#442

backend/app/models/history_access.rb

@@ -4,7 +4,7 @@ require 'digest'
 class HistoryAccess < ActiveSupport::CurrentAttributes
   attribute :user
   class Forbidden < StandardError; end
-  ARTIFACT_POLICY = 'counts-private-predicates-4'.freeze
+  ARTIFACT_POLICY = 'counts-masked-summary-1'.freeze
 
   KEYS = { 'post_versions' => ['post_id'], 'tag_versions' => ['tag_id'],
            'nico_tag_versions' => ['tag_id'],

backend/app/services/counts_axes.rb

@@ -1,41 +1,12 @@
 class CountsAxes
   MAX_AXES = 8
-  MASKED_TEXT = '********'.freeze
   MASKED_VALUE = '__counts_private__'.freeze
-  PUBLIC_FIELDS = ['resource_id', 'version_no', 'event_type', 'user',
-                   'created_at'].freeze
+  PUBLIC_FIELDS = ['created_at', 'event_type'].freeze
   class TooManyAxes < ArgumentError; end
   class PrivateCondition < ArgumentError; end
 
   GRAINS = ['year', 'quarter', 'month', 'week', 'day', 'hour'].freeze
 
-  def self.private_field?(field)
-    !PUBLIC_FIELDS.include?(field) && field != 'user.id'
-  end
-
-  def self.visible_ids_sql(definition)
-    "SELECT counts_visible.id FROM #{ definition.table } counts_visible WHERE " +
-        HistoryAccess.sql(definition.model, 'counts_visible')
-  end
-
-  def self.visibility_sql(definition, field)
-    return 'TRUE' if HistoryAccess.admin?
-
-    source = visible_ids_sql(definition)
-    visible = "v.id IN (#{ source })"
-    return visible unless field == 'changed_field'
-
-    "(#{ visible }) AND (previous.id IS NULL OR previous.id IN (#{ source }))"
-  end
-
-  def self.masked_sql(expression, definition, field)
-    return expression if HistoryAccess.admin? || !private_field?(field)
-
-    visible = visibility_sql(definition, field)
-    quoted = ApplicationRecord.connection.quote(MASKED_VALUE)
-    "CASE WHEN #{ visible } THEN #{ expression } ELSE #{ quoted } END"
-  end
-
   def self.time_expression(expression, grain, timezone)
     raise ArgumentError unless GRAINS.include?(grain)
 
@@ -89,9 +60,13 @@ class CountsAxes
         @definition.fields[field] == :datetime ? self.class.time_expression(
             expression, axis.fetch('grain', 'month'), @population.timezone) : expression
       end
-      if !HistoryAccess.admin? && self.class.private_field?(field)
-        expression = self.class.masked_sql(
-            "CAST((#{ expression }) AS CHAR)", @definition, field)
+      if !HistoryAccess.admin? && !PUBLIC_FIELDS.include?(field)
+        visible = HistoryAccess.sql(@definition.model, 'v')
+        if field == 'changed_field'
+          visible = "(#{ visible }) AND (#{ HistoryAccess.sql(@definition.model, 'previous') })"
+        end
+        expression = "CASE WHEN #{ visible } " +
+            "THEN CAST((#{ expression }) AS CHAR) ELSE '#{ MASKED_VALUE }' END"
       end
       expression
     end
@@ -102,12 +77,10 @@ class CountsAxes
     selected = indexes.map { "#{ expressions[_1] } AS a#{ _1 }" }
     identities = ['v.id']
     if rows.any? { _1['field'] == 'tags' }
-      identities << self.class.masked_sql(
-          "COALESCE(CONCAT('internal:', tag_entry.tag_id), " +
-              "CONCAT('external:', tag_entry.external_tag_id))", @definition, 'tags')
-      if rows.any? { _1['field'] == 'changed_field' }
-        identities << self.class.masked_sql('changed.field_key', @definition, 'changed_field')
-      end
+      # Raw identities stay inside COUNT; masked tag occurrences remain additive.
+      identities << "COALESCE(CONCAT('internal:', tag_entry.tag_id), " +
+          "CONCAT('external:', tag_entry.external_tag_id))"
+      identities << 'changed.field_key' if rows.any? { _1['field'] == 'changed_field' }
     end
     members = identities.each_index.map { "counts_member_#{ _1 }" }
     selected += identities.each_with_index.map { |expression, index|
@@ -125,17 +98,8 @@ class CountsAxes
   def joins(fields = all.map { _1['field'] })
     result = ''
     if fields.include?('tags')
-      document = 'CAST(v.tags_json AS JSON)'
-      unless HistoryAccess.admin?
-        visible = self.class.visible_ids_sql(@definition)
-        result += " LEFT JOIN (#{ visible }) counts_tags_visible " +
-            'ON counts_tags_visible.id = v.id '
-        document = "CASE WHEN counts_tags_visible.id IS NOT NULL " +
-            "THEN #{ document } ELSE JSON_ARRAY(" +
-            "JSON_OBJECT('tag_id', 0)) END"
-      end
       result += <<~SQL.squish
-         JOIN JSON_TABLE(#{ document }, '$[*]' COLUMNS (
+         JOIN JSON_TABLE(CAST(v.tags_json AS JSON), '$[*]' COLUMNS (
           tag_id BIGINT PATH '$.tag_id' NULL ON EMPTY,
           external_tag_id BIGINT PATH '$.external_tag_id' NULL ON EMPTY)) tag_entry
 
@@ -148,13 +112,6 @@ class CountsAxes
       condition = @definition.changes.map do |field|
         "(changed.field_key = '#{ field }' AND #{ @population.changed_sql(field) })"
       end.join(' OR ')
-      unless HistoryAccess.admin?
-        visible = self.class.visibility_sql(@definition, 'changed_field')
-        marker = ApplicationRecord.connection.quote(MASKED_VALUE)
-        fields += " UNION ALL SELECT #{ marker } AS field_key"
-        condition = "((#{ visible }) AND (#{ condition })) OR " +
-            "(NOT (#{ visible }) AND changed.field_key = #{ marker })"
-      end
       result += " JOIN (#{ fields }) changed ON (#{ condition })"
     end
     result

backend/app/services/counts_condition.rb

@@ -82,32 +82,14 @@ class CountsCondition
 
   def apply(scope, entry)
     raise ArgumentError unless entry.is_a?(Hash)
-
     if entry['operator'] == 'axis_eq'
       raise ArgumentError unless (entry.keys - ['field', 'operator', 'grain', 'value']).empty?
       value = entry['value']
-      unless (value.nil? || value.is_a?(String) || value.is_a?(Numeric) ||
-          [true, false].include?(value))
+      unless value.nil? || value.is_a?(String) || value.is_a?(Numeric) || [true, false].include?(value)
         raise ArgumentError
       end
       raise ArgumentError if value.is_a?(String) && value.bytesize > 8192
 
-      if (!HistoryAccess.admin? && CountsAxes.private_field?(entry['field']) &&
-          (value == CountsAxes::MASKED_VALUE ||
-              (value == CountsAxes::MASKED_TEXT &&
-                  (@definition.fields[entry['field']] != :string ||
-                      ['tags', 'changed_field'].include?(entry['field'])))))
-        field = entry.fetch('field')
-        raise ArgumentError unless @definition.axes(@population.history).include?(field)
-        if entry.key?('grain')
-          unless (@definition.fields[field] == :datetime &&
-              CountsAxes::GRAINS.include?(entry['grain']))
-            raise ArgumentError
-          end
-        end
-        return scope.none
-      end
-      scope = @population.condition_scope(scope, entry.fetch('field'))
       return @population.axis_condition(scope, entry)
     end
     allowed = ['field', 'operator', 'value', 'end', 'blank', 'input', 'values']
@@ -129,13 +111,6 @@ class CountsCondition
 
     source, expression = source_for(field[:key])
     type = field[:type]
-    # Preserve typed input compatibility; display markers are never real typed values.
-    if (!HistoryAccess.admin? && CountsAxes.private_field?(field[:key]) &&
-        entry['value'] == CountsAxes::MASKED_TEXT && type != :string && !entry['blank'])
-      return scope.none unless entry['operator'] == 'ne'
-
-      return @population.condition_scope(scope, field[:key])
-    end
     blank = blank_sql(expression, type)
     if entry['blank']
       sql = if source && field[:collection]
@@ -144,7 +119,6 @@ class CountsCondition
               "NOT EXISTS (SELECT 1 FROM #{ source } WHERE NOT (#{ blank }))"
             else blank
             end
-      scope = @population.condition_scope(scope, field[:key])
       return scope.where(Arel.sql(sql))
     end
     if ['in', 'not_in', 'any', 'all', 'none'].include?(entry['operator'])
@@ -157,7 +131,6 @@ class CountsCondition
     validate_enum!(field[:key], parsed.first) if type == :enum
     operator = entry['operator']
     if type == :interval
-      scope = @population.condition_scope(scope, field[:key])
       return interval(scope, source, expression, parsed)
     end
     clauses = []
@@ -185,7 +158,6 @@ class CountsCondition
     elsif operator == 'ne'
       predicate = "(NOT (#{ predicate }) OR #{ blank })"
     end
-    scope = @population.condition_scope(scope, field[:key])
     scope.where(predicate, *binds)
   end
 
@@ -196,13 +168,6 @@ class CountsCondition
 
     values = entry['values']
     raise ArgumentError unless values.is_a?(Array) && values.length <= 100
-    if (!HistoryAccess.admin? && CountsAxes.private_field?(field[:key]) &&
-        values.include?(CountsAxes::MASKED_TEXT) &&
-        (field[:type] != :string || field[:set_type] == 'tag_reference'))
-      return scope.none if entry['operator'] == 'all'
-
-      values = values - [CountsAxes::MASKED_TEXT]
-    end
     raise ArgumentError if [entry['value'], entry['end']].any? { !_1.nil? && _1 != '' }
 
     parsed = values.map do |value|
@@ -226,10 +191,7 @@ class CountsCondition
 
     operator = entry['operator']
     if parsed.empty?
-      return scope.none if ['in', 'any'].include?(operator)
-      return scope if entry['values'].empty?
-
-      return @population.condition_scope(scope, field[:key])
+      return ['in', 'any'].include?(operator) ? scope.none : scope
     end
     source, expression = source_for(field[:key])
     if field[:set_type] == 'tag_reference'
@@ -250,7 +212,6 @@ class CountsCondition
       predicate = source ? "NOT #{ predicate }" :
           "(NOT #{ predicate } OR #{ blank_sql(expression, field[:type]) })"
     end
-    scope = @population.condition_scope(scope, field[:key])
     scope.where(predicate, *parsed)
   end
 

backend/app/services/counts_population.rb

@@ -70,13 +70,6 @@ class CountsPopulation
     @authorisation_flg ? HistoryAccess.sql(model, row) : 'TRUE'
   end
 
-  # Each predicate keeps its own visibility restriction, including OR branches.
-  def condition_scope(scope, field)
-    return scope if HistoryAccess.admin? || !CountsAxes.private_field?(field)
-
-    scope.where(Arel.sql(CountsAxes.visibility_sql(definition, field)))
-  end
-
   def axis_condition(scope, entry)
     raise CountsAxes::PrivateCondition if entry['value'] == CountsAxes::MASKED_VALUE
 
@@ -216,7 +209,6 @@ class CountsPopulation
   def apply_tags
     raise ArgumentError unless definition.resource == 'posts'
 
-    @scope = condition_scope(@scope, 'tags')
     if params['tag'].present?
       @scope = @scope.where(snapshot_membership(
           "#{ params.fetch('kind', 'internal') }:#{ params['tag'] }"))

backend/app/services/counts_table_export.rb

@@ -253,7 +253,7 @@ class CountsTableExport
   end
 
   def summary_value(value, index, page)
-    return CountsAxes::MASKED_TEXT if value == CountsAxes::MASKED_VALUE
+    return '********' if value == CountsAxes::MASKED_VALUE
 
     field = @query.axes.all.fetch(index).fetch('field')
     return @labels.fetch('bot', '') if field == 'user' && value.nil?

backend/app/services/counts_table_query.rb

@@ -220,11 +220,19 @@ class CountsTableQuery
 
   private
 
-  # Private predicates require visibility independently of their operator.
-  # Ordering/measure state must not select a server-only masked coordinate.
+  # Public timeline predicates may include hidden records. Private predicates must
+  # never become a count oracle, even when the selected axes themselves are public.
   def validate_summary_conditions!
     return if mode != 'summary' || HistoryAccess.admin?
 
+    fields = QueryState.records(@params, 'conditions') + QueryState.records(@params, 'drill')
+    private_fields = fields.any? { !CountsAxes::PUBLIC_FIELDS.include?(_1['field']) }
+    keys = ['tags', 'tag', 'kind', 'resource_id', 'user_id']
+    private_parameters = keys.any? do |key|
+      @params.any? { |name, value| (name == key || name.start_with?("#{ key }.")) && value != '' }
+    end
+    raise CountsAxes::PrivateCondition if private_fields || private_parameters
+
     ['column_order', 'measures'].each do |key|
       # Coordinates are compared only to already masked expressions, never raw
       # values. Public coordinates remain sortable; a guessed private ID cannot match.

backend/db/seeds.rb

@@ -9,21 +9,8 @@
 #   end
 
 ApplicationRecord.transaction do
-  Language.find_or_create_by!(code: 'ja') { _1.name = '日本語' }
-  Script.find_or_create_by!(code: 'Jpan') { _1.name = '漢字、仮名文字およびラテン文字' }
-  Region.find_or_create_by!(code: 392) do
-    _1.alpha_code = 'JP'
-    _1.name = '日本国'
-  end
-  Locale.find_or_create_by!(code: 'ja') do
-    _1.language_code = 'ja'
-    _1.script_code = 'Jpan'
-    _1.region_code = 392
-    _1.name = '日本語'
-  end
-
-  Language.find_or_create_by!(code: 'ain') { _1.name = 'ヤウンモシルン　アイヌ　イタㇰ' }
-  Script.find_or_create_by!(code: 'Kana') { _1.name = 'カナモジ　オヨビ　ラテンモジ' }
+  Language.find_or_create_by!(code: 'ain') { _1.name = 'ain' }
+  Script.find_or_create_by!(code: 'Kana') { _1.name = 'Kana' }
 end
 
 post_url_sanitisation_rules = [

backend/spec/requests/counts_masked_search_spec.rb

@@ -1,196 +0,0 @@
-require 'rails_helper'
-
-RSpec.describe 'Counts masked search', type: :request do
-  let!(:tag) { create(:tag, primary_name: '秘密のタグ') }
-  let(:actor) { create(:user, :member) }
-  let(:admin) { create(:user, :admin) }
-  let(:base) do
-    { 'resource' => 'tags', 'definition' => 'history', 'mode' => 'summary',
-      'locale' => 'ja', 'execution_at' => '2025-01-01T00:00:00Z',
-      'timezone' => 'UTC', 'rows' => '', 'cols' => '', 'sort' => '' }
-  end
-
-  before do
-    [1, 2].each do |number|
-      TagVersion.create!(tag:, version_no: number,
-          event_type: number == 1 ? 'create' : 'discard', name: '秘密のタグ',
-          category: 'general', aliases: '秘密の別名', parent_tag_ids: '',
-          names: { ja: { name: '秘密のタグ', script_code: 'Jpan', auto_generated: false,
-                        aliases: [{ name: '秘密の別名', script_code: 'Jpan' }] } },
-          created_by_user: actor, created_at: Time.utc(2023, number))
-    end
-  end
-
-  def query(extra = {})
-    get '/counts/query', params: base.merge(extra)
-    expect(response).to have_http_status(:ok), extra.inspect
-    response.parsed_body
-  end
-
-  def predicate(field, operator, value, index = 0)
-    prefix = "conditions.#{ index }"
-    result = { 'conditions' => '', "#{ prefix }.field" => field,
-               "#{ prefix }.operator" => operator }
-    if ['in', 'any', 'all', 'none', 'not_in'].include?(operator)
-      result.merge!("#{ prefix }.values" => '1', 'condition_values' => '',
-          "condition_values.#{ index }.condition" => index.to_s,
-          "condition_values.#{ index }.value_type" => 'string',
-          "condition_values.#{ index }.value" => value)
-    else
-      result["#{ prefix }.value"] = value
-    end
-    result
-  end
-
-  it 'rejects every name and alias predicate on private history' do
-    ['name', 'name_ja', 'names.name', 'aliases.name', 'names.aliases.name'].each do |field|
-      secret = field.include?('aliases') ? '秘密の別名' : '秘密のタグ'
-      multiple = !['name', 'name_ja'].include?(field)
-      operators = multiple ? ['any', 'all', 'none'] : ['in', 'not_in']
-      ['eq', 'ne', 'like', *operators].each do |operator|
-        [secret, '********', '%', ''].each do |value|
-          expected = (value == '' && ['eq', 'ne', 'like'].include?(operator)) ? 2 : 0
-          expect(query(predicate(field, operator, value))['count']).to eq(expected)
-        end
-      end
-      blank = predicate(field, 'eq', '').merge('conditions.0.blank' => '1')
-      expect(query(blank)['count']).to eq(0)
-    end
-  end
-
-  it 'ignores missing and empty scalar values unless blank is checked' do
-    ['name', 'name_ja', 'names.name', 'aliases.name'].each do |field|
-      ['eq', 'ne', 'like'].each do |operator|
-        condition = predicate(field, operator, '')
-        [condition, condition.except('conditions.0.value')].each do |empty|
-          expect(query(empty)['count']).to eq(2)
-          expect(query(empty.merge('conditions.0.blank' => '0'))['count']).to eq(2)
-          expect(query(empty.merge('conditions.0.blank' => '1'))['count']).to eq(0)
-        end
-      end
-    end
-  end
-
-  it 'keeps details totals unchanged for inactive private predicates' do
-    settings = predicate('name', 'ne', '').merge('mode' => 'details')
-    result = query(settings)
-    expect(result['count']).to eq(0)
-    expect(result['versions']).to be_empty
-    expect(result['output_count']).to eq(2)
-    active = query(settings.merge('conditions.0.blank' => '1'))
-    expect(active['output_count']).to eq(0)
-  end
-
-  it 'ignores missing sets but preserves explicit empty set semantics' do
-    { 'name' => ['in', 'not_in'], 'aliases.name' => ['any', 'all', 'none'] }.each do
-        |field, operators|
-      operators.each do |operator|
-        condition = { 'conditions' => '', 'conditions.0.field' => field,
-                      'conditions.0.operator' => operator }
-        expect(query(condition)['count']).to eq(2)
-        empty = condition.merge('conditions.0.values' => '1', 'condition_values' => '')
-        expected = ['in', 'any'].include?(operator) ? 0 : 2
-        expect(query(empty)['count']).to eq(expected)
-        expect(query(condition.merge('conditions.0.blank' => '1'))['count']).to eq(0)
-        # An explicit empty string element is a real value, not an unspecified set.
-        expect(query(predicate(field, operator, ''))['count']).to eq(0)
-      end
-    end
-  end
-
-  it 'ignores empty private predicates regardless of their position' do
-    first = predicate('name', 'ne', '')
-        .merge(predicate('resource_id', 'eq', tag.id.to_s, 1))
-    last = predicate('resource_id', 'eq', tag.id.to_s)
-        .merge(predicate('aliases.name', 'like', '', 1))
-    expect(query(first)['count']).to eq(2)
-    expect(query(last)['count']).to eq(2)
-    active = predicate('name', 'ne', 'unrelated')
-        .merge(predicate('aliases.name', 'like', '', 1))
-    expect(query(active)['count']).to eq(0)
-  end
-
-  it 'searches public literal markers and treats axis predicates as explicit' do
-    public_tag = create(:tag, primary_name: '********')
-    TagVersion.create!(tag: public_tag, version_no: 1, event_type: 'create',
-        name: '********', category: 'general', aliases: '', parent_tag_ids: '',
-        names: { ja: { name: '********', script_code: 'Jpan', auto_generated: false,
-                      aliases: [] } }, created_at: Time.utc(2023))
-    expect(query['count']).to eq(3)
-    ['eq', 'ne', 'like', 'in', 'not_in'].each do |operator|
-      expected = ['ne', 'not_in'].include?(operator) ? 0 : 1
-      expect(query(predicate('name', operator, '********'))['count']).to eq(expected)
-    end
-    blank = predicate('aliases.name', 'eq', '').merge('conditions.0.blank' => '1')
-    expect(query(blank)['count']).to eq(1)
-    ['********', '', nil].each do |value|
-      condition = { 'conditions' => '', 'conditions.0.field' => 'name',
-                    'conditions.0.operator' => 'axis_eq',
-                    'conditions.0.value_type' => value.nil? ? 'null' : 'string' }
-      condition['conditions.0.value'] = value unless value.nil?
-      expected = value == '********' ? 1 : 0
-      expect(query(condition)['count']).to eq(expected)
-      drill = { 'drill' => '', 'drill.0.field' => 'name',
-                'drill.0.value_type' => value.nil? ? 'null' : 'string' }
-      drill['drill.0.value'] = value unless value.nil?
-      expect(query(drill)['count']).to eq(expected)
-    end
-  end
-
-  it 'keeps public identity and timeline predicates searchable' do
-    expect(query['count']).to eq(2)
-    values = { 'resource_id' => tag.id.to_s, 'version_no' => '2',
-               'event_type' => 'discard', 'user' => actor.id.to_s,
-               'created_at' => '2023-02-01T00:00:00Z' }
-    values.each do |field, value|
-      expected = ['resource_id', 'user'].include?(field) ? 2 : 1
-      expect(query(predicate(field, 'eq', value))['count']).to eq(expected)
-    end
-    condition = predicate('name', 'ne', '秘密のタグ')
-        .merge(predicate('event_type', 'eq', 'discard', 1))
-    expect(query(condition)['count']).to eq(0)
-    expect(query(predicate('category', 'eq', '********'))['count']).to eq(0)
-    expect(query(predicate('category', 'eq', 'general'))['count']).to eq(0)
-  end
-
-  it 'keeps public predicates available after combining multiple conditions' do
-    condition = predicate('resource_id', 'eq', tag.id.to_s)
-        .merge(predicate('event_type', 'eq', 'discard', 1))
-    expect(query(condition)['count']).to eq(1)
-    condition.merge!(predicate('name', 'ne', 'unrelated', 2))
-    expect(query(condition)['count']).to eq(0)
-  end
-
-  it 'keeps real name searches for administrators and excludes private details' do
-    condition = predicate('name', 'eq', '秘密のタグ')
-    details = query(condition.merge('mode' => 'details'))
-    expect(details['versions']).to be_empty
-    expect(details['output_count']).to eq(0)
-    masked = query(predicate('name', 'eq', '********').merge('mode' => 'details'))
-    expect(masked['versions']).to be_empty
-    expect(masked['output_count']).to eq(0)
-    sign_in_as(admin)
-    expect(query(condition)['count']).to eq(2)
-    expect(query(condition.merge('mode' => 'details'))['versions'].length).to eq(2)
-  end
-
-  it 'rejects private names reached through a post tag snapshot' do
-    post = create(:post)
-    PostVersion.create!(post:, version_no: 1, event_type: 'create', title: 'post',
-        url: post.url, tags: '', parent_post_ids: '',
-        tags_json: [{ tag_id: tag.id, version_no: 1, name: '秘密のタグ',
-                     category: 'general', sections: [] }],
-        created_at: Time.utc(2024))
-    ['tags.name', 'tags.names.name', 'tags.name_ja'].each do |field|
-      ['eq', 'ne', 'like', 'any', 'all', 'none'].each do |operator|
-        ['秘密のタグ', '********', '%'].each do |value|
-          settings = predicate(field, operator, value).merge('resource' => 'posts')
-          expect(query(settings)['count']).to eq(0)
-        end
-      end
-      blank = predicate(field, 'eq', '').merge('resource' => 'posts',
-          'conditions.0.blank' => '1')
-      expect(query(blank)['count']).to eq(0)
-    end
-  end
-end

backend/spec/requests/counts_table_spec.rb

@@ -354,25 +354,15 @@ RSpec.describe 'Counts table API', type: :request do
     expect(result['cells'].sum { _1['count'] }).to eq(4)
     expect(response.body).not_to include('hidden title')
     masked = query(mode: 'summary', rows: 'resource_id', cols: '')
-    expect(masked['cells'].map { _1['values'] }).to eq([[record.id]])
+    expect(masked['cells'].map { _1['values'] }).to eq([[CountsAxes::MASKED_VALUE]])
     expect(masked['cells'].first['count']).to eq(4)
     expect(query['versions']).to be_empty
   end
 
-  it 'allows public identity predicates without exposing private snapshot fields' do
-    PostVersion.create!(post: record, version_no: 4, event_type: 'discard',
-        url: record.url, title: 'hidden title', tags: '', tags_json: [],
-        parent_post_ids: '', created_at: Time.utc(2024, 3))
-
-    get '/counts/query', params: base.merge(mode: 'summary',
-        resource_id: record.id.to_s, rows: 'resource_id', cols: 'title')
-
-    expect(response).to have_http_status(:ok)
-    expect(json['count']).to eq(4)
-    expect(json['cells'].sum { _1['count'] }).to eq(4)
-    expect(json['cells'].map { _1['values'].last })
-        .to include(CountsAxes::MASKED_VALUE)
-    expect(response.body).not_to include('hidden title')
+  it 'rejects private summary predicates instead of exposing a count oracle' do
+    get '/counts/query', params: base.merge(mode: 'summary', resource_id: record.id.to_s)
+    expect(response).to have_http_status(:forbidden)
+    expect(json).to eq('error' => 'private_condition')
   end
 
   it 'reports the combined axis limit without replacing it with a generic 400' do

backend/spec/services/counts_pivot_security_spec.rb

@@ -69,29 +69,27 @@ RSpec.describe 'Counts masked pivot contracts' do
     end
   end
 
-  it 'counts one opaque collection per private version across pages' do
+  it 'preserves five tag occurrences after merging private tags and across pages' do
     [nil, guest, member, admin].each do |user|
       page = result(user)
-      expected = user == admin ? 5 : 6
-      expect(grand(page)).to eq(expected)
-      expect(page[:cells].sum { _1[:count] }).to eq(expected)
+      expect(grand(page)).to eq(5)
+      expect(page[:cells].sum { _1[:count] }).to eq(5)
       expect(page).not_to have_key(:excluded_count)
       paged = result(user, 'limit' => '1')
-      expect(grand(paged)).to eq(expected)
+      expect(grand(paged)).to eq(5)
       expect(result(user, 'limit' => '1', 'page' => '2')[:group_count])
           .to eq(page[:group_count])
     end
     public_page = result(nil)
     hidden = public_page[:cells].select { _1[:values].first == CountsAxes::MASKED_VALUE }
-    expect(hidden.sum { _1[:count] }).to eq(4)
+    expect(hidden.sum { _1[:count] }).to eq(3)
     expect(public_page[:axis_labels]['a0']).not_to have_key("internal:#{ tags.first.id }")
     expect(public_page.to_json).not_to include('hidden-title', 'private-discard')
   end
 
   it 'retains distinct membership when tags are not a row axis' do
     [nil, admin].each do |user|
-      expect(grand(result(user, 'rows' => 'event_type', 'cols' => 'tags')))
-          .to eq(user == admin ? 3 : 5)
+      expect(grand(result(user, 'rows' => 'event_type', 'cols' => 'tags'))).to eq(3)
       expect(result(user, 'rows' => '', 'cols' => '')[:cells].sole[:count]).to eq(5)
       details = result(user, 'mode' => 'details', 'rows' => '', 'cols' => '')
       expect(details[:count]).to eq(user == admin ? 5 : 1)
@@ -123,13 +121,14 @@ RSpec.describe 'Counts masked pivot contracts' do
   it 'counts distinct changed records when tags are not additive row tuples' do
     [nil, admin].each do |user|
       page = result(user, 'rows' => 'changed_field', 'cols' => 'event_type')
-      expect(grand(page)).to eq(user == admin ? 2 : 4)
+      expect(grand(page)).to eq(2)
       if user.nil?
         expect(page[:cells].map { _1[:values].first }.uniq).to eq([CountsAxes::MASKED_VALUE])
       end
-      # Private empty collections contribute the same opaque tuple as populated ones.
-      combined = result(user, 'rows' => 'changed_field', 'cols' => 'tags')
-      expect(grand(combined)).to eq(user == admin ? 0 : 4)
+      # Changed discard snapshots have no tags: no full cell contributes here.
+      empty = result(user, 'rows' => 'changed_field', 'cols' => 'tags')
+      expect(empty[:cells]).to be_empty
+      expect(grand(empty)).to eq(0)
     end
   end
 
@@ -143,7 +142,7 @@ RSpec.describe 'Counts masked pivot contracts' do
     expect(page[:row_headers]).to include(hash_including(values: [nil], kind: 'data'))
   end
 
-  it 'sorts public version numbers numerically including formerly hidden records' do
+  it 'sorts public numeric values numerically alongside a masked group' do
     post = PostVersion.order(:id).last.post
     [2, 10].each do |number|
       PostVersion.create!(post:, version_no: number, event_type: 'update',
@@ -152,196 +151,27 @@ RSpec.describe 'Counts masked pivot contracts' do
     end
     page = result(nil, 'rows' => 'version_no', 'cols' => '')
     values = page[:row_headers].select { _1[:kind] == 'data' }.map { _1[:values].first }
-    expect(values.map(&:to_i)).to eq([1, 2, 10])
+    expect(values.reject { _1 == CountsAxes::MASKED_VALUE }.map(&:to_i)).to eq([1, 2, 10])
+    expect(values.last).to eq(CountsAxes::MASKED_VALUE)
   end
 
-  it 'keeps public identity predicates and excludes private attributes' do
-    hidden_id = PostVersion.first.post_id.to_s
-    base = { 'rows' => '', 'cols' => '' }
-    condition = lambda do |field, operator, value|
-      { 'conditions' => '', 'conditions.0.field' => field,
-        'conditions.0.operator' => operator, 'conditions.0.value' => value }
-    end
-
-    expect(result(nil, base.merge('resource_id' => hidden_id))[:cells].sole[:count]).to eq(2)
-    expect(result(nil, base.merge(condition.call('version_no', 'eq', '2')))[:cells]
-        .sole[:count]).to eq(2)
-    expect(result(nil, base.merge(condition.call('user', 'eq', member.id.to_s)))[:cells]
-        .sole[:count]).to eq(5)
-    expect(result(nil, base.merge(condition.call('title', 'eq', 'hidden-title-0')))[:cells]
-        .sole[:count]).to eq(0)
-    expect(result(nil, base.merge(condition.call('title', 'ne', 'hidden-title-0')))[:cells]
-        .sole[:count]).to eq(1)
-    expect(result(nil, base.merge(condition.call('title', 'eq', '********')))[:cells]
-        .sole[:count]).to eq(0)
-    expect(result(nil, base.merge(condition.call('video_ms', 'eq', '********')))[:cells]
-        .sole[:count]).to eq(0)
-    expect(result(nil, base.merge(condition.call('title', 'like', '%title%')))[:cells]
-        .sole[:count]).to eq(1)
-    expect(result(nil, base.merge(condition.call('title', 'like', '%')))[:cells]
-        .sole[:count]).to eq(1)
-    expect(result(nil, base.merge('tags' => 'C'))[:cells].sole[:count]).to eq(1)
-    expect(result(nil, base.merge('tags' => 'not:C'))[:cells].sole[:count]).to eq(0)
-  end
-
-  it 'retains public OR branches while rejecting private predicates on hidden rows' do
-    HistoryAccess.set(user: nil) do
-      population = CountsPopulation.new(params.merge('rows' => '', 'cols' => ''),
-          authorisation_flg: false)
-      condition = CountsCondition.new(population)
-      public_scope = condition.apply(population.scope,
-          { 'field' => 'event_type', 'operator' => 'eq', 'value' => 'discard' })
-      private_scope = condition.apply(population.scope,
-          { 'field' => 'title', 'operator' => 'ne', 'value' => 'unrelated' })
-      masked_scope = condition.apply(population.scope,
-          { 'field' => 'title', 'operator' => 'eq', 'value' => '********' })
-      expect(public_scope.except(:select).count).to eq(2)
-      expect(public_scope.or(private_scope).except(:select).count).to eq(3)
-      expect(private_scope.or(public_scope).except(:select).count).to eq(3)
-      expect(public_scope.or(masked_scope).except(:select).count).to eq(2)
-      expect(public_scope.merge(private_scope).except(:select).count).to eq(0)
-    end
-  end
-
-  it 'excludes private collections from positive, negative, AND and OR tag searches' do
-    settings = { 'rows' => '', 'cols' => '' }
-    { 'C' => 1, 'not:C' => 0, 'not:unknown' => 1, '********' => 0,
-      'not:********' => 1, 'not:C C' => 0, 'not:C type:or C' => 1 }.each do |value, count|
-      expect(result(nil, settings.merge('tags' => value))[:cells].sole[:count]).to eq(count)
-    end
-  end
-
-  it 'ignores empty numeric and interval bounds without restricting private history' do
-    settings = { 'rows' => '', 'cols' => '', 'conditions' => '' }
-    { 'video_ms' => ['eq', 'ne', 'gt', 'ge', 'lt', 'le', 'range'],
-      'tags.sections' => ['range'] }.each do |field, operators|
-      operators.each do |operator|
-        condition = settings.merge('conditions.0.field' => field,
-            'conditions.0.operator' => operator)
-        empty = condition.merge('conditions.0.value' => '')
-        expect(result(nil, condition)[:cells].sole[:count]).to eq(5)
-        expect(result(nil, empty)[:cells].sole[:count]).to eq(5)
-        expect(result(nil, empty.merge('conditions.0.blank' => '0'))[:cells]
-            .sole[:count]).to eq(5)
-        if operator == 'range'
-          empty['conditions.0.end'] = ''
-          expect(result(nil, empty)[:cells].sole[:count]).to eq(5)
-          ['conditions.0.value', 'conditions.0.end'].each do |key|
-            active = empty.merge(key => '100')
-            expect(result(nil, active)[:cells].sole[:count]).to eq(0)
-          end
-        end
-      end
-    end
-  end
-
-  it 'keeps typed marker sets active after incompatible marker values are removed' do
-    settings = { 'rows' => '', 'cols' => '', 'conditions' => '',
-                 'conditions.0.field' => 'video_ms', 'conditions.0.values' => '1',
-                 'condition_values' => '', 'condition_values.0.condition' => '0',
-                 'condition_values.0.value_type' => 'string',
-                 'condition_values.0.value' => '********' }
-    ['in', 'not_in'].each do |operator|
-      expected = operator == 'in' ? 0 : 1
-      condition = settings.merge('conditions.0.operator' => operator)
-      expect(result(nil, condition)[:cells].sole[:count]).to eq(expected)
-    end
-  end
-
-  it 'restricts active numeric comparisons and preserves empty selection semantics' do
-    settings = { 'rows' => '', 'cols' => '', 'conditions' => '',
-                 'conditions.0.field' => 'video_ms' }
-    ['eq', 'ne', 'gt', 'ge', 'lt', 'le', 'range'].each do |operator|
-      condition = settings.merge('conditions.0.operator' => operator,
-          'conditions.0.value' => '0')
-      condition['conditions.0.end'] = '100' if operator == 'range'
-      # The one public row is NULL; private NULLs and real values never match.
-      expected = operator == 'ne' ? 1 : 0
-      expect(result(nil, condition)[:cells].sole[:count]).to eq(expected)
-    end
-    ['in', 'not_in'].each do |operator|
-      condition = settings.merge('conditions.0.operator' => operator,
-          'conditions.0.values' => '1', 'condition_values' => '')
-      expected = operator == 'not_in' ? 5 : 0
-      expect(result(nil, condition)[:cells].sole[:count]).to eq(expected)
-    end
-    blank = settings.merge('conditions.0.operator' => 'eq', 'conditions.0.blank' => '1')
-    expect(result(nil, blank)[:cells].sole[:count]).to eq(1)
-  end
-
-  it 'preserves empty tag sets and restricts active blank collection predicates' do
-    settings = { 'rows' => '', 'cols' => '', 'conditions' => '',
-                 'conditions.0.field' => 'tags' }
-    ['any', 'all', 'none'].each do |operator|
-      condition = settings.merge('conditions.0.operator' => operator,
-          'conditions.0.values' => '1', 'condition_values' => '')
-      expected = operator == 'any' ? 0 : 5
-      expect(result(nil, condition)[:cells].sole[:count]).to eq(expected)
-    end
-    blank = settings.merge('conditions.0.operator' => 'eq', 'conditions.0.blank' => '1')
-    expect(result(nil, blank)[:cells].sole[:count]).to eq(0)
-  end
-
-  it 'rejects server-only coordinates in column order' do
-    probes = [
+  it 'rejects private predicates and supplied measure coordinates before SQL labels escape' do
+    probes = [{ 'resource_id' => PostVersion.first.post_id.to_s },
+        { 'tags' => 'A' },
+        { 'conditions' => '', 'conditions.0.field' => 'title', 'conditions.0.operator' => 'eq',
+          'conditions.0.value' => 'hidden-title-0' },
+        { 'drill' => '', 'drill.0.field' => 'tags', 'drill.0.value_type' => 'string',
+          'drill.0.value' => "internal:#{ tags.first.id }" },
         { 'cols' => 'tags', 'column_order' => '', 'column_order.0.value_type' => 'string',
           'column_order.0.value' => CountsAxes::MASKED_VALUE }]
     HistoryAccess.set(user: nil) do
       probes.each do |probe|
-        expect { CountsTableQuery.new(params.merge(probe)).call }
+        expect { CountsTableQuery.new(params.merge(probe)) }
             .to raise_error(CountsAxes::PrivateCondition)
       end
     end
   end
 
-
-  it 'keeps private collection and change counts independent of stored elements' do
-    settings = [
-        { 'rows' => 'tags', 'cols' => 'changed_field' },
-        { 'rows' => 'changed_field tags', 'cols' => '' }]
-    original = settings.map { result(nil, _1) }
-    snapshot = tags.map do |tag|
-      { tag_id: tag.id, version_no: 1, sections: [] }
-    end
-    hidden_posts = PostVersion.where(event_type: 'discard').pluck(:post_id)
-    PostVersion.where(post_id: hidden_posts).update_all(
-        title: 'same hidden value', tags_json: snapshot)
-    expect(settings.map { result(nil, _1) }).to eq(original)
-  end
-
-  it 'excludes private tag and change coordinates from drill conditions' do
-    ['tags', 'changed_field'].each do |field|
-      settings = { 'rows' => field, 'cols' => '' }
-      page = result(nil, settings)
-      cell = page[:cells].find { _1[:values] == [CountsAxes::MASKED_VALUE] }
-      expect(cell[:count]).to eq(4)
-      [CountsAxes::MASKED_VALUE, CountsAxes::MASKED_TEXT].each do |value|
-        drill = { 'drill' => '', 'drill.0.field' => field,
-                  'drill.0.value_type' => 'string', 'drill.0.value' => value }
-        expect(result(nil, settings.merge(drill))[:cells]).to be_empty
-        details = result(nil, settings.merge(drill).merge('mode' => 'details'))
-        expect(details[:versions]).to be_empty
-        condition = { 'conditions' => '', 'conditions.0.field' => field,
-                      'conditions.0.operator' => 'axis_eq',
-                      'conditions.0.value_type' => 'string', 'conditions.0.value' => value }
-        expect(result(nil, settings.merge(condition))[:cells]).to be_empty
-      end
-    end
-  end
-
-  it 'rejects real private tag and change coordinates for non-admin users' do
-    [nil, guest, member].each do |user|
-      { 'tags' => "internal:#{ tags.first.id }", 'changed_field' => 'title' }.each do
-          |field, value|
-        settings = { 'rows' => '', 'cols' => '', 'drill' => '',
-                     'drill.0.field' => field, 'drill.0.value_type' => 'string',
-                     'drill.0.value' => value }
-        expect(result(user, settings)[:cells].sole[:count]).to eq(0)
-        expect(result(admin, settings)[:cells].sole[:count]).to be > 0
-      end
-    end
-  end
-
   it 'keeps public column sorting usable while guessed private coordinates match nothing' do
     first = result(nil, 'rows' => 'event_type', 'cols' => 'tags')
     probe = result(nil, 'rows' => 'event_type', 'cols' => 'tags',
@@ -357,7 +187,7 @@ RSpec.describe 'Counts masked pivot contracts' do
     HistoryAccess.set(user: nil) do
       payload = params.merge('format' => 'json')
       json = JSON.parse(CountsTableExport.new(payload).body.to_a.join)
-      expect(json['data'].sum { _1['kind'] == 'data' ? _1['count'] : 0 }).to eq(6)
+      expect(json['data'].sum { _1['kind'] == 'data' ? _1['count'] : 0 }).to eq(5)
       expect(json.to_json).not_to include('hidden-title', 'private-discard')
       csv = CountsTableExport.new(payload.merge('format' => 'csv')).body.to_a.join
       expect(csv).to include('********')

frontend/src/components/PostFormTagsArea.test.tsx

@@ -12,36 +12,24 @@ const api = vi.hoisted (() => ({
 vi.mock ('@/lib/api', () => api)
 
 describe ('PostFormTagsArea', () => {
-  it ('replaces the selected token and restores the caret without losing other tags', async () => {
+  it ('updates text and fetches autocomplete for the selected token', async () => {
     const setTags = vi.fn ()
     api.apiGet.mockResolvedValueOnce ([buildTag ({ name: '虹夏', postCount: 3 })])
 
-    const { rerender } = renderWithProviders (
-	<PostFormTagsArea tags="ぼっち 虹 後続" setTags={setTags}/>)
+    renderWithProviders (<PostFormTagsArea tags="虹" setTags={setTags}/>)
 
-    const textarea = screen.getByRole<HTMLTextAreaElement> ('textbox')
+    const textarea = screen.getByRole ('textbox')
     fireEvent.focus (textarea)
-    fireEvent.change (textarea, { target: { value: 'ぼっち 虹な 後続' } })
-    rerender (<PostFormTagsArea tags="ぼっち 虹な 後続" setTags={setTags}/>)
-    fireEvent.select (textarea, { target: { selectionStart: 6, selectionEnd: 6 } })
+    fireEvent.select (textarea, { target: { selectionStart: 1, selectionEnd: 1 } })
+    fireEvent.change (textarea, { target: { value: '虹夏' } })
 
     await waitFor (() => {
       expect (api.apiGet).toHaveBeenCalledWith (
-	  '/tags/autocomplete', {
-	      locale: 'ja', params: { q: '虹な', nico: '0' },
-	      signal: expect.any (AbortSignal) })
+          '/tags/autocomplete',
+          { locale: 'ja', params: { q: '虹', nico: '0' },
+	    signal: expect.any (AbortSignal) },
+      )
     })
-    expect (setTags).toHaveBeenCalledWith ('ぼっち 虹な 後続')
-
-    fireEvent.mouseDown (await screen.findByText ('虹夏'))
-    expect (setTags).toHaveBeenLastCalledWith ('ぼっち 虹夏  後続')
-    rerender (<PostFormTagsArea tags="ぼっち 虹夏  後続" setTags={setTags}/>)
-
-    await waitFor (() => {
-      expect (textarea).toHaveFocus ()
-      expect (textarea.selectionStart).toBe (7)
-      expect (textarea.selectionEnd).toBe (7)
-    })
-    expect (screen.queryByText ('虹夏')).not.toBeInTheDocument ()
+    expect (setTags).toHaveBeenCalledWith ('虹夏')
   })
 })

frontend/src/components/PostFormTagsArea.tsx

@@ -1,10 +1,13 @@
-import { useRef, useState } from 'react'
+// TODO: TagSearch と共通化する．
 
-import { useTagAutocomplete } from '@/lib/useTagAutocomplete'
+import { useEffect, useRef, useState } from 'react'
+
+import { useLocale } from '@/lib/useLocale'
 import { useUITranslation } from '@/lib/useUITranslation'
 import TagSearchBox from '@/components/TagSearchBox'
 import FormField from '@/components/common/FormField'
 import TextArea from '@/components/common/TextArea'
+import { apiGet } from '@/lib/api'
 
 import type { ComponentPropsWithoutRef, FC, ReactNode, SyntheticEvent } from 'react'
 
@@ -38,13 +41,24 @@ type Props = Omit<ComponentPropsWithoutRef<'textarea'>, 'value' | 'onChange' | '
 
 const PostFormTagsArea: FC<Props> = ({ tags, setTags, errors, ...rest }) => {
   const { label } = useUITranslation ('navigation')
+  const locale = useLocale ()
   const ref = useRef<HTMLTextAreaElement> (null)
 
   const [bounds, setBounds] = useState<{ start: number; end: number }> ({ start: 0, end: 0 })
   const [focused, setFocused] = useState (false)
+  const [request, setRequest] = useState ({ query: '' })
+  const [result, setResult] = useState<{
+      locale: string
+      request: { query: string }
+      tags: Tag[] }> ({ locale, request, tags: [] })
   const currentToken = getTokenAt (tags, Math.min (bounds.start, tags.length)).token
+  const suggestions = (result.locale === locale && result.request === request
+      && request.query === currentToken) ? result.tags : []
+  const [suggestionsVsbl, setSuggestionsVsbl] = useState (false)
 
   const handleTagSelect = (tag: Tag) => {
+    setSuggestionsVsbl (false)
+    setRequest ({ query: '' })
     const textarea = ref.current!
     const newValue = replaceToken (tags, bounds.start, bounds.end, tag.name + ' ')
     setTags (newValue)
@@ -56,18 +70,52 @@ const PostFormTagsArea: FC<Props> = ({ tags, setTags, errors, ...rest }) => {
     })
   }
 
-  const { inputProps, suggestionProps, requestSuggestions } =
-      useTagAutocomplete ({ token: currentToken, onSelect: handleTagSelect })
-
   const recompute = (pos: number, v: string = tags) => {
     const { start, end, token } = getTokenAt (v, pos)
-    requestSuggestions (token)
+    setRequest ({ query: token })
+    setSuggestionsVsbl (token.trim () !== '')
     if (!(token.trim ()))
-      return
+      {
+	setSuggestionsVsbl (false)
+	return
+      }
 
     setBounds ({ start, end })
   }
 
+  useEffect (() => {
+    if (request.query.trim () === '')
+      return
+    const controller = new AbortController ()
+    let active = true
+    void (async () => {
+      try
+      {
+	const tags = await apiGet<Tag[]> ('/tags/autocomplete', {
+	    locale, signal: controller.signal, params: { q: request.query, nico: '0' } })
+	if (active)
+	{
+	  setResult ({ locale, request,
+	      tags: tags.filter (tag => tag.postCount > 0) })
+	}
+      }
+      catch
+      {
+	if (active)
+	  setResult ({ locale, request, tags: [] })
+      }
+    }) ()
+    return () => {
+      active = false
+      controller.abort ()
+    }
+  }, [request, locale])
+
+  useEffect (() => {
+    setSuggestionsVsbl (false)
+    setRequest ({ query: '' })
+  }, [locale])
+
   return (
       <FormField className="relative w-full" label={label ('tags')} messages={errors}>
 	{({ describedBy, invalid }) => (
@@ -86,10 +134,15 @@ const PostFormTagsArea: FC<Props> = ({ tags, setTags, errors, ...rest }) => {
 		  onFocus={() => setFocused (true)}
 		  onBlur={() => {
 		    setFocused (false)
-		    inputProps.onBlur ()
+		    setSuggestionsVsbl (false)
 		  }}/>
 	      {focused && (
-		  <TagSearchBox {...suggestionProps}/>)}
+		  <TagSearchBox
+		      suggestions={suggestionsVsbl && suggestions.length > 0
+				   ? suggestions
+				   : [] as Tag[]}
+		      activeIndex={-1}
+		      onSelect={handleTagSelect}/>)}
 	    </>)}
       </FormField>)
 }

frontend/src/components/TagSearch.test.tsx

@@ -1,157 +0,0 @@
-import { act, fireEvent, screen } from '@testing-library/react'
-import userEvent from '@testing-library/user-event'
-import { useLocation } from 'react-router-dom'
-import { beforeEach, describe, expect, it, vi } from 'vitest'
-
-import TagSearch from '@/components/TagSearch'
-import * as api from '@/lib/api'
-import { buildTag } from '@/test/factories'
-import { renderWithProviders } from '@/test/render'
-
-import type { Tag } from '@/types'
-
-
-const LocationOutput = () => {
-  const location = useLocation ()
-  return <output data-testid="location">{location.pathname}{location.search}</output>
-}
-
-
-const renderSearch = () => renderWithProviders (
-    <>
-      <TagSearch/>
-      <LocationOutput/>
-    </>, { route: '/ja/posts?page=3' })
-
-
-describe ('TagSearch', () => {
-  beforeEach (() => {
-    vi.spyOn (api, 'apiGet').mockResolvedValue ([])
-  })
-
-  it ('searches through native submission without an Enter key event', () => {
-    renderSearch ()
-    const input = screen.getByRole<HTMLInputElement> ('textbox')
-    fireEvent.change (input, { target: { value: '虹夏 not:TEST type:or' } })
-
-    expect (input.form).toBeInstanceOf (HTMLFormElement)
-    fireEvent.submit (input.form!)
-
-    const query = new URLSearchParams ({ tags: '虹夏 not:test', match: 'any' })
-    expect (screen.getByTestId ('location')).toHaveTextContent (
-	`/ja/posts?${ query }`)
-    expect (input).toHaveValue ('虹夏 not:test type:or')
-  })
-
-  it ('requests a search action from the software keyboard', () => {
-    renderSearch ()
-
-    expect (screen.getByRole ('textbox')).toHaveAttribute ('enterkeyhint', 'search')
-  })
-
-  it ('searches through the form when Enter is pressed', async () => {
-    const user = userEvent.setup ()
-    renderSearch ()
-
-    await user.type (screen.getByRole ('textbox'), '虹夏{Enter}')
-
-    const query = new URLSearchParams ({ tags: '虹夏', match: 'all' })
-    expect (screen.getByTestId ('location')).toHaveTextContent (
-	`/ja/posts?${ query }`)
-  })
-
-  it.each ([
-      { label: 'composition flag', composing: true, keyCode: 13 },
-      { label: 'legacy IME code', composing: false, keyCode: 229 }]) (
-      'cancels confirmation Enter with $label', ({ composing, keyCode }) => {
-    renderSearch ()
-    const input = screen.getByRole ('textbox')
-    fireEvent.change (input, { target: { value: '虹夏' } })
-    const uncancelled = fireEvent.keyDown (input, {
-	key: 'Enter', isComposing: composing, keyCode })
-
-    expect (uncancelled).toBe (false)
-    expect (screen.getByTestId ('location')).toHaveTextContent ('/ja/posts?page=3')
-    expect (input).toHaveValue ('虹夏')
-  })
-
-  it ('cancels Enter throughout composition even without keyboard IME flags', () => {
-    renderSearch ()
-    const input = screen.getByRole ('textbox')
-    fireEvent.compositionStart (input)
-    fireEvent.change (input, { target: { value: '虹夏' } })
-    const uncancelled = fireEvent.keyDown (input, {
-	key: 'Enter', isComposing: false, keyCode: 13 })
-
-    expect (uncancelled).toBe (false)
-    expect (screen.getByTestId ('location')).toHaveTextContent ('/ja/posts?page=3')
-    expect (input).toHaveValue ('虹夏')
-  })
-
-  it ('blocks direct submission during composition and allows it after confirmation', () => {
-    renderSearch ()
-    const input = screen.getByRole<HTMLInputElement> ('textbox')
-    fireEvent.compositionStart (input)
-    fireEvent.change (input, { target: { value: '虹夏' } })
-    fireEvent.submit (input.form!)
-
-    expect (screen.getByTestId ('location')).toHaveTextContent ('/ja/posts?page=3')
-    expect (input).toHaveValue ('虹夏')
-
-    fireEvent.compositionEnd (input)
-    fireEvent.submit (input.form!)
-
-    const query = new URLSearchParams ({ tags: '虹夏', match: 'all' })
-    expect (screen.getByTestId ('location')).toHaveTextContent (
-	`/ja/posts?${ query }`)
-  })
-
-  it ('selects the active suggestion without submitting the form', async () => {
-    vi.mocked (api.apiGet).mockResolvedValue ([buildTag ({ name: '虹夏' })])
-    const user = userEvent.setup ()
-    renderSearch ()
-
-    await user.type (screen.getByRole ('textbox'), '虹')
-    await screen.findByText ('虹夏')
-    await user.keyboard ('{ArrowDown}{Enter}')
-
-    expect (screen.getByRole ('textbox')).toHaveValue ('虹夏 ')
-    expect (screen.getByTestId ('location')).toHaveTextContent ('/ja/posts?page=3')
-    expect (screen.queryByText ('虹夏')).not.toBeInTheDocument ()
-  })
-
-  it ('aborts obsolete requests and ignores their late suggestions', async () => {
-    const responses: ((tags: Tag[]) => void)[] = []
-    vi.mocked (api.apiGet).mockImplementation (() => new Promise<Tag[]> (resolve => {
-      responses.push (resolve)
-    }))
-    const { unmount } = renderSearch ()
-    const input = screen.getByRole ('textbox')
-
-    fireEvent.change (input, { target: { value: '虹' } })
-    const previousSignal = vi.mocked (api.apiGet).mock.calls.at (-1)?.[1]?.signal
-    expect (previousSignal).toBeInstanceOf (AbortSignal)
-    expect (previousSignal?.aborted).toBe (false)
-
-    fireEvent.change (input, { target: { value: 'ぼ' } })
-    expect (previousSignal?.aborted).toBe (true)
-    expect (api.apiGet).toHaveBeenLastCalledWith ('/tags/autocomplete', {
-	locale: 'ja', params: { q: 'ぼ', nico: '1' },
-	signal: expect.any (AbortSignal) })
-    const currentSignal = vi.mocked (api.apiGet).mock.calls.at (-1)?.[1]?.signal
-
-    await act (async () => {
-      responses[1] ([buildTag ({ name: 'ぼっち' })])
-    })
-    expect (screen.getByText ('ぼっち')).toBeInTheDocument ()
-
-    await act (async () => {
-      responses[0] ([buildTag ({ name: '虹夏' })])
-    })
-    expect (screen.queryByText ('虹夏')).not.toBeInTheDocument ()
-    expect (screen.getByText ('ぼっち')).toBeInTheDocument ()
-
-    unmount ()
-    expect (currentSignal?.aborted).toBe (true)
-  })
-})

frontend/src/components/TagSearch.tsx

@@ -1,59 +1,136 @@
+// TODO: タグ入力系すべてに同様の処理あるため共通化する．
+
 import { useEffect, useState } from 'react'
 import { useLocation } from 'react-router-dom'
 
-import TagSearchBox from '@/components/TagSearchBox'
-import { useLocaleNavigate } from '@/lib/useLocale'
-import { useTagAutocomplete } from '@/lib/useTagAutocomplete'
+import { useLocale, useLocaleNavigate } from '@/lib/useLocale'
 import { useUITranslation } from '@/lib/useUITranslation'
+import { apiGet } from '@/lib/api'
 import { inputClass } from '@/lib/utils'
 
-import type { ChangeEvent, FC, FormEvent } from 'react'
+import TagSearchBox from './TagSearchBox'
+
+import type { ChangeEvent, FC, KeyboardEvent } from 'react'
 
 import type { Tag } from '@/types'
 
 
 const TagSearch: FC = () => {
   const { message } = useUITranslation ('shared')
+  const locale = useLocale ()
   const location = useLocation ()
   const navigate = useLocaleNavigate ()
+
+  const [activeIndex, setActiveIndex] = useState (-1)
   const [search, setSearch] = useState ('')
+  const [request, setRequest] = useState ({ query: '' })
+  const [result, setResult] = useState<{
+      locale: string
+      request: { query: string }
+      tags: Tag[] }> ({ locale, request, tags: [] })
+  const suggestions = result.locale === locale && result.request === request
+      ? result.tags : []
+  const [suggestionsVsbl, setSuggestionsVsbl] = useState (false)
+
+  const whenChanged = (ev: ChangeEvent<HTMLInputElement>) => {
+    const value = ev.target.value
+    const query = value.trim ().split (' ').at (-1) ?? ''
+    setSearch (value)
+    setRequest ({ query })
+    setActiveIndex (-1)
+    setSuggestionsVsbl (query !== '')
+  }
+
+  useEffect (() => {
+    if (request.query === '')
+      return
+    const controller = new AbortController ()
+    let active = true
+    void (async () => {
+      try
+      {
+	const tags = await apiGet<Tag[]> ('/tags/autocomplete', {
+	    locale, signal: controller.signal, params: { q: request.query } })
+	if (active)
+	{
+	  setResult ({ locale, request,
+	      tags: tags.filter (tag => tag.postCount > 0) })
+	}
+      }
+      catch
+      {
+	if (active)
+	  setResult ({ locale, request, tags: [] })
+      }
+    }) ()
+    return () => {
+      active = false
+      controller.abort ()
+    }
+  }, [request, locale])
+
+  useEffect (() => {
+    setActiveIndex (-1)
+    setSuggestionsVsbl (false)
+  }, [locale])
+
+  const handleKeyDown = (ev: KeyboardEvent<HTMLInputElement>) => {
+    switch (ev.key)
+    {
+    case 'ArrowDown':
+      ev.preventDefault ()
+      setActiveIndex (i => Math.min (i + 1, suggestions.length - 1))
+      setSuggestionsVsbl (true)
+      break
+
+    case 'ArrowUp':
+      ev.preventDefault ()
+      setActiveIndex (i => Math.max (i - 1, -1))
+      setSuggestionsVsbl (true)
+      break
+
+    case 'Enter':
+      if (activeIndex < 0)
+	break
+      ev.preventDefault ()
+      {
+	const selected = suggestions[activeIndex]
+	if (selected)
+	  handleTagSelect (selected)
+      }
+      break
+
+    case 'Escape':
+      ev.preventDefault ()
+      setSuggestionsVsbl (false)
+      break
+    }
+    if (ev.key === 'Enter' && (!(suggestionsVsbl) || activeIndex < 0))
+      {
+	const parts = search.split (' ')
+	const match = parts.map (t => t.toLowerCase ()).includes ('type:or') ? 'any' : 'all'
+	navigate (`/posts?${
+	    (new URLSearchParams ({
+		tags: parts.map (t => t.toLowerCase ())
+			   .filter (t => t !== 'type:or')
+			   .join (' '),
+		match }))
+	    .toString () }`)
+	setSuggestionsVsbl (false)
+	setRequest ({ query: '' })
+      }
+  }
 
   const handleTagSelect = (tag: Tag) => {
     const parts = search.split (' ')
     parts[parts.length - 1] = (
-	(parts[parts.length - 1].slice (0, 4).toLowerCase () === 'not:')
+	(parts[parts.length - 1].slice(0, 4).toLowerCase () === 'not:')
 	? ('not:' + tag.name)
 	: tag.name)
     setSearch (parts.join (' ') + ' ')
-  }
-
-  const { inputProps, suggestionProps, requestSuggestions,
-	  clearSuggestions, compositionFlgRef } = useTagAutocomplete ({
-      token: search.trim ().split (' ').at (-1) ?? '',
-      nicoFlg: true,
-      onSelect: handleTagSelect })
-
-  const whenChanged = (event: ChangeEvent<HTMLInputElement>) => {
-    const value = event.target.value
-    setSearch (value)
-    requestSuggestions (value.trim ().split (' ').at (-1) ?? '')
-  }
-
-  const handleSubmit = (event: FormEvent<HTMLFormElement>) => {
-    event.preventDefault ()
-    if (compositionFlgRef.current)
-      return
-
-    const parts = search.split (' ')
-    const match =
-	parts.map (t => t.toLowerCase ()).includes ('type:or') ? 'any' : 'all'
-    navigate (`/posts?${
-	(new URLSearchParams ({
-	    tags: parts.map (t => t.toLowerCase ())
-		       .filter (t => t !== 'type:or')
-		       .join (' '),
-	    match })).toString () }`)
-    clearSuggestions ()
+    setRequest ({ query: '' })
+    setSuggestionsVsbl (false)
+    setActiveIndex (-1)
   }
 
   useEffect (() => {
@@ -61,22 +138,27 @@ const TagSearch: FC = () => {
     const anyFlg = query.get ('match') === 'any'
     const tagsQuery = `${ query.get ('tags') ?? '' }${ anyFlg ? ' type:or' : '' }`
     setSearch (tagsQuery)
-    clearSuggestions ()
-  }, [location.search, clearSuggestions])
+    setRequest ({ query: '' })
+    setActiveIndex (-1)
+    setSuggestionsVsbl (false)
+  }, [location.search])
 
   return (
-      <form onSubmit={handleSubmit} className="relative w-full">
+      <div className="relative w-full">
 	<input type="text"
-	       {...inputProps}
-	       enterKeyHint="search"
 	       data-shortcut-focus-search="true"
 	       placeholder={message ('labels.tagSearch').text}
 	       value={search}
 	       onChange={whenChanged}
+	       onFocus={() => setSuggestionsVsbl (true)}
+	       onBlur={() => setSuggestionsVsbl (false)}
+	       onKeyDown={handleKeyDown}
 	       className={inputClass (false,
 				      'px-3 py-2 dark:border-gray-600 dark:bg-gray-800 dark:text-white')}/>
-	<TagSearchBox {...suggestionProps}/>
-      </form>)
+	<TagSearchBox suggestions={suggestionsVsbl && suggestions.length ? suggestions : [] as Tag[]}
+		      activeIndex={activeIndex}
+		      onSelect={handleTagSelect}/>
+      </div>)
 }
 
 export default TagSearch

frontend/src/components/common/TagInput.test.tsx

@@ -1,4 +1,4 @@
-import { act, fireEvent, screen, waitFor } from '@testing-library/react'
+import { fireEvent, screen, waitFor } from '@testing-library/react'
 import { beforeEach, describe, expect, it, vi } from 'vitest'
 
 import TagInput from '@/components/common/TagInput'
@@ -20,20 +20,18 @@ describe ('TagInput', () => {
     const setValue = vi.fn ()
     api.apiGet.mockResolvedValueOnce ([buildTag ({ name: '虹夏', postCount: 2 })])
 
-    const { rerender } = render (
-	<TagInput value="ぼっち 虹" setValue={setValue}/>)
+    render (<TagInput value="ぼっち 虹" setValue={setValue}/>)
 
     fireEvent.change (screen.getByRole ('textbox'), { target: { value: 'ぼっち 虹夏' } })
-    rerender (<TagInput value="ぼっち 虹夏" setValue={setValue}/>)
 
     await waitFor (() => {
       expect (api.apiGet).toHaveBeenCalledWith (
-	  '/tags/autocomplete', {
-	      locale: 'ja', params: { q: '虹夏', nico: '0' },
-	      signal: expect.any (AbortSignal) })
+          '/tags/autocomplete',
+          { locale: 'ja', params: { q: '虹夏', nico: '0' },
+	    signal: expect.any (AbortSignal) },
+      )
     })
     expect (setValue).toHaveBeenCalledWith ('ぼっち 虹夏')
-    expect (await screen.findByText ('虹夏')).toBeInTheDocument ()
   })
 
   it ('does not fetch when the last token is blank', () => {
@@ -56,51 +54,10 @@ describe ('TagInput', () => {
 
     await waitFor (() => {
       expect (api.apiGet).toHaveBeenCalledWith (
-	  '/tags/autocomplete', {
-	      locale: 'ja', params: { q: '虹夏', nico: '1' },
-	      signal: expect.any (AbortSignal) })
+          '/tags/autocomplete',
+          { locale: 'ja', params: { q: '虹夏', nico: '1' },
+	    signal: expect.any (AbortSignal) },
+      )
     })
   })
-
-  it ('preserves negation and blocks suggestion selection during composition', async () => {
-    const setValue = vi.fn ()
-    api.apiGet.mockResolvedValueOnce ([buildTag ({ name: '虹夏' })])
-    const { rerender } = render (<TagInput value="" setValue={setValue}/>)
-    const input = screen.getByRole ('textbox')
-
-    fireEvent.change (input, { target: { value: 'ぼっち NOT:虹' } })
-    rerender (<TagInput value="ぼっち NOT:虹" setValue={setValue}/>)
-    await screen.findByText ('虹夏')
-    expect (api.apiGet).toHaveBeenLastCalledWith (
-	'/tags/autocomplete', {
-	    locale: 'ja', params: { q: '虹', nico: '0' },
-	    signal: expect.any (AbortSignal) })
-
-    fireEvent.keyDown (input, { key: 'ArrowDown' })
-    fireEvent.compositionStart (input)
-    expect (fireEvent.keyDown (input, { key: 'Enter' })).toBe (false)
-    expect (setValue).toHaveBeenCalledTimes (1)
-
-    fireEvent.compositionEnd (input)
-    fireEvent.keyDown (input, { key: 'Enter' })
-
-    expect (setValue).toHaveBeenLastCalledWith ('ぼっち not:虹夏 ')
-    expect (screen.queryByText ('虹夏')).not.toBeInTheDocument ()
-  })
-
-  it.each ([false, true]) ('includes unused tags only with includeUnused=%s', async unusedFlg => {
-    const tag = buildTag ({ name: '虹夏', postCount: 0 })
-    const response = Promise.resolve ([tag])
-    api.apiGet.mockReturnValueOnce (response)
-    const props = { setValue: vi.fn (), includeUnused: unusedFlg }
-    const { rerender } = render (<TagInput {...props} value=""/>)
-
-    fireEvent.change (screen.getByRole ('textbox'), { target: { value: '虹' } })
-    rerender (<TagInput {...props} value="虹"/>)
-    await act (async () => {
-      await response
-    })
-
-    expect (screen.queryByText ('虹夏') != null).toBe (unusedFlg)
-  })
 })

frontend/src/components/common/TagInput.tsx

@@ -1,8 +1,11 @@
+import { useEffect, useState } from 'react'
+
+import { useLocale } from '@/lib/useLocale'
 import TagSearchBox from '@/components/TagSearchBox'
-import { useTagAutocomplete } from '@/lib/useTagAutocomplete'
+import { apiGet } from '@/lib/api'
 import { inputClass } from '@/lib/utils'
 
-import type { FC, ChangeEvent } from 'react'
+import type { FC, ChangeEvent, KeyboardEvent } from 'react'
 
 import type { Tag } from '@/types'
 
@@ -16,39 +19,136 @@ type Props = {
     setValue:      (value: string) => void }
 
 
-const TagInput: FC<Props> = (
-    { includeNico: nicoFlg = false,
-      includeUnused: unusedFlg = false,
-      describedBy, invalid, value, setValue },
-) => {
+const TagInput: FC<Props> = ({
+    includeNico = false,
+    includeUnused = false,
+    describedBy,
+    invalid,
+    value,
+    setValue,
+}) => {
+  const locale = useLocale ()
+  const [activeIndex, setActiveIndex] = useState (-1)
+  const [request, setRequest] = useState ({ query: '' })
+  const [result, setResult] = useState<{
+      locale: string
+      includeNico: boolean
+      request: { query: string }
+      tags: Tag[] }> ({ locale, includeNico, request, tags: [] })
+  const suggestions = (result.locale === locale && result.includeNico === includeNico
+      && result.request === request
+      && request.query === value.trim ().split (' ').at (-1)) ? result.tags : []
+  const [suggestionsVsbl, setSuggestionsVsbl] = useState (false)
+
+  // TODO: TagSearch からのコピペのため，共通化を考へる．
+  const whenChanged = (ev: ChangeEvent<HTMLInputElement>) => {
+    setValue (ev.target.value)
+    const query = ev.target.value.trim ().split (' ').at (-1) ?? ''
+    setRequest ({ query })
+    setActiveIndex (-1)
+    setSuggestionsVsbl (query !== '')
+  }
+
+  useEffect (() => {
+    if (request.query === '')
+      return
+    const controller = new AbortController ()
+    let active = true
+    void (async () => {
+      try
+      {
+	const tags = await apiGet<Tag[]> ('/tags/autocomplete', {
+	    locale, signal: controller.signal,
+	    params: { q: request.query.replace (/^not:/i, ''), nico: includeNico ? '1' : '0' } })
+	if (active)
+	{
+	  setResult ({ locale, includeNico, request,
+	      tags: includeUnused ? tags : tags.filter (tag => tag.postCount > 0) })
+	}
+      }
+      catch
+      {
+	if (active)
+	  setResult ({ locale, includeNico, request, tags: [] })
+      }
+    }) ()
+    return () => {
+      active = false
+      controller.abort ()
+    }
+  }, [request, locale, includeNico, includeUnused])
+
+  useEffect (() => {
+    setActiveIndex (-1)
+    setSuggestionsVsbl (false)
+    setRequest ({ query: '' })
+  }, [locale, includeNico])
+
+  // TODO: TagSearch からのコピペのため，共通化を考へる．
   const handleTagSelect = (tag: Tag) => {
     const parts = value?.split (' ')
     const negative = /^not:/i.test (parts[parts.length - 1])
     parts[parts.length - 1] = `${negative ? 'not:' : ''}${tag.name}`
     setValue (parts.join (' ') + ' ')
+    setRequest ({ query: '' })
+    setActiveIndex (-1)
   }
 
-  const { inputProps, suggestionProps, requestSuggestions } =
-      useTagAutocomplete ({ token: value.trim ().split (' ').at (-1) ?? '',
-			    nicoFlg, unusedFlg, onSelect: handleTagSelect })
+  // TODO: TagSearch からのコピペのため，共通化を考へる．
+  const handleKeyDown = (ev: KeyboardEvent<HTMLInputElement>) => {
+    switch (ev.key)
+    {
+    case 'ArrowDown':
+      ev.preventDefault ()
+      setActiveIndex (i => Math.min (i + 1, suggestions.length - 1))
+      setSuggestionsVsbl (true)
+      break
 
-  const whenChanged = (event: ChangeEvent<HTMLInputElement>) => {
-    setValue (event.target.value)
-    const token = event.target.value.trim ().split (' ').at (-1) ?? ''
-    requestSuggestions (token, token.replace (/^not:/i, ''))
+    case 'ArrowUp':
+      ev.preventDefault ()
+      setActiveIndex (i => Math.max (i - 1, -1))
+      setSuggestionsVsbl (true)
+      break
+
+    case 'Enter':
+      if (activeIndex < 0)
+	break
+      {
+	ev.preventDefault ()
+	const selected = suggestions[activeIndex]
+	if (selected)
+	  handleTagSelect (selected)
+      }
+      break
+
+    case 'Escape':
+      ev.preventDefault ()
+      setSuggestionsVsbl (false)
+      break
+    }
+    if (ev.key === 'Enter' && (!(suggestionsVsbl) || activeIndex < 0))
+      {
+	setSuggestionsVsbl (false)
+      }
   }
 
   return (
       <div className="relative">
 	<input
-	    {...inputProps}
 	    type="text"
 	    aria-describedby={describedBy}
 	    aria-invalid={invalid}
 	    value={value}
 	    onChange={whenChanged}
+	    onFocus={() => setSuggestionsVsbl (true)}
+	    onBlur={() => setSuggestionsVsbl (false)}
+	    onKeyDown={handleKeyDown}
 	    className={inputClass (invalid)}/>
-	<TagSearchBox {...suggestionProps}/>
+	<TagSearchBox
+	    suggestions={
+		suggestionsVsbl && suggestions.length > 0 ? suggestions : [] as Tag[]}
+	    activeIndex={activeIndex}
+	    onSelect={handleTagSelect}/>
       </div>)
 }
 

frontend/src/lib/tags.ts

@@ -11,17 +11,6 @@ import type { Deerjikist,
 	      TagVersion } from '@/types'
 
 
-export const fetchTagAutocomplete = async (
-    query: string,
-    nicoFlg: boolean,
-    locale: LocaleCode,
-    signal: AbortSignal,
-): Promise<Tag[]> =>
-    await apiGet ('/tags/autocomplete', {
-	locale, signal,
-	params: { q: query, nico: nicoFlg ? '1' : '0' } })
-
-
 export const fetchTags = async (
     { post, name, category, postCountGTE, postCountLTE, createdFrom, createdTo,
       updatedFrom, updatedTo, deprecated,

frontend/src/lib/useTagAutocomplete.ts

@@ -1,142 +0,0 @@
-import { useCallback, useEffect, useRef, useState } from 'react'
-
-import { fetchTagAutocomplete } from '@/lib/tags'
-import { useLocale } from '@/lib/useLocale'
-
-import type { KeyboardEvent } from 'react'
-
-import type { Tag } from '@/types'
-
-
-export const useTagAutocomplete = (
-    { token, onSelect, nicoFlg = false, unusedFlg = false }: {
-	token: string
-	onSelect: (tag: Tag) => void
-	nicoFlg?: boolean
-	unusedFlg?: boolean },
-) => {
-  const locale = useLocale ()
-  const compositionFlgRef = useRef (false)
-  const [activeIndex, setActiveIndex] = useState (-1)
-  const [visible, setVisible] = useState (false)
-  const [request, setRequest] = useState ({ token: '', query: '' })
-  const [result, setResult] = useState<{
-      locale: string
-      nicoFlg: boolean
-      unusedFlg: boolean
-      request: { token: string; query: string }
-      tags: Tag[] }> ({ locale, nicoFlg, unusedFlg, request, tags: [] })
-  const suggestions = (result.locale === locale && result.nicoFlg === nicoFlg
-      && result.unusedFlg === unusedFlg && result.request === request
-      && request.token === token) ? result.tags : []
-
-  const requestSuggestions = (token: string, query: string = token) => {
-    setRequest ({ token, query })
-    setActiveIndex (-1)
-    setVisible (token.trim () !== '')
-  }
-
-  const clearSuggestions = useCallback (() => {
-    setRequest ({ token: '', query: '' })
-    setActiveIndex (-1)
-    setVisible (false)
-  }, [])
-
-  useEffect (() => {
-    if (request.token.trim () === '')
-      return
-    const controller = new AbortController ()
-    let active = true
-    void (async () => {
-      try
-      {
-	const tags = await fetchTagAutocomplete (
-	    request.query, nicoFlg, locale, controller.signal)
-	if (active)
-	{
-	  setResult ({ locale, nicoFlg, unusedFlg, request,
-	      tags: unusedFlg ? tags : tags.filter (tag => tag.postCount > 0) })
-	}
-      }
-      catch
-      {
-	if (active)
-	  setResult ({ locale, nicoFlg, unusedFlg, request, tags: [] })
-      }
-    }) ()
-    return () => {
-      active = false
-      controller.abort ()
-    }
-  }, [request, locale, nicoFlg, unusedFlg])
-
-  useEffect (() => {
-    clearSuggestions ()
-  }, [locale, nicoFlg, clearSuggestions])
-
-  const handleTagSelect = (tag: Tag) => {
-    clearSuggestions ()
-    onSelect (tag)
-  }
-
-  const handleKeyDown = (event: KeyboardEvent<HTMLInputElement>) => {
-    if (compositionFlgRef.current
-	|| event.nativeEvent.isComposing
-	|| event.nativeEvent.keyCode === 229)
-    {
-      if (event.key === 'Enter')
-	event.preventDefault ()
-      return
-    }
-
-    switch (event.key)
-    {
-    case 'ArrowDown':
-      event.preventDefault ()
-      setActiveIndex (index => Math.min (index + 1, suggestions.length - 1))
-      setVisible (true)
-      break
-
-    case 'ArrowUp':
-      event.preventDefault ()
-      setActiveIndex (index => Math.max (index - 1, -1))
-      setVisible (true)
-      break
-
-    case 'Enter':
-      {
-	const selected = visible ? suggestions[activeIndex] : null
-	if (selected == null)
-	{
-	  setVisible (false)
-	  break
-	}
-	event.preventDefault ()
-	handleTagSelect (selected)
-      }
-      break
-
-    case 'Escape':
-      event.preventDefault ()
-      setVisible (false)
-      break
-    }
-  }
-
-  return {
-      requestSuggestions, clearSuggestions, compositionFlgRef,
-      inputProps: {
-	  onFocus: () => setVisible (true),
-	  onBlur: () => setVisible (false),
-	  onKeyDown: handleKeyDown,
-	  onCompositionStart: () => {
-	    compositionFlgRef.current = true
-	  },
-	  onCompositionEnd: () => {
-	    compositionFlgRef.current = false
-	  } },
-      suggestionProps: {
-	  suggestions: visible ? suggestions : [],
-	  activeIndex,
-	  onSelect: handleTagSelect } }
-}