backend/app/controllers/posts_controller.rb

@@ -148,10 +148,10 @@ class PostsController < ApplicationController
     ApplicationRecord.transaction do
       post.save!
 
-      tags = Tag.normalise_tags!(tag_names)
+      tags = Tag.normalise_tags!(tag_names, deny_deprecated: true)
       TagVersioning.record_tag_snapshots!(tags, created_by_user: current_user)
 
-      tags = Tag.expand_parent_tags(tags)
+      tags = Tag.expand_parent_tags(tags).reject(&:deprecated?)
       sync_post_tags!(post, tags)
 
       sync_parent_posts!(post, parent_post_ids)
@@ -165,6 +165,8 @@ class PostsController < ApplicationController
     render json: PostRepr.base(post), status: :created
   rescue Tag::NicoTagNormalisationError
     render_validation_error fields: { tags: 'ニコニコ・タグは直接指定できません．' }
+  rescue Tag::DeprecatedTagNormalisationError
+    render_unprocessable_entity '廃止済みタグは付与できません．', field: :tags
   rescue ArgumentError => e
     render_validation_error fields: { parent_post_ids: [e.message] }
   rescue ActiveRecord::RecordInvalid => e
@@ -255,6 +257,8 @@ class PostsController < ApplicationController
     render json:, status: :ok
   rescue Tag::NicoTagNormalisationError
     render_validation_error fields: { tags: ['ニコニコ・タグは直接指定できません．'] }
+  rescue Tag::DeprecatedTagNormalisationError
+    render_unprocessable_entity '廃止済みタグは付与できません．', field: :tags
   rescue ArgumentError => e
     render_validation_error fields: { parent_post_ids: [e.message] }
   rescue ActiveRecord::RecordInvalid => e
@@ -378,7 +382,7 @@ class PostsController < ApplicationController
   end
 
   def build_tag_tree_for tags
-    tags = tags.to_a
+    tags = tags.reject(&:deprecated?).to_a
     tag_ids = tags.map(&:id)
 
     implications = TagImplication.where(parent_tag_id: tag_ids, tag_id: tag_ids)
@@ -501,7 +505,8 @@ class PostsController < ApplicationController
   end
 
   def editable_tag_names_from_post post
-    post.tags.not_nico.joins(:tag_name).order('tag_names.name').pluck('tag_names.name')
+    post.tags.not_nico.where(deprecated_at: nil)
+        .joins(:tag_name).order('tag_names.name').pluck('tag_names.name')
   end
 
   def post_incoming_snapshot title:, original_created_from:, original_created_before:,
@@ -533,9 +538,10 @@ class PostsController < ApplicationController
   end
 
   def incoming_tag_names_for_snapshot raw_tag_names
-    tags = Tag.normalise_tags!(raw_tag_names, with_tagme: false)
+    tags = Tag.normalise_tags!(raw_tag_names, with_tagme: false,
+                                              deny_deprecated: true)
 
-    Tag.expand_parent_tags(tags).map(&:name).uniq.sort
+    Tag.expand_parent_tags(tags).reject(&:deprecated?).map(&:name).uniq.sort
   end
 
   def post_conflict_json post:, base_version_no:, base_snapshot:,
@@ -622,13 +628,14 @@ class PostsController < ApplicationController
                  original_created_from: snapshot[:original_created_from],
                  original_created_before: snapshot[:original_created_before])
 
-    editable_tags = Tag.normalise_tags!(snapshot[:tag_names], with_tagme: false)
+    editable_tags = Tag.normalise_tags!(snapshot[:tag_names], with_tagme: false,
+                                                               deny_deprecated: true)
     TagVersioning.record_tag_snapshots!(editable_tags, created_by_user: current_user)
 
     readonly_tags = post.tags.nico.to_a
 
     tags = readonly_tags + editable_tags
-    tags = Tag.expand_parent_tags(tags)
+    tags = Tag.expand_parent_tags(tags).reject(&:deprecated?)
 
     sync_post_tags!(post, tags)
     sync_parent_posts!(post, snapshot[:parent_post_ids])

backend/app/models/tag.rb

@@ -8,6 +8,15 @@ class Tag < ApplicationRecord
     ;
   end
 
+  class DeprecatedTagNormalisationError < ArgumentError
+    attr_reader :tag_names
+
+    def initialize tag_names
+      @tag_names = Array(tag_names)
+      super('deprecated tags are not allowed')
+    end
+  end
+
   has_many :post_tags, inverse_of: :tag
   has_many :active_post_tags, -> { kept }, class_name: 'PostTag', inverse_of: :tag
   has_many :post_tags_with_discarded, -> { with_discarded }, class_name: 'PostTag'
@@ -95,7 +104,8 @@ class Tag < ApplicationRecord
 
   def self.normalise_tags! tag_names, with_tagme: true,
                                       with_no_deerjikist: true,
-                                      deny_nico: true
+                                      deny_nico: true,
+                                      deny_deprecated: false
     if deny_nico && tag_names.any? { |n| n.downcase.start_with?('nico:') }
       raise NicoTagNormalisationError
     end
@@ -104,6 +114,10 @@ class Tag < ApplicationRecord
       pf, cat = CATEGORY_PREFIXES.find { |p, _| name.downcase.start_with?(p) } || ['', nil]
       name = TagName.canonicalise(name.sub(/\A#{ pf }/i, '')).first
       find_or_create_by_tag_name!(name, category: (cat || :general)).tap do |tag|
+        if deny_deprecated && tag.deprecated?
+          raise DeprecatedTagNormalisationError, [tag.name]
+        end
+
         tag.update!(category: cat) if cat && tag.category != cat
       end
     end

backend/app/representations/post_repr.rb

@@ -53,7 +53,7 @@ module PostRepr
   end
 
   def tag_json tags
-    tags.map { |tag| TagRepr.inline(tag) }
+    tags.reject(&:deprecated?).map { |tag| TagRepr.inline(tag) }
   end
 
   def thumbnail_url post