allowed_tags
+    object.tags.pluck(:name)
+  end
+
 end

config/locales/client.en.yml

@@ -1716,6 +1716,9 @@ en:
       general: 'General'
       settings: 'Settings'
       topic_template: "Topic Template"
+      tags: "Tags"
+      tags_allowed_tags: "Tags that can only be used in this category:"
+      tags_placeholder: "(Optional) list of allowed tags"
       delete: 'Delete Category'
       create: 'New Category'
       create_long: 'Create a new category'

db/migrate/20160527191614_create_category_tags.rb

@@ -0,0 +1,12 @@
+class CreateCategoryTags < ActiveRecord::Migration
+  def change
+    create_table :category_tags do |t|
+      t.references :category, null: false
+      t.references :tag,      null: false
+      t.timestamps
+    end
+
+    add_index :category_tags, [:category_id, :tag_id], name: "idx_category_tags_ix1", unique: true
+    add_index :category_tags, [:tag_id, :category_id], name: "idx_category_tags_ix2", unique: true
+  end
+end

lib/discourse_tagging.rb

@@ -32,12 +32,14 @@ module DiscourseTagging
       end
 
       if tag_names.present?
-        tags = Tag.where(name: tag_names).all
-        if tags.size < tag_names.size
-          existing_names = tags.map(&:name)
+        category = topic.category
+        tags = filter_allowed_tags(Tag.where(name: tag_names), guardian, { for_input: true, category: category }).to_a
+
+        if tags.size < tag_names.size && (category.nil? || category.tags.count == 0)
           tag_names.each do |name|
-            next if existing_names.include?(name)
-            tags << Tag.create(name: name)
+            unless Tag.where(name: name).exists?
+              tags << Tag.create(name: name)
+            end
           end
         end
 
@@ -52,6 +54,34 @@ module DiscourseTagging
     true
   end
 
+  # Options:
+  #   term: a search term to filter tags by name
+  #   for_input: result is for an input field, so only show permitted tags
+  #   category: a Category to which the object being tagged belongs
+  def self.filter_allowed_tags(query, guardian, opts={})
+    term = opts[:term]
+    if term.present?
+      term.gsub!(/[^a-z0-9\.\-\_]*/, '')
+      term.gsub!("_", "\\_")
+      query = query.where('tags.name like ?', "%#{term}%")
+    end
+
+    if opts[:for_input]
+      unless 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?
+      end
+
+      if opts[:category] && opts[:category].tags.count > 0
+        query = query.where("tags.id IN (SELECT tag_id FROM category_tags WHERE category_id = ?)", opts[:category].id)
+      elsif CategoryTag.exists?
+        query = query.where("tags.id NOT IN (SELECT tag_id FROM category_tags)")
+      end
+    end
+
+    query
+  end
+
   def self.auto_notify_for(tags, topic)
     TagUser.auto_watch_new_topic(topic, tags)
     TagUser.auto_track_new_topic(topic, tags)
@@ -78,17 +108,16 @@ module DiscourseTagging
 
     return unless tags.present?
 
-    tags.map! {|t| clean_tag(t) }
-    tags.delete_if {|t| t.blank? }
-    tags.uniq!
+    tag_names = tags.map {|t| clean_tag(t) }
+    tag_names.delete_if {|t| t.blank? }
+    tag_names.uniq!
 
     # If the user can't create tags, remove any tags that don't already exist
-    # TODO: this is doing a full count, it should just check first or use a cache
     unless guardian.can_create_tag?
-      tags = Tag.where(name: tags).pluck(:name)
+      tag_names = Tag.where(name: tag_names).pluck(:name)
     end
 
-    return tags[0...SiteSetting.max_tags_per_topic]
+    return tag_names[0...SiteSetting.max_tags_per_topic]
   end
 
   def self.notification_key(tag_id)

spec/integration/category_tag_spec.rb

@@ -0,0 +1,55 @@
+# encoding: UTF-8
+
+require 'rails_helper'
+require_dependency 'post_creator'
+
+describe "category tag restrictions" do
+  let!(:tag1) { Fabricate(:tag) }
+  let!(:tag2) { Fabricate(:tag) }
+  let!(:tag3) { Fabricate(:tag) }
+  let!(:tag4) { Fabricate(:tag) }
+
+  let(:user)  { Fabricate(:user) }
+  let(:admin) { Fabricate(:admin) }
+
+  before do
+    SiteSetting.tagging_enabled = true
+    SiteSetting.min_trust_to_create_tag = 0
+    SiteSetting.min_trust_level_to_tag_topics = 0
+  end
+
+  context "tags restricted to one category" do
+    let(:category_with_tags) { Fabricate(:category) }
+    let(:other_category)     { Fabricate(:category) }
+
+    before do
+      category_with_tags.tags = [tag1, tag2]
+    end
+
+    it "tags belonging to that category can only be used there" do
+      post = create_post(category: category_with_tags, tags: [tag1.name, tag2.name, tag3.name])
+      expect(post.topic.tags.map(&:name).sort).to eq([tag1.name, tag2.name].sort)
+
+      post = create_post(category: other_category, tags: [tag1.name, tag2.name, tag3.name])
+      expect(post.topic.tags.map(&:name)).to eq([tag3.name])
+    end
+
+    it "search can show only permitted tags" do
+      expect(DiscourseTagging.filter_allowed_tags(Tag.all, Guardian.new(user)).count).to eq(Tag.count)
+      expect(DiscourseTagging.filter_allowed_tags(Tag.all, Guardian.new(user), {for_input: true, category: category_with_tags}).pluck(:name).sort).to eq([tag1.name, tag2.name].sort)
+      expect(DiscourseTagging.filter_allowed_tags(Tag.all, Guardian.new(user), {for_input: true}).pluck(:name).sort).to eq([tag3.name, tag4.name].sort)
+    end
+
+    it "can't create new tags in a restricted category" do
+      post = create_post(category: category_with_tags, tags: [tag1.name, "newtag"])
+      expect(post.topic.tags.map(&:name)).to eq([tag1.name])
+      post = create_post(category: category_with_tags, tags: [tag1.name, "newtag"], user: admin)
+      expect(post.topic.tags.map(&:name)).to eq([tag1.name])
+    end
+
+    it "can create new tags in a non-restricted category" do
+      post = create_post(category: other_category, tags: [tag3.name, "newtag"])
+      expect(post.topic.tags.map(&:name).sort).to eq([tag3.name, "newtag"].sort)
+    end
+  end
+end