From 7435f2e5165bf7864bc84cfb94adef02bb739006 Mon Sep 17 00:00:00 2001
From: evazion <noizave@gmail.com>
Date: Tue, 1 Feb 2022 00:59:42 -0600
Subject: [PATCH] Fix #4969: Tag changes made by replacements wipe out edits
 done at the same time.

Lock the post during replacement to ensure we have the latest version of
the tags and to ensure nobody else can modify the post until after the
replacement is finished.
---
 app/logical/post_replacement_processor.rb            | 3 ++-
 app/models/post_replacement.rb                       | 2 --
 test/functional/post_replacements_controller_test.rb | 5 ++++-
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/app/logical/post_replacement_processor.rb b/app/logical/post_replacement_processor.rb
index 14b0590c6..01f4cdfa2 100644
--- a/app/logical/post_replacement_processor.rb
+++ b/app/logical/post_replacement_processor.rb
@@ -34,13 +34,14 @@ class PostReplacementProcessor
     replacement.image_width = media_asset.image_width
     replacement.md5 = media_asset.md5
 
+    post.lock!
     post.md5 = media_asset.md5
     post.file_ext = media_asset.file_ext
     post.image_width = media_asset.image_width
     post.image_height = media_asset.image_height
     post.file_size = media_asset.file_size
     post.source = replacement.final_source.presence || replacement.replacement_url
-    post.tag_string = replacement.tags
+    post.tag_string = "#{post.tag_string} #{replacement.tags}"
 
     rescale_notes(post)
     post.save!
diff --git a/app/models/post_replacement.rb b/app/models/post_replacement.rb
index 099a9c4fd..bbebbfffe 100644
--- a/app/models/post_replacement.rb
+++ b/app/models/post_replacement.rb
@@ -12,8 +12,6 @@ class PostReplacement < ApplicationRecord
 
   def initialize_fields
     self.original_url = post.source
-    self.tags = "#{post.tag_string} #{tags}"
-
     self.old_file_ext = post.file_ext
     self.old_file_size = post.file_size
     self.old_image_width = post.image_width
diff --git a/test/functional/post_replacements_controller_test.rb b/test/functional/post_replacements_controller_test.rb
index 9380dfd6e..abfddbca8 100644
--- a/test/functional/post_replacements_controller_test.rb
+++ b/test/functional/post_replacements_controller_test.rb
@@ -6,13 +6,14 @@ class PostReplacementsControllerTest < ActionDispatch::IntegrationTest
       context "replacing a post from a source url" do
         should "replace the post" do
           assert_difference("PostReplacement.count") do
-            @post = create(:post)
+            @post = create(:post, tag_string: "image_sample")
 
             post_auth post_replacements_path, create(:moderator_user), params: {
               format: :json,
               post_id: @post.id,
               post_replacement: {
                 replacement_url: "https://cdn.donmai.us/original/d3/4e/d34e4cf0a437a5d65f8e82b7bcd02606.jpg",
+                tags: "replaced -image_sample"
               }
             }
 
@@ -31,6 +32,7 @@ class PostReplacementsControllerTest < ActionDispatch::IntegrationTest
           assert_equal(@post.file_size, @replacement.old_file_size)
           assert_equal(@post.file_ext, @replacement.old_file_ext)
           assert_equal(@post.md5, @replacement.old_md5)
+          assert_equal(@post.tag_string, "image_sample")
 
           @post.reload
           assert_equal("d34e4cf0a437a5d65f8e82b7bcd02606", @post.md5)
@@ -40,6 +42,7 @@ class PostReplacementsControllerTest < ActionDispatch::IntegrationTest
           assert_equal(650, @post.image_height)
           assert_equal(127_238, @post.file_size)
           assert_equal("jpg", @post.file_ext)
+          assert_equal("replaced", @post.tag_string)
         end
       end