Add fix for migration #587

db/migrate/20240215100000_fix_unread_comments_inconsistencies_again.rb

@@ -0,0 +1,45 @@
+# Fixes the unread_comments flag for all users. Unintended behavior was
+# introduced in pull request #515. Behavior fixed in #585
+# A migration was introduced in #587, but it turned out it contained a bug.
+# This migration here is a fix for the migration in #587.
+#
+# This migration is generally *not* idempotent since users might have interacted
+# with the website since the migration was run and thus they will probably have
+# different unread comments flags as the ones at the time of the migration.
+#
+# This migration is not reversible as we don't store the previous state of
+# the unread_comments flag.
+class FixUnreadCommentsInconsistenciesAgain < ActiveRecord::Migration[7.0]
+  def up
+    num_fixed_users = 0
+
+    User.find_each do |user|
+      had_user_unread_comments = user.unread_comments # boolean
+      has_user_unread_comments = user_unread_comments?(user)
+
+      has_flag_changed = (had_user_unread_comments != has_user_unread_comments)
+      user.update(unread_comments: has_user_unread_comments) if has_flag_changed
+      num_fixed_users += 1 if has_flag_changed
+    end
+
+    Rails.logger.warn { "Ran through #{User.count} users (unread comments flag again)" }
+    Rails.logger.warn { "Fixed #{num_fixed_users} users (unread comments flag again)" }
+  end
+
+  # Checks and returns whether the user has unread comments.
+  def user_unread_comments?(user)
+    # see the method "comments" in app/controllers/main_controller.rb
+    unseen_media = user.subscribed_media_with_latest_comments_not_by_creator
+    unseen_media.select! do |m|
+      (Reader.find_by(user: user, thread: m[:thread])
+            &.updated_at || 1000.years.ago) < m[:latest_comment].created_at &&
+        m[:medium].visible_for_user?(user)
+    end
+
+    unseen_media.present?
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.0].define(version: 2024_01_16_180000) do
+ActiveRecord::Schema[7.0].define(version: 2024_02_15_100000) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pgcrypto"
   enable_extension "plpgsql"