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rails--rails/activerecord/test/cases/test_case.rb
Daniel Colson 518b9a301f
Automatically infer inverse_of with scopes
Background
---

I recently noticed we had a number of associations in GitHub that would
benefit from having `inverse_of` set, and so I began adding them. I
ended up adding them to virtually every association with a scope, at
which point I wondered whether Rails might be able to automatically find
these inverses for us.

For GitHub, the changes in this commit end up automatically adding
`inverse_of` to 171 of associations that were missing it.

My understanding is that we do not automatically detect `inverse_of` for
associations with scopes because the scopes could exclude the records we
are trying to inverse from. But I think that should only matter if there
is a scope on the inverse side, not on the association itself.

For example:

Scope on has_many
----

```rb
class Post < ActiveRecord::Base
  has_many :comments, -> { visible }
end

class Comment < ActiveRecord::Base
  belongs_to :post

  scope :visible, -> { where(visible: true) }
  scope :hidden, -> { where(visible: false) }
end

post = Post.create!
comment = post.comments.hidden.create!
assert comment.post
```

This code leaves `post.comments` in sort of a weird state, since it
includes a comment that the association would filter out. But that's
true regardless of the changes in this commit.

Regardless of whether the comments association has an inverse,
`comment.post` will return the post. The difference is that when
`inverse_of` is set we use the existing post we have in memory, rather
than loading it again. If there is a downside to having the `inverse_of`
automatically set here I'm not seeing it.

Scope on belongs_to
----

```rb
class Post < ActiveRecord::Base
  has_many :comments

  scope :visible, -> { where(visible: true) }
  scope :hidden, -> { where(visible: false) }
end

class Comment < ActiveRecord::Base
  belongs_to :post, -> { visible }
end

post = Post.hidden.create!
comment = post.comments.create!
assert_nil comment.post
```

This example is a different story. We don't want to automatically infer
the inverse here because that would change the behavior of
`comment.post`. It should return `nil`, since it's scoped to visible
posts while this one is hidden.

This behavior was not well tested, so this commit adds a test to
ensure we haven't changed it.

Changes
---

This commit changes `can_find_inverse_of_automatically` to allow us to
automatically detect `inverse_of` when there is a scope on the
association, but not when there is a scope on the potential inverse
association. (`can_find_inverse_of_automatically` gets called first with
the association's reflection, then if it returns true we attempt to find
the inverse reflection, and finally we call the method again with the
inverse reflection to ensure we can really use it.)

Since this is a breaking change—specifically in places where code may
have relied on a missing `inverse_of` causing fresh copies of a record
to be loaded—we've placed it behind the `automatic_scope_inversing` flag
(whose name was inspired by `has_many_inversing`). It is set to true for
new applications via framework defaults.

Testing
---

In addition to the inverse association tests, this commit also adds some
cases to a few tests related to preloading. They are basically
duplicates of existing tests, but with lower query counts.

Testing this change with GitHub, the bulk of the failing tests were
related to lower query counts. There were additionally 3 places (2 in
tests and one in application code) where we relied on missing
`inverse_of` causing fresh copies of a record to be loaded.

There's still one Rails test that wouldn't pass if we ran the whole
suite with `automatic_scope_inversing = true`. It's related to
`TaggedPost`, which changes the polymorphic type from the base class
`Post` to the subclass `TaggedPost`.

```rb
class TaggedPost < Post
  has_many :taggings, -> { rewhere(taggable_type: "TaggedPost") }, as: :taggable
end
```

Setting the inverse doesn't work because it ends up changing the type
back to `Post`, something like this:

```rb
post = TaggedPost.new
tagging = post.taggings.new
puts tagging.taggable_type
=> TaggedPost

tagging.taggable = post
puts tagging.taggable_type
=> Post
```

I think this is an acceptable change, given that it's a fairly specific
scenario, and is sort of at odds with the way polymorphic associations
are meant to work (they are meant to contain the base class, not the
subclass). If someone is relying on this specific behavior they can
still either keep `automatic_scope_inversing` set to false, or they can
add `inverse_of: false` to the association.

I haven't found any other cases where having the `inverse_of` would
cause problems like this.

Co-authored-by: Chris Bloom <chrisbloom7@gmail.com>
2021-10-04 09:42:04 -04:00

175 lines
5.8 KiB
Ruby

# frozen_string_literal: true
require "active_support"
require "active_support/testing/autorun"
require "active_support/testing/method_call_assertions"
require "active_support/testing/stream"
require "active_record/fixtures"
require "cases/validations_repair_helper"
module ActiveRecord
# = Active Record Test Case
#
# Defines some test assertions to test against SQL queries.
class TestCase < ActiveSupport::TestCase # :nodoc:
include ActiveSupport::Testing::MethodCallAssertions
include ActiveSupport::Testing::Stream
include ActiveRecord::TestFixtures
include ActiveRecord::ValidationsRepairHelper
self.fixture_path = FIXTURES_ROOT
self.use_instantiated_fixtures = false
self.use_transactional_tests = true
def create_fixtures(*fixture_set_names, &block)
ActiveRecord::FixtureSet.create_fixtures(ActiveRecord::TestCase.fixture_path, fixture_set_names, fixture_class_names, &block)
end
def teardown
SQLCounter.clear_log
end
def capture_sql
ActiveRecord::Base.connection.materialize_transactions
SQLCounter.clear_log
yield
SQLCounter.log.dup
end
def assert_sql(*patterns_to_match, &block)
capture_sql(&block)
ensure
failed_patterns = []
patterns_to_match.each do |pattern|
failed_patterns << pattern unless SQLCounter.log_all.any? { |sql| pattern === sql }
end
assert failed_patterns.empty?, "Query pattern(s) #{failed_patterns.map(&:inspect).join(', ')} not found.#{SQLCounter.log.size == 0 ? '' : "\nQueries:\n#{SQLCounter.log.join("\n")}"}"
end
def assert_queries(num = 1, options = {})
ignore_none = options.fetch(:ignore_none) { num == :any }
ActiveRecord::Base.connection.materialize_transactions
SQLCounter.clear_log
x = yield
the_log = ignore_none ? SQLCounter.log_all : SQLCounter.log
if num == :any
assert_operator the_log.size, :>=, 1, "1 or more queries expected, but none were executed."
else
mesg = "#{the_log.size} instead of #{num} queries were executed.#{the_log.size == 0 ? '' : "\nQueries:\n#{the_log.join("\n")}"}"
assert_equal num, the_log.size, mesg
end
x
end
def assert_no_queries(options = {}, &block)
options.reverse_merge! ignore_none: true
assert_queries(0, options, &block)
end
def assert_column(model, column_name, msg = nil)
assert has_column?(model, column_name), msg
end
def assert_no_column(model, column_name, msg = nil)
assert_not has_column?(model, column_name), msg
end
def has_column?(model, column_name)
model.reset_column_information
model.column_names.include?(column_name.to_s)
end
def with_has_many_inversing(model = ActiveRecord::Base)
old = model.has_many_inversing
model.has_many_inversing = true
yield
ensure
model.has_many_inversing = old
if model != ActiveRecord::Base && !old
model.singleton_class.remove_method(:has_many_inversing) # reset the class_attribute
end
end
def with_automatic_scope_inversing(*reflections)
old = reflections.map { |reflection| reflection.klass.automatic_scope_inversing }
reflections.each do |reflection|
reflection.klass.automatic_scope_inversing = true
reflection.remove_instance_variable(:@inverse_name) if reflection.instance_variable_defined?(:@inverse_name)
reflection.remove_instance_variable(:@inverse_of) if reflection.instance_variable_defined?(:@inverse_of)
end
yield
ensure
reflections.each_with_index do |reflection, i|
reflection.klass.automatic_scope_inversing = old[i]
reflection.remove_instance_variable(:@inverse_name) if reflection.instance_variable_defined?(:@inverse_name)
reflection.remove_instance_variable(:@inverse_of) if reflection.instance_variable_defined?(:@inverse_of)
end
end
def reset_callbacks(klass, kind)
old_callbacks = {}
old_callbacks[klass] = klass.send("_#{kind}_callbacks").dup
klass.subclasses.each do |subclass|
old_callbacks[subclass] = subclass.send("_#{kind}_callbacks").dup
end
yield
ensure
klass.send("_#{kind}_callbacks=", old_callbacks[klass])
klass.subclasses.each do |subclass|
subclass.send("_#{kind}_callbacks=", old_callbacks[subclass])
end
end
def with_postgresql_datetime_type(type)
adapter = ActiveRecord::ConnectionAdapters::PostgreSQLAdapter
adapter.remove_instance_variable(:@native_database_types) if adapter.instance_variable_defined?(:@native_database_types)
datetime_type_was = adapter.datetime_type
adapter.datetime_type = type
yield
ensure
adapter = ActiveRecord::ConnectionAdapters::PostgreSQLAdapter
adapter.datetime_type = datetime_type_was
adapter.remove_instance_variable(:@native_database_types) if adapter.instance_variable_defined?(:@native_database_types)
end
end
class PostgreSQLTestCase < TestCase
def self.run(*args)
super if current_adapter?(:PostgreSQLAdapter)
end
end
class Mysql2TestCase < TestCase
def self.run(*args)
super if current_adapter?(:Mysql2Adapter)
end
end
class SQLite3TestCase < TestCase
def self.run(*args)
super if current_adapter?(:SQLite3Adapter)
end
end
class SQLCounter
class << self
attr_accessor :ignored_sql, :log, :log_all
def clear_log; self.log = []; self.log_all = []; end
end
clear_log
def call(name, start, finish, message_id, values)
return if values[:cached]
sql = values[:sql]
self.class.log_all << sql
self.class.log << sql unless ["SCHEMA", "TRANSACTION"].include? values[:name]
end
end
ActiveSupport::Notifications.subscribe("sql.active_record", SQLCounter.new)
end