From 22162cccd5388f15de1098596dfa35cfeab2ca1e Mon Sep 17 00:00:00 2001
From: Gleb Mazovetskiy <glex.spb@gmail.com>
Date: Thu, 25 Jul 2019 19:42:07 +0100
Subject: [PATCH] Rails 6.2.0.rc2 compatibility

Rails 6.2.0.rc2 changed join order when combining Arel and Rails joins.
Worked around by using only Arel joins in the affected query.
See https://github.com/rails/rails/issues/36761

Fixes #822
---
 Gemfile                             |  2 +-
 app/models/thredded/messageboard.rb | 18 ++++++++++--------
 lib/thredded/db_tools.rb            | 11 ++++++-----
 spec/gemfiles/rails_6_0.gemfile     |  2 +-
 4 files changed, 18 insertions(+), 15 deletions(-)

diff --git a/Gemfile b/Gemfile
index f2dc8c65b..066446c58 100644
--- a/Gemfile
+++ b/Gemfile
@@ -2,7 +2,7 @@
 
 source 'https://rubygems.org'
 
-gem 'rails', '~> 6.0.0.rc1'
+gem 'rails', '~> 6.0.0.rc2'
 gem 'rails-i18n', '~> 6.0.0.beta1'
 
 # https://github.com/rails/rails/blob/v6.0.0.rc1/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb#L12
diff --git a/app/models/thredded/messageboard.rb b/app/models/thredded/messageboard.rb
index d9c307b4f..607ff8c3e 100644
--- a/app/models/thredded/messageboard.rb
+++ b/app/models/thredded/messageboard.rb
@@ -128,14 +128,16 @@ def unread_topics_counts(user:, topics_scope: Thredded::Topic.all)
         messageboards = arel_table
         read_states = Thredded::UserTopicReadState.arel_table
         topics = topics_scope.arel_table
-        joins(:topics).merge(topics_scope).joins(
-          messageboards.outer_join(read_states).on(
-            messageboards[:id].eq(read_states[:messageboard_id])
-              .and(read_states[:postable_id].eq(topics[:id]))
-              .and(read_states[:user_id].eq(user.id))
-              .and(read_states[:unread_posts_count].eq(0))
-          ).join_sources
-        ).group(messageboards[:id]).pluck(
+        joins(
+          messageboards.join(topics)
+            .on(topics[:messageboard_id].eq(messageboards[:id]))
+            .outer_join(read_states).on(
+              messageboards[:id].eq(read_states[:messageboard_id])
+                .and(read_states[:postable_id].eq(topics[:id]))
+                .and(read_states[:user_id].eq(user.id))
+                .and(read_states[:unread_posts_count].eq(0))
+            ).join_sources
+        ).merge(topics_scope).group(messageboards[:id]).pluck(
           :id,
           Arel::Nodes::Subtraction.new(topics[:id].count, read_states[:id].count)
         ).to_h
diff --git a/lib/thredded/db_tools.rb b/lib/thredded/db_tools.rb
index 74f814cb4..4f6d4866c 100644
--- a/lib/thredded/db_tools.rb
+++ b/lib/thredded/db_tools.rb
@@ -9,13 +9,14 @@ class << self
       def migrate(paths:, quiet:, &filter)
         verbose_was = ActiveRecord::Migration.verbose
         ActiveRecord::Migration.verbose = !quiet
-        migrate = -> {
-          if Rails::VERSION::STRING >= '5.2'
-            ActiveRecord::MigrationContext.new(paths).migrate(nil, &filter)
+        migrate =
+          if Rails.gem_version >= Gem::Version.new('6.0.0.rc2')
+            -> { ActiveRecord::MigrationContext.new(paths, ActiveRecord::SchemaMigration).migrate(nil, &filter) }
+          elsif Rails::VERSION::STRING >= '5.2'
+            -> {ActiveRecord::MigrationContext.new(paths).migrate(nil, &filter) }
           else
-            ActiveRecord::Migrator.migrate(paths, &filter)
+            -> { ActiveRecord::Migrator.migrate(paths, &filter) }
           end
-        }
         if quiet
           silence_active_record(&migrate)
         else
diff --git a/spec/gemfiles/rails_6_0.gemfile b/spec/gemfiles/rails_6_0.gemfile
index 0c2c1369f..5ce064c5f 100644
--- a/spec/gemfiles/rails_6_0.gemfile
+++ b/spec/gemfiles/rails_6_0.gemfile
@@ -4,7 +4,7 @@ source 'https://rubygems.org'
 gemspec path: '../../'
 eval_gemfile '../../shared.gemfile'
 
-gem 'rails', '~> 6.0.0.rc1'
+gem 'rails', '~> 6.0.0.rc2'
 gem 'rails-i18n', '~> 6.0.0.beta1'
 
 # https://github.com/rails/rails/blob/v6.0.0.rc1/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb#L12