Extract author filtering from issuable finder

This moves author filtering related code to a separate class

app/finders/issuable_finder.rb

@@ -47,6 +47,7 @@ class IssuableFinder
   NEGATABLE_PARAMS_HELPER_KEYS = %i[project_id scope status include_subgroups].freeze
 
   attr_accessor :current_user, :params
+  attr_reader :original_params
   attr_writer :parent
 
   delegate(*%i[assignee milestones], to: :params)
@@ -101,6 +102,7 @@ class IssuableFinder
 
   def initialize(current_user, params = {})
     @current_user = current_user
+    @original_params = params
     @params = params_class.new(params, current_user, klass)
   end
 
@@ -142,7 +144,7 @@ class IssuableFinder
   end
 
   def should_filter_negated_args?
-    return false unless Feature.enabled?(:not_issuable_queries, params.group || params.project, default_enabled: true)
+    return false unless not_filters_enabled?
 
     # API endpoints send in `nil` values so we test if there are any non-nil
     not_params.present? && not_params.values.any?
@@ -150,7 +152,6 @@ class IssuableFinder
 
   # Negates all params found in `negatable_params`
   def filter_negated_items(items)
-    items = by_negated_author(items)
     items = by_negated_assignee(items)
     items = by_negated_label(items)
     items = by_negated_milestone(items)
@@ -372,31 +373,13 @@ class IssuableFinder
   end
   # rubocop: enable CodeReuse/ActiveRecord
 
-  # rubocop: disable CodeReuse/ActiveRecord
   def by_author(items)
-    if params.author
-      items.where(author_id: params.author.id)
-    elsif params.no_author?
-      items.where(author_id: nil)
-    elsif params.author_id? || params.author_username? # author not found
-      items.none
-    else
-      items
-    end
+    Issuables::AuthorFilter.new(
+      items,
+      params: original_params,
+      not_filters_enabled: not_filters_enabled?
+    ).filter
   end
-  # rubocop: enable CodeReuse/ActiveRecord
-
-  # rubocop: disable CodeReuse/ActiveRecord
-  def by_negated_author(items)
-    if not_params.author
-      items.where.not(author_id: not_params.author.id)
-    elsif not_params.author_id? || not_params.author_username? # author not found
-      items.none
-    else
-      items
-    end
-  end
-  # rubocop: enable CodeReuse/ActiveRecord
 
   def by_assignee(items)
     if params.filter_by_no_assignee?
@@ -514,4 +497,14 @@ class IssuableFinder
   def by_non_archived(items)
     params[:non_archived].present? ? items.non_archived : items
   end
+
+  def not_filters_enabled?
+    strong_memoize(:not_filters_enabled) do
+      Feature.enabled?(:not_issuable_queries, feature_flag_scope, default_enabled: :yaml)
+    end
+  end
+
+  def feature_flag_scope
+    params.group || params.project
+  end
 end

app/finders/issuable_finder/params.rb

@@ -27,19 +27,6 @@ class IssuableFinder
       params.present?
     end
 
-    def author_id?
-      params[:author_id].present? && params[:author_id] != NONE
-    end
-
-    def author_username?
-      params[:author_username].present? && params[:author_username] != NONE
-    end
-
-    def no_author?
-      # author_id takes precedence over author_username
-      params[:author_id] == NONE || params[:author_username] == NONE
-    end
-
     def filter_by_no_assignee?
       params[:assignee_id].to_s.downcase == FILTER_NONE
     end
@@ -169,20 +156,6 @@ class IssuableFinder
       end
     end
 
-    # rubocop: disable CodeReuse/ActiveRecord
-    def author
-      strong_memoize(:author) do
-        if author_id?
-          User.find_by(id: params[:author_id])
-        elsif author_username?
-          User.find_by_username(params[:author_username])
-        else
-          nil
-        end
-      end
-    end
-    # rubocop: enable CodeReuse/ActiveRecord
-
     # rubocop: disable CodeReuse/ActiveRecord
     def assignees
       strong_memoize(:assignees) do

app/finders/issuables/author_filter.rb

+module Issuables
+  class AuthorFilter < BaseFilter
+    def filter
+      filtered = by_author(issuables)
+      by_negated_author(filtered)
+    end
+
+    private
+
+    def by_author(issuables)
+      if no_author?
+        issuables.where(author_id: nil)
+      elsif params[:author_id].present?
+        issuables.where(author_id: params[:author_id])
+      elsif params[:author_username].present?
+        issuables.where(author_id: authors_by_username(params[:author_username]))
+      else
+        issuables
+      end
+    end
+
+    def by_negated_author(issuables)
+      return issuables unless not_params.present? && not_filters_enabled?
+
+      if not_params[:author_id].present?
+        issuables.where.not(author_id: not_params[:author_id])
+      elsif not_params[:author_username].present?
+        issuables.where.not(author_id: authors_by_username(not_params[:author_username]))
+      else
+        issuables
+      end
+    end
+
+    def no_author?
+      # author_id takes precedence over author_username
+      params[:author_id] == NONE || params[:author_username] == NONE
+    end
+
+    def authors_by_username(usernames)
+      User.where(username: usernames)
+    end
+  end
+end

app/finders/issuables/base_filter.rb

+module Issuables
+  class BaseFilter
+    # This is used as a common filter for None / Any
+    FILTER_NONE = 'none'
+    FILTER_ANY = 'any'
+
+    # This is used in unassigning users
+    NONE = '0'
+
+    attr_reader :issuables, :params
+
+    def initialize(issuables, params:, not_filters_enabled: false)
+      @issuables = issuables
+      @params = params
+      @not_filters_enabled = not_filters_enabled
+    end
+
+    def filter
+      raise NotImplementedError
+    end
+
+    private
+
+    def not_params
+      params[:not]
+    end
+
+    def not_filters_enabled?
+      @not_filters_enabled
+    end
+  end
+end

ee/app/finders/epics_finder.rb

@@ -25,6 +25,7 @@
 class EpicsFinder < IssuableFinder
   include TimeFrameFilter
   include Gitlab::Utils::StrongMemoize
+  extend ::Gitlab::Utils::Override
 
   IID_STARTS_WITH_PATTERN = %r{\A(\d)+\z}.freeze
 
@@ -123,13 +124,12 @@ class EpicsFinder < IssuableFinder
   end
 
   def filter_negated_items(items)
-    return items unless Feature.enabled?(:not_issuable_queries, group, default_enabled: true)
+    return items unless not_filters_enabled?
 
     # API endpoints send in `nil` values so we test if there are any non-nil
     return items unless not_params&.values&.any?
 
-    items = by_negated_label(items)
-    by_negated_author(items)
+    by_negated_label(items)
   end
 
   def group
@@ -242,4 +242,9 @@ class EpicsFinder < IssuableFinder
   def group_projects
     Project.in_namespace(permissioned_related_groups).with_issues_available_for_user(current_user)
   end
+
+  override :feature_flag_scope
+  def feature_flag_scope
+    group
+  end
 end