Respect new records for CollectionProxy#uniq

[kamipo]

Currently if CollectionProxy has more than one new record,
CollectionProxy#uniq result is incorrect.

And CollectionProxy#uniq was aliased to distinct in a1bb6c8.
But the uniq method and the SELECT DISTINCT method are different
methods. The doc in CollectionProxy is for the SELECT DISTINCT
method, not for the uniq method.

Therefore, reverting the alias in CollectionProxy to fix the
inconsistency and to have the both methods.

[rails-bot]

r? @sgrif

(@rails-bot has picked a reviewer for you, use r? to override)

[sgrif]

I would have expected this code to just do SELECT DISTINCT and not do it in memory.

[kamipo]

This method exists since the initial commit.

rails/activerecord/lib/active_record/associations/association_collection.rb

Lines 72 to 74 in db045db

	def uniq(collection = self)
	collection.inject([]) { |uniq_records, record| uniq_records << record unless uniq_records.include?(record); uniq_records }
	end

SELECT DISTINCT method was added since v3.2.0.rc1.
562583c#diff-bf6dd6226db3aab589916f09236881c7R190

If we expects SELECT DISTINCT, should we remove the method? (CollectionProxy already have SELECT DISTINCT method because inherits Relation but overridden by the method)

[seanlinsley]

It would be useful to backport this to 5.0.x. Here's my failing test and the git bisect setup I used to discover this commit fixed it:

# Note that "good" and "bad" are reversed, because `git bisect` is only built to work in one direction.
# I use the trick shown here: http://stackoverflow.com/a/36157747/2651774 to get around that.

# git bisect start
# git bisect bad master
# git bisect good 5-0-stable^
# git bisect skip
# git bisect run bash -c "! ruby test.rb"

# fixed commit: 0ec967aa6655d62c92f72acb8d556a5b3f70762d

begin
  require "bundler/inline"
rescue LoadError => e
  $stderr.puts "Bundler version 1.10 or later is required. Please update your Bundler"
  raise e
end

gemfile(true) do
  source "https://rubygems.org"
  gem "rails", path: "."
  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|
  end

  create_table :comments, force: true do |t|
    t.integer :post_id
    t.string :comment
  end
end

class Post < ActiveRecord::Base
  has_many :comments
end

class Comment < ActiveRecord::Base
  belongs_to :post
end

class BugTest < Minitest::Test
  def test_association_stuff
    post = Post.create!
    post.comments << Comment.create!(comment: 'test')
    post.comments << Comment.create!(comment: 'test')

    assert_equal ['test', 'test'], Post.last.comments.pluck(:comment)
    assert_equal ['test'], Post.last.comments.distinct.pluck(:comment)
  end
end