#399

backend/app/services/post_create_plan.rb

@@ -87,7 +87,7 @@ class PostCreatePlan
     end
     raise Tag::SectionLiteralParseError.new(raw_name, raw_name) if name.include?('[') || name.include?(']')
 
-    [TagName.canonicalise(name).first, category&.to_sym, sections]
+    [resolved_tag_name(name), category&.to_sym, sections]
   end
 
   def build_default_tag_specs direct_tag_specs
@@ -254,4 +254,11 @@ class PostCreatePlan
       end
     end
   end
+
+  def resolved_tag_name name
+    tag_name = TagName.includes(:canonical).find_by(name:)
+    return name if tag_name.nil?
+
+    (tag_name.canonical || tag_name).name
+  end
 end

backend/app/services/post_import_previewer.rb

@@ -3,14 +3,14 @@ require 'timeout'
 
 class PostImportPreviewer
   FIELDS = [
-    'title',
-    'thumbnail_base',
-    'original_created_from',
-    'original_created_before',
-    'video_ms',
-    'duration',
-    'tags',
-    'parent_post_ids'].freeze
+      'title',
+      'thumbnail_base',
+      'original_created_from',
+      'original_created_before',
+      'video_ms',
+      'duration',
+      'tags',
+      'parent_post_ids'].freeze
   FETCH_WARNING_FIELDS = ['url', 'title', 'thumbnail_base'].freeze
   TITLE_FETCH_WARNING = 'タイトルを取得できませんでした．'.freeze
   THUMBNAIL_FETCH_WARNING = 'サムネールを取得できませんでした．'.freeze
@@ -126,7 +126,6 @@ class PostImportPreviewer
     validate_basic_data(attributes, validation_errors)
     validate_preview_tags(merged_tags(tag_sources, provenance['tags']),
                           validation_errors,
-                          field_warnings,
                           known_tags)
     validate_parents(attributes['parent_post_ids'], validation_errors, existing_parent_ids)
     attributes.delete('url')
@@ -450,7 +449,7 @@ class PostImportPreviewer
     []
   end
 
-  def validate_preview_tags raw, errors, field_warnings, known_tags
+  def validate_preview_tags raw, errors, known_tags
     names = raw.to_s.split
     return if names.empty?
     if names.any? { _1.downcase.start_with?('nico:') }
@@ -462,11 +461,6 @@ class PostImportPreviewer
     existing = parsed.filter_map { known_tags[_1] }
     deprecated = existing.select(&:deprecated?).map(&:name)
     errors[:tags] = ["廃止済みタグがあります: #{ deprecated.join(' ') }"] if deprecated.present?
-    known = existing.reject(&:deprecated?).map(&:name)
-    new_tags = parsed.uniq - known
-    if new_tags.present?
-      add_field_warning!(field_warnings, 'tags', "新規タグを作成します: #{ new_tags.join(' ') }")
-    end
   rescue Tag::SectionLiteralParseError
     errors[:tags] = ['タグ区間の記法が不正です．']
   end