FIX: tag info misleading message saying it's not restricted

When a tag is restricted to a secured category that the user can't see,
the message was saying that it wasn't restricted to any categories.
Now it will say it's restricted to categories you can't access.

app/assets/javascripts/discourse/templates/components/tag-info.hbs

@@ -22,7 +22,11 @@
         {{/each}}
       {{/if}}
       {{#if nothingToShow}}
-        {{i18n "tagging.default_info"}}
+        {{#if tagInfo.category_restricted}}
+          {{i18n "tagging.category_restricted"}}
+        {{else}}
+          {{i18n "tagging.default_info"}}
+        {{/if}}
       {{/if}}
     </div>
     {{#if tagInfo.synonyms}}

app/serializers/detailed_tag_serializer.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 class DetailedTagSerializer < TagSerializer
-  attributes :synonyms, :tag_group_names
+  attributes :synonyms, :tag_group_names, :category_restricted
 
   has_many :categories, serializer: BasicCategorySerializer
 
@@ -10,12 +10,11 @@ class DetailedTagSerializer < TagSerializer
   end
 
   def categories
-    Category.secured(scope).where(
-      id: object.categories.pluck(:id) +
-        object.tag_groups.includes(:categories).map do |tg|
-          tg.categories.map(&:id)
-        end.flatten
-    )
+    Category.secured(scope).where(id: category_ids)
+  end
+
+  def category_restricted
+    !category_ids.empty?
   end
 
   def include_tag_group_names?
@@ -25,4 +24,13 @@ class DetailedTagSerializer < TagSerializer
   def tag_group_names
     object.tag_groups.map(&:name)
   end
+
+  private
+
+  def category_ids
+    @_category_ids ||= object.categories.pluck(:id) +
+      object.tag_groups.includes(:categories).map do |tg|
+        tg.categories.map(&:id)
+      end.flatten
+  end
 end

config/locales/client.en.yml

@@ -3100,6 +3100,7 @@ en:
       choose_for_topic: "optional tags"
       info: "Info"
       default_info: "This tag isn't restricted to any categories, and has no synonyms."
+      category_restricted: "This tag is restricted to categories you don't have permission to access."
       synonyms: "Synonyms"
       synonyms_description: "When the following tags are used, they will be replaced with <b>%{base_tag_name}</b>."
       tag_groups_info:

spec/requests/tags_controller_spec.rb

@@ -191,6 +191,7 @@ describe TagsController do
       expect(json.dig('tag_info', 'name')).to eq(tag.name)
       expect(json.dig('tag_info', 'synonyms')).to be_empty
       expect(json.dig('tag_info', 'category_ids')).to be_empty
+      expect(json.dig('tag_info', 'category_restricted')).to eq(false)
     end
 
     it "can handle a synonym" do
@@ -199,6 +200,7 @@ describe TagsController do
       expect(json.dig('tag_info', 'name')).to eq(synonym.name)
       expect(json.dig('tag_info', 'synonyms')).to be_empty
       expect(json.dig('tag_info', 'category_ids')).to be_empty
+      expect(json.dig('tag_info', 'category_restricted')).to eq(false)
     end
 
     it "can return a tag's synonyms" do
@@ -230,6 +232,7 @@ describe TagsController do
       get "/tag/#{tag.name}/info.json"
       expect(json.dig('tag_info', 'category_ids')).to contain_exactly(category.id, category2.id)
       expect(json['categories']).to be_present
+      expect(json.dig('tag_info', 'category_restricted')).to eq(true)
     end
 
     context 'tag belongs to a tag group' do
@@ -246,6 +249,39 @@ describe TagsController do
         get "/tag/#{tag.name}/info.json"
         expect(json['tag_info'].has_key?('tag_group_names')).to eq(false)
       end
+
+      context "restricted to a private category" do
+        let!(:private_category) do
+          Fabricate(:private_category,
+            group: Fabricate(:group),
+            tag_groups: [tag_group],
+            allow_global_tags: true
+          )
+        end
+
+        it "can return categories to users who can access them" do
+          sign_in(admin)
+          get "/tag/#{tag.name}/info.json"
+          expect(json.dig('tag_info', 'category_ids')).to contain_exactly(private_category.id)
+          expect(json['categories']).to be_present
+          expect(json.dig('tag_info', 'category_restricted')).to eq(true)
+        end
+
+        it "can indicate category restriction to users who can't access them" do
+          sign_in(user)
+          get "/tag/#{tag.name}/info.json"
+          expect(json.dig('tag_info', 'category_ids')).to be_empty
+          expect(json['categories']).to be_blank
+          expect(json.dig('tag_info', 'category_restricted')).to eq(true)
+        end
+
+        it "can indicate category restriction to anon" do
+          get "/tag/#{tag.name}/info.json"
+          expect(json.dig('tag_info', 'category_ids')).to be_empty
+          expect(json['categories']).to be_blank
+          expect(json.dig('tag_info', 'category_restricted')).to eq(true)
+        end
+      end
     end
   end