AI: address review on PR #469

backend/app/models/post_implication.rb

@@ -8,6 +8,7 @@ class PostImplication < ApplicationRecord
   validates :parent_post_id, presence: true
 
   validate :parent_post_mustnt_be_itself
+  validate :parent_post_mustnt_create_cycle
 
   private
 
@@ -16,4 +17,24 @@ class PostImplication < ApplicationRecord
       errors.add :parent_post_id, '親投稿に同じ投稿を設定することはできません．'
     end
   end
+
+  def parent_post_mustnt_create_cycle
+    return if post_id.blank? || parent_post_id.blank?
+    return if errors[:parent_post_id].present?
+
+    ancestor_ids = Set.new
+    frontier_ids = [parent_post_id]
+
+    until frontier_ids.empty?
+      if frontier_ids.include?(post_id)
+        errors.add :parent_post_id, :invalid
+        return
+      end
+
+      ancestor_ids.merge(frontier_ids)
+      frontier_ids = PostImplication.where(post_id: frontier_ids)
+          .distinct.pluck(:parent_post_id)
+          .reject { ancestor_ids.include?(_1) }
+    end
+  end
 end

backend/app/services/post_tag_search.rb

@@ -3,8 +3,8 @@ class PostTagSearch
   def self.literals(locale, raw)
     tokens = raw.split.reject { _1.downcase == 'type:or' }
     names = tokens.map { _1.sub(/\Anot:/i, '') }
-    registered = matching_names(TagName.where(language_code: locale.language_code),
-        names, 'tag_names.name', :tag_id).to_h
+    registered = TagName.where(language_code: locale.language_code, name: names)
+        .pluck(:name, :tag_id).to_h
     primary = TagName.where(language_code: locale.language_code,
         tag_id: registered.values, primary_flg: true).pluck(:tag_id, :name).to_h
     tokens.zip(names).map do |token, name|
@@ -19,25 +19,12 @@ class PostTagSearch
 
   def self.references_for(locale, literals)
     names = literals.map { _1[:name] }.uniq
-    internal = matching_names(TagName.where(language_code: locale.language_code),
-        names, 'tag_names.name', :tag_id).group_by(&:first)
-    external = matching_names(ExternalTag.all, names,
-        "CONCAT(external_tags.platform, ':', external_tags.name)", :id).group_by(&:first)
+    internal = TagName.where(language_code: locale.language_code, name: names)
+        .pluck(:name, :tag_id).group_by(&:first)
+    external = names.empty? ? {} : ExternalTag.where(
+        "CONCAT(platform, ':', name) IN (?)", names)
+        .pluck(Arel.sql("CONCAT(platform, ':', name)"), :id).group_by(&:first)
     names.to_h { |name| [name, [internal.fetch(name, []).map(&:last).uniq,
                               external.fetch(name, []).map(&:last).uniq]] }
   end
-
-  def self.matching_names(scope, names, expression, identifier)
-    return [] if names.empty?
-
-    queries = names.uniq.map do |name|
-      scope.klass.sanitize_sql_array(['SELECT ? AS name', name])
-    end
-    # Return the input spelling so Ruby does not recheck database equivalence.
-    scope.joins(<<~SQL).pluck(Arel.sql('search_names.name'), identifier)
-      INNER JOIN (#{ queries.join(' UNION ALL ') }) AS search_names
-        ON #{ expression } = search_names.name COLLATE utf8mb4_0900_ai_ci
-    SQL
-  end
-  private_class_method :matching_names
 end

backend/spec/models/post_implication_spec.rb

@@ -48,4 +48,47 @@ RSpec.describe PostImplication, type: :model do
     expect(duplicate).not_to be_valid
     expect(duplicate.errors[:post_id]).to be_present
   end
+
+  it 'rejects a parent that would create a two-post cycle' do
+    described_class.create!(post: post_record, parent_post:)
+
+    implication = described_class.new(
+        post: parent_post, parent_post: post_record)
+
+    expect(implication).not_to be_valid
+    expect(implication.errors.of_kind?(:parent_post_id, :invalid)).to be true
+  end
+
+  it 'rejects a parent that would create a three-post cycle' do
+    ancestor_post = create(:post)
+    described_class.create!(post: post_record, parent_post:)
+    described_class.create!(post: parent_post, parent_post: ancestor_post)
+
+    implication = described_class.new(
+        post: ancestor_post, parent_post: post_record)
+
+    expect(implication).not_to be_valid
+    expect(implication.errors.of_kind?(:parent_post_id, :invalid)).to be true
+  end
+
+  it 'allows a parent with an ancestor when no cycle would result' do
+    ancestor_post = create(:post)
+    described_class.create!(post: parent_post, parent_post: ancestor_post)
+
+    implication = described_class.new(post: post_record, parent_post:)
+
+    expect(implication).to be_valid
+  end
+
+  it 'terminates when existing ancestors already contain a cycle' do
+    ancestor_post = create(:post)
+    described_class.create!(post: parent_post, parent_post: ancestor_post)
+    legacy_implication = described_class.new(
+        post: ancestor_post, parent_post:)
+    legacy_implication.save!(validate: false)
+
+    implication = described_class.new(post: post_record, parent_post:)
+
+    expect(implication).to be_valid
+  end
 end

backend/spec/requests/posts_spec.rb

@@ -206,25 +206,6 @@ RSpec.describe 'Posts API', type: :request do
     end
 
     context 'when q is provided' do
-      ['SPEC_TAG', 'SpEc_TaG', 'spec_tág', 'MANKO', 'MaNkO', 'mánko'].each do |name|
-        it "matches #{ name } using database collation" do
-          get '/posts', params: { locale: 'ja', tags: name }
-
-          expect(response).to have_http_status(:ok)
-          expect(json.fetch('count')).to eq(2)
-          expect(json.fetch('posts').map { _1.fetch('id') })
-              .to contain_exactly(post_record.id, hit_post.id)
-        end
-
-        it "excludes #{ name } using database collation" do
-          get '/posts', params: { locale: 'ja', tags: "not:#{ name }" }
-
-          expect(response).to have_http_status(:ok)
-          expect(json.fetch('count')).to eq(1)
-          expect(json.fetch('posts').map { _1.fetch('id') }).to eq([miss_post.id])
-        end
-      end
-
       it 'filters posts by q (hit case)' do
         get '/posts', params: { tags: 'spec_tag' }
 
@@ -285,26 +266,6 @@ RSpec.describe 'Posts API', type: :request do
         PostExternalTag.create!(post: miss_post, external_tag:)
       end
 
-      ['NICO:SEARCH_EXTERNAL', 'NiCo:SeArCh_ExTeRnAl', 'nico:séarch_external'].each do |name|
-        it "matches #{ name } using database collation" do
-          get '/posts', params: { locale: 'ja', tags: name }
-
-          expect(response).to have_http_status(:ok)
-          expect(json.fetch('count')).to eq(2)
-          expect(json.fetch('posts').map { _1.fetch('id') })
-              .to contain_exactly(miss_post.id, both_post.id)
-        end
-
-        it "excludes #{ name } using database collation" do
-          get '/posts', params: { locale: 'ja', tags: "not:#{ name }" }
-
-          expect(response).to have_http_status(:ok)
-          expect(json.fetch('count')).to eq(2)
-          expect(json.fetch('posts').map { _1.fetch('id') })
-              .to contain_exactly(post_record.id, hit_post.id)
-        end
-      end
-
       it 'keeps internal name searches independent of colliding external ids' do
         get '/posts', params: { tags: primary_tag_name_for(tag, 'ja').name }