Fix `JoinDependency` with using a custom table

Without this fix, `JoinDependency` doesn't use a custom table alias:

```
% ARCONN=sqlite3 be ruby -w -Itest test/cases/relations_test.rb -n test_using_a_custom_table_with_joins_affects_the_wheres
Using sqlite3
Run options: -n test_using_a_custom_table_with_joins_affects_the_wheres --seed 14531

E

Error:RelationTest#test_using_a_custom_table_with_joins_affects_the_wheres:
ActiveRecord::StatementInvalid: SQLite3::SQLException: no such column: posts.author_id: SELECT  "omg_posts".* FROM "posts" "omg_posts" INNER JOIN "authors" ON "authors"."id" = "posts"."author_id" WHERE "omg_posts"."title" = ? LIMIT ?
```

6 files changed, 29 insertions, 18 deletions

diff --git a/activerecord/lib/active_record/associations/join_dependency.rb b/activerecord/lib/active_record/associations/join_dependency.rb
index 5c8ecf42b4..4a3fb6eaec 100644
--- a/activerecord/lib/active_record/associations/join_dependency.rb
+++ b/activerecord/lib/active_record/associations/join_dependency.rb
@@ -88,11 +88,11 @@ module ActiveRecord
       #    associations # => [:appointments]
       #    joins # =>  []
       #
-      def initialize(base, associations, joins, eager_loading: true)
+      def initialize(base, table, associations, joins, eager_loading: true)
         @alias_tracker = AliasTracker.create_with_joins(base.connection, base.table_name, joins)
         @eager_loading = eager_loading
         tree = self.class.make_tree associations
-        @join_root = JoinBase.new base, build(tree, base)
+        @join_root = JoinBase.new(base, table, build(tree, base))
         @join_root.children.each { |child| construct_tables! @join_root, child }
       end
 
diff --git a/activerecord/lib/active_record/associations/join_dependency/join_base.rb b/activerecord/lib/active_record/associations/join_dependency/join_base.rb
index f5f22ebfca..d4e26d5397 100644
--- a/activerecord/lib/active_record/associations/join_dependency/join_base.rb
+++ b/activerecord/lib/active_record/associations/join_dependency/join_base.rb
@@ -4,14 +4,17 @@ module ActiveRecord
   module Associations
     class JoinDependency # :nodoc:
       class JoinBase < JoinPart # :nodoc:
+        attr_reader :table
+
+        def initialize(base_klass, table, children)
+          super(base_klass, children)
+          @table = table
+        end
+
         def match?(other)
           return true if self == other
           super && base_klass == other.base_klass
         end
-
-        def table
-          base_klass.arel_table
-        end
       end
     end
   end
diff --git a/activerecord/lib/active_record/relation/finder_methods.rb b/activerecord/lib/active_record/relation/finder_methods.rb
index 7121dcade8..57b7d3c2e9 100644
--- a/activerecord/lib/active_record/relation/finder_methods.rb
+++ b/activerecord/lib/active_record/relation/finder_methods.rb
@@ -397,7 +397,7 @@ module ActiveRecord
 
       def construct_join_dependency(joins = [], eager_loading: true)
         including = eager_load_values + includes_values
-        ActiveRecord::Associations::JoinDependency.new(@klass, including, joins, eager_loading: eager_loading)
+        ActiveRecord::Associations::JoinDependency.new(klass, table, including, joins, eager_loading: eager_loading)
       end
 
       def construct_relation_for_association_calculations
diff --git a/activerecord/lib/active_record/relation/merger.rb b/activerecord/lib/active_record/relation/merger.rb
index 5dac00724a..6251f6fc33 100644
--- a/activerecord/lib/active_record/relation/merger.rb
+++ b/activerecord/lib/active_record/relation/merger.rb
@@ -119,9 +119,10 @@ module ActiveRecord
               end
             end
 
-            join_dependency = ActiveRecord::Associations::JoinDependency.new(other.klass,
-                                                                             joins_dependency,
-                                                                             [])
+            join_dependency = ActiveRecord::Associations::JoinDependency.new(
+              other.klass, other.table, joins_dependency, []
+            )
+
             relation.joins! rest
 
             @relation = relation.joins join_dependency
diff --git a/activerecord/lib/active_record/relation/query_methods.rb b/activerecord/lib/active_record/relation/query_methods.rb
index c26c176c7b..efb55391e7 100644
--- a/activerecord/lib/active_record/relation/query_methods.rb
+++ b/activerecord/lib/active_record/relation/query_methods.rb
@@ -1020,9 +1020,7 @@ module ActiveRecord
         join_list = join_nodes + convert_join_strings_to_ast(manager, string_joins)
 
         join_dependency = ActiveRecord::Associations::JoinDependency.new(
-          @klass,
-          association_joins,
-          join_list
+          klass, table, association_joins, join_list
         )
 
         join_infos = join_dependency.join_constraints stashed_association_joins, join_type
diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index 82e1077e87..316ea75e36 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -1785,15 +1785,15 @@ class RelationTest < ActiveRecord::TestCase
   end
 
   test "using a custom table affects the wheres" do
-    table_alias = Post.arel_table.alias("omg_posts")
+    post = posts(:welcome)
 
-    table_metadata = ActiveRecord::TableMetadata.new(Post, table_alias)
-    predicate_builder = ActiveRecord::PredicateBuilder.new(table_metadata)
-    relation = ActiveRecord::Relation.create(Post, table_alias, predicate_builder)
+    assert_equal post, custom_post_relation.where!(title: post.title).take
+  end
 
+  test "using a custom table with joins affects the joins" do
     post = posts(:welcome)
 
-    assert_equal post, relation.where!(title: post.title).take
+    assert_equal post, custom_post_relation.joins(:author).where!(title: post.title).take
   end
 
   test "#load" do
@@ -1950,4 +1950,13 @@ class RelationTest < ActiveRecord::TestCase
       end
     end
   end
+
+  private
+    def custom_post_relation
+      table_alias = Post.arel_table.alias("omg_posts")
+      table_metadata = ActiveRecord::TableMetadata.new(Post, table_alias)
+      predicate_builder = ActiveRecord::PredicateBuilder.new(table_metadata)
+
+      ActiveRecord::Relation.create(Post, table_alias, predicate_builder)
+    end
 end