Backport CE changes from draft_notes addition in EE

app/models/concerns/diff_positionable_note.rb

+# frozen_string_literal: true
+module DiffPositionableNote
+  extend ActiveSupport::Concern
+
+  included do
+    before_validation :set_original_position, on: :create
+    before_validation :update_position, on: :create, if: :on_text?
+
+    serialize :original_position, Gitlab::Diff::Position # rubocop:disable Cop/ActiveRecordSerialize
+    serialize :position, Gitlab::Diff::Position # rubocop:disable Cop/ActiveRecordSerialize
+    serialize :change_position, Gitlab::Diff::Position # rubocop:disable Cop/ActiveRecordSerialize
+  end
+
+  %i(original_position position change_position).each do |meth|
+    define_method "#{meth}=" do |new_position|
+      if new_position.is_a?(String)
+        new_position = JSON.parse(new_position) rescue nil
+      end
+
+      if new_position.is_a?(Hash)
+        new_position = new_position.with_indifferent_access
+        new_position = Gitlab::Diff::Position.new(new_position)
+      end
+
+      return if new_position == read_attribute(meth)
+
+      super(new_position)
+    end
+  end
+
+  def on_text?
+    position&.position_type == "text"
+  end
+
+  def on_image?
+    position&.position_type == "image"
+  end
+
+  def supported?
+    for_commit? || self.noteable.has_complete_diff_refs?
+  end
+
+  def active?(diff_refs = nil)
+    return false unless supported?
+    return true if for_commit?
+
+    diff_refs ||= noteable.diff_refs
+
+    self.position.diff_refs == diff_refs
+  end
+
+  def set_original_position
+    return unless position
+
+    self.original_position = self.position.dup unless self.original_position&.complete?
+  end
+
+  def update_position
+    return unless supported?
+    return if for_commit?
+
+    return if active?
+    return unless position
+
+    tracer = Gitlab::Diff::PositionTracer.new(
+      project: self.project,
+      old_diff_refs: self.position.diff_refs,
+      new_diff_refs: self.noteable.diff_refs,
+      paths: self.position.paths
+    )
+
+    result = tracer.trace(self.position)
+    return unless result
+
+    if result[:outdated]
+      self.change_position = result[:position]
+    else
+      self.position = result[:position]
+    end
+  end
+end

app/models/diff_note.rb

@@ -5,14 +5,11 @@
 # A note of this type can be resolvable.
 class DiffNote < Note
   include NoteOnDiff
+  include DiffPositionableNote
   include Gitlab::Utils::StrongMemoize
 
   NOTEABLE_TYPES = %w(MergeRequest Commit).freeze
 
-  serialize :original_position, Gitlab::Diff::Position # rubocop:disable Cop/ActiveRecordSerialize
-  serialize :position, Gitlab::Diff::Position # rubocop:disable Cop/ActiveRecordSerialize
-  serialize :change_position, Gitlab::Diff::Position # rubocop:disable Cop/ActiveRecordSerialize
-
   validates :original_position, presence: true
   validates :position, presence: true
   validates :line_code, presence: true, line_code: true, if: :on_text?
@@ -21,8 +18,6 @@ class DiffNote < Note
   validate :verify_supported
   validate :diff_refs_match_commit, if: :for_commit?
 
-  before_validation :set_original_position, on: :create
-  before_validation :update_position, on: :create, if: :on_text?
   before_validation :set_line_code, if: :on_text?
   after_save :keep_around_commits
   after_commit :create_diff_file, on: :create
@@ -31,31 +26,6 @@ class DiffNote < Note
     DiffDiscussion
   end
 
-  %i(original_position position change_position).each do |meth|
-    define_method "#{meth}=" do |new_position|
-      if new_position.is_a?(String)
-        new_position = JSON.parse(new_position) rescue nil
-      end
-
-      if new_position.is_a?(Hash)
-        new_position = new_position.with_indifferent_access
-        new_position = Gitlab::Diff::Position.new(new_position)
-      end
-
-      return if new_position == read_attribute(meth)
-
-      super(new_position)
-    end
-  end
-
-  def on_text?
-    position.position_type == "text"
-  end
-
-  def on_image?
-    position.position_type == "image"
-  end
-
   def create_diff_file
     return unless should_create_diff_file?
 
@@ -87,15 +57,6 @@ class DiffNote < Note
     self.diff_file.line_code(self.diff_line)
   end
 
-  def active?(diff_refs = nil)
-    return false unless supported?
-    return true if for_commit?
-
-    diff_refs ||= noteable.diff_refs
-
-    self.position.diff_refs == diff_refs
-  end
-
   def created_at_diff?(diff_refs)
     return false unless supported?
     return true if for_commit?
@@ -141,37 +102,10 @@ class DiffNote < Note
     for_commit? || self.noteable.has_complete_diff_refs?
   end
 
-  def set_original_position
-    self.original_position = self.position.dup unless self.original_position&.complete?
-  end
-
   def set_line_code
     self.line_code = self.position.line_code(self.project.repository)
   end
 
-  def update_position
-    return unless supported?
-    return if for_commit?
-
-    return if active?
-
-    tracer = Gitlab::Diff::PositionTracer.new(
-      project: self.project,
-      old_diff_refs: self.position.diff_refs,
-      new_diff_refs: self.noteable.diff_refs,
-      paths: self.position.paths
-    )
-
-    result = tracer.trace(self.position)
-    return unless result
-
-    if result[:outdated]
-      self.change_position = result[:position]
-    else
-      self.position = result[:position]
-    end
-  end
-
   def verify_supported
     return if supported?