Arel table alias breaks insert, update, and delete statements

[lavoiesl]

Steps to reproduce

# frozen_string_literal: true

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"

  git_source(:github) { |repo| "https://github.com/#{repo}.git" }

  # Activate the gem you are reporting the issue against.
  gem "activerecord", "~> 7.0.0"
  gem "sqlite3"
end

require "active_record"
require "minitest/autorun"
require "logger"

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :posts, force: true do |t|
    t.string "name"
  end
end

class Post < ActiveRecord::Base
end


class BugTest < Minitest::Test
  def setup
    Post.arel_table.table_alias = nil
  end

  def test_select
    assert_equal('SELECT "posts".* FROM "posts"', Post.all.to_sql)
  end

  def test_select_alias
    Post.arel_table.table_alias = "p"
    assert_equal('SELECT "p".* FROM "posts" "p"', Post.all.to_sql)
  end

  def test_insert
    post = Post.create!
    refute_nil(post)
  end

  def test_insert_alias
    Post.arel_table.table_alias = "p"
    e = assert_raises(ActiveRecord::StatementInvalid) do
      Post.create!
    end
    assert_equal('INSERT INTO "posts" "p" DEFAULT VALUES', e.sql)
    assert_equal('SQLite3::SQLException: near ""p"": syntax error', e.message)
  end

  def test_update
    post = Post.create!
    refute_nil(post)
    post.name = "foo"
    post.save!
  end

  def test_update_alias
    post = Post.create!
    refute_nil(post)

    Post.arel_table.table_alias = "p"
    e = assert_raises(ActiveRecord::StatementInvalid) do
      post.name = "foo"
      post.save!
    end
    assert_equal('UPDATE "posts" "p" SET "name" = ? WHERE "p"."id" = ?', e.sql)
    assert_equal('SQLite3::SQLException: near ""p"": syntax error', e.message)
  end

  def test_delete
    post = Post.create!
    refute_nil(post)
    post.delete
  end

  def test_delete_alias
    post = Post.create!
    refute_nil(post)

    Post.arel_table.table_alias = "p"
    e = assert_raises(ActiveRecord::StatementInvalid) do
      post.delete
    end
    assert_equal('DELETE FROM "posts" "p" WHERE "p"."id" = ?', e.sql)
    assert_equal('SQLite3::SQLException: near ""p"": syntax error', e.message)
  end
end

Expected behavior

The table alias is valid on SELECTs, but not on INSERT, UPDATE, or DELETE statements.
The example is with sqlite, but MySQL has similar rules where it specifically asks for a table name.

I would expect Arel to NOT use the alias on insert, update, and delete statements

System configuration

Rails version:
6.1.7.4

Ruby version:
3.2.2

MySQL:
MySQL 5.7, using the mysql2 0.5.5 gem

[lavoiesl]

I locate the issue as being that ToSql#visit_Arel_Nodes_InsertStatement calls the visitor on the relation:

rails/activerecord/lib/arel/visitors/to_sql.rb

Lines 51 to 53 in 0ccde29

	def visit_Arel_Nodes_InsertStatement(o, collector)
	collector << "INSERT INTO "
	collector = visit o.relation, collector

which ends up calling:

rails/activerecord/lib/arel/visitors/to_sql.rb

Lines 577 to 579 in 0ccde29

	if o.table_alias
	collector << " " << quote_table_name(o.table_alias)
	end

Perhaps visit_Arel_Nodes_{Insert,Update,Delete}Statement should call quote_table_name(o.relation.name) directly?

[lavoiesl]

Yes, the tests are currently testing the failure. Would you prefer a version of the tests that properly fail?

[paulreece]

Thanks for clarifying! Nope, I now have your tests failing with my fix :)