Arel: add the possibility to instantiate directly a TreeManager with …

…an ast

activerecord/lib/arel/delete_manager.rb

@@ -5,7 +5,7 @@ class DeleteManager < Arel::TreeManager
     include TreeManager::StatementMethods
 
     def initialize(table = nil)
-      @ast = Nodes::DeleteStatement.new(table)
+      super(Nodes::DeleteStatement.new(table))
     end
 
     def from(relation)

activerecord/lib/arel/insert_manager.rb

@@ -3,7 +3,7 @@
 module Arel # :nodoc: all
   class InsertManager < Arel::TreeManager
     def initialize(table = nil)
-      @ast = Nodes::InsertStatement.new(table)
+      super(Nodes::InsertStatement.new(table))
     end
 
     def into(table)

activerecord/lib/arel/select_manager.rb

@@ -7,8 +7,8 @@ class SelectManager < Arel::TreeManager
     STRING_OR_SYMBOL_CLASS = [Symbol, String]
 
     def initialize(table = nil)
-      @ast = Nodes::SelectStatement.new(table)
-      @ctx = @ast.cores.last
+      super(Nodes::SelectStatement.new(table))
+      @ctx = ast.cores.last
     end
 
     def initialize_copy(other)

activerecord/lib/arel/tree_manager.rb

@@ -40,6 +40,14 @@ def where(expr)
 
     attr_reader :ast
 
+    def initialize(ast)
+      @ast = ast
+    end
+
+    def initialize_copy(other)
+      super(other.clone)
+    end
+
     def to_dot
       collector = Arel::Collectors::PlainString.new
       collector = Visitors::Dot.new.accept @ast, collector
@@ -51,10 +59,5 @@ def to_sql(engine = Table.engine)
       collector = engine.connection.visitor.accept @ast, collector
       collector.value
     end
-
-    def initialize_copy(other)
-      super
-      @ast = @ast.clone
-    end
   end
 end

activerecord/lib/arel/update_manager.rb

@@ -5,7 +5,7 @@ class UpdateManager < Arel::TreeManager
     include TreeManager::StatementMethods
 
     def initialize(table = nil)
-      @ast = Nodes::UpdateStatement.new(table)
+      super(Nodes::UpdateStatement.new(table))
     end
 
     ###

activerecord/test/cases/arel/tree_manager_test.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+require_relative "helper"
+
+module Arel
+  class TreeManagerTest < Arel::Spec
+    describe "to_sql" do
+      it "generates SQL" do
+        users_table = Table.new(:users)
+        tree_manager = Arel::TreeManager.new(users_table[:first_name])
+        assert_equal('"users"."first_name"', tree_manager.to_sql)
+      end
+    end
+  end
+end