Association using unscope: NoMethodError: undefined method `children' for nil:NilClass #38811

dvandersluis · 2020-03-24T21:23:10Z

Steps to reproduce

Have the following models:

class Post < ApplicationRecord
  has_many :tags, -> { unscope(:where) }
end

class Tag < ApplicationRecord
  default_scope { where(locale: :en) }
end

The following code will crash (even if the default_scope is removed):

Post.joins(:tags).to_sql

Expected behavior

Join tags to posts without the default scope being applied. Should generate a query something like:

SELECT "posts".* FROM "posts" INNER JOIN "tags" ON "tags"."post_id" = "posts"."id"

This was the behaviour in Rails 5.2.3.

Actual behavior

Exception: NoMethodError: undefined method `children' for nil:NilClass
--
 0: /Users/daniel/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/activerecord-6.0.2.2/lib/active_record/associations/join_dependency/join_association.rb:39:in `block in join_constraints'
 1: /Users/daniel/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/activerecord-6.0.2.2/lib/active_record/associations/join_dependency/join_association.rb:30:in `reverse_each'
 2: /Users/daniel/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/activerecord-6.0.2.2/lib/active_record/associations/join_dependency/join_association.rb:30:in `with_index'
 3: /Users/daniel/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/activerecord-6.0.2.2/lib/active_record/associations/join_dependency/join_association.rb:30:in `join_constraints'
 4: /Users/daniel/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/activerecord-6.0.2.2/lib/active_record/associations/join_dependency.rb:162:in `make_constraints'
 5: /Users/daniel/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/activerecord-6.0.2.2/lib/active_record/associations/join_dependency.rb:155:in `block in make_join_constraints'
 6: /Users/daniel/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/activerecord-6.0.2.2/lib/active_record/associations/join_dependency.rb:154:in `each'
 7: /Users/daniel/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/activerecord-6.0.2.2/lib/active_record/associations/join_dependency.rb:154:in `flat_map'
 8: /Users/daniel/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/activerecord-6.0.2.2/lib/active_record/associations/join_dependency.rb:154:in `make_join_constraints'
 9: /Users/daniel/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/activerecord-6.0.2.2/lib/active_record/associations/join_dependency.rb:85:in `join_constraints'
10: /Users/daniel/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/activerecord-6.0.2.2/lib/active_record/relation/query_methods.rb:1179:in `build_join_query'
11: /Users/daniel/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/activerecord-6.0.2.2/lib/active_record/relation/query_methods.rb:1164:in `build_joins'
12: /Users/daniel/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/activerecord-6.0.2.2/lib/active_record/relation/query_methods.rb:1044:in `build_arel'
13: /Users/daniel/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/activerecord-6.0.2.2/lib/active_record/relation/query_methods.rb:1016:in `arel'
14: /Users/daniel/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/activerecord-6.0.2.2/lib/active_record/relation.rb:810:in `block in exec_queries'
15: /Users/daniel/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/activerecord-6.0.2.2/lib/active_record/relation.rb:828:in `skip_query_cache_if_necessary'
16: /Users/daniel/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/activerecord-6.0.2.2/lib/active_record/relation.rb:797:in `exec_queries'
17: /Users/daniel/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/activerecord-6.0.2.2/lib/active_record/relation.rb:615:in `load'
18: /Users/daniel/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/activerecord-6.0.2.2/lib/active_record/relation.rb:250:in `records'
19: /Users/daniel/.rbenv/versions/2.6.2/lib/ruby/gems/2.6.0/gems/activerecord-6.0.2.2/lib/active_record/relation.rb:245:in `to_ary'

System configuration

Rails version:
Works in 5.2.3, broken in 5.2.4.2 and 6.0.2.2.

Ruby version:
2.6.2

The text was updated successfully, but these errors were encountered:

kamipo · 2020-03-24T21:34:21Z

Can you provide a reproduction script with this template https://github.com/rails/rails/blob/master/guides/bug_report_templates/active_record_master.rb?

dvandersluis · 2020-03-24T21:45:43Z

@kamipo Absolutely!

https://gist.github.com/dvandersluis/86eb48649747c763dd06fb1bc35a4321

imrubyist · 2020-04-01T13:02:49Z

@kamipo - Is this already fixed? Just run that test and I confirmed it works with ruby 2.6.3p62

Update: that test installed rails 6.1.0.alpha. Sorry. I'll try again.

More update: still unable to reproduce it with this updated test: https://gist.github.com/kevinhq/3c5f9d000d6f3ddc648ba87d35cffc89.

Ruby 2.6.3p62 and Rails 6.0.2.2

mechanicles · 2020-04-01T13:58:52Z

I also tested this issue but found that it does work perfectly with Ruby version 2.6.0 and Rails versions 5.2.4.2 and 6.0.2.2.

It also works fine with recent Ruby version and Rails version.

alboyadjian · 2020-04-01T17:38:22Z

I'm getting the same error after upgrading to 5.2.4.2. Created a reproduction gist based on @kevinhq 's
https://gist.github.com/alboyadjian/189e062cc814b57d8ab1a48e94486d36

dvandersluis · 2020-04-01T18:31:38Z

I tried to track this down and I think it relates to this line: https://github.com/rails/rails/blob/master/activerecord/lib/active_record/relation/query_methods.rb#L479

If unscope is just given a symbol (:where in this case) the entire key is deleted from @values, which seems to mean the join conditions are killed too. Previously (as of 5.2.3), it replaced them with the default values instead, which I think included join conditions.

A workaround I've found is to use the hash form unscope(where: :foo), which is a bit more brittle depending on how often your default scope is being changed but avoids the error.

alboyadjian · 2020-04-01T19:05:40Z

Thanks @dvandersluis. Changing to the hash form fixed the tests that were failing because of this. There don't seem to be any problems with unscope when used inside a scope, just when it's used in an association definition.

imrubyist · 2020-04-02T04:15:50Z

I'm getting the same error after upgrading to 5.2.4.2. Created a reproduction gist based on @kevinhq 's
https://gist.github.com/alboyadjian/189e062cc814b57d8ab1a48e94486d36

Confirmed this.

Error happened on 5.2.4.2 with ruby 2.6.2p47 (2019-03-13 revision 67232) [x86_64-darwin19]

Error:
BugTest#test_association_stuff:
NoMethodError: undefined method `children' for nil:NilClass

rails#29589 changed merging scope order to allow to unscope default scopes on association scope (rails#29611), but that caused a regression rails#38811 that accidentally allow join constraint which is required. ``` % bin/test test/cases/associations/has_many_associations_test.rb -n test_unscopes_the_default_scope_of_associated_model_when_used_with_include Run options: -n test_unscopes_the_default_scope_of_associated_model_when_used_with_include --seed 32978 # Running: E Error: HasManyAssociationsTest#test_unscopes_the_default_scope_of_associated_model_when_used_with_include: NoMethodError: undefined method `children' for nil:NilClass ~/rails/activerecord/lib/active_record/associations/join_dependency/join_association.rb:39:in `block in join_constraints' ~/rails/activerecord/lib/active_record/associations/join_dependency/join_association.rb:30:in `reverse_each' ~/rails/activerecord/lib/active_record/associations/join_dependency/join_association.rb:30:in `with_index' ~/rails/activerecord/lib/active_record/associations/join_dependency/join_association.rb:30:in `join_constraints' ~/rails/activerecord/lib/active_record/associations/join_dependency.rb:171:in `make_constraints' ~/rails/activerecord/lib/active_record/associations/join_dependency.rb:196:in `block in walk' ~/rails/activerecord/lib/active_record/associations/join_dependency.rb:196:in `each' ~/rails/activerecord/lib/active_record/associations/join_dependency.rb:196:in `flat_map' ~/rails/activerecord/lib/active_record/associations/join_dependency.rb:196:in `walk' ~/rails/activerecord/lib/active_record/associations/join_dependency.rb:90:in `block in join_constraints' ~/rails/activerecord/lib/active_record/associations/join_dependency.rb:87:in `each' ~/rails/activerecord/lib/active_record/associations/join_dependency.rb:87:in `flat_map' ~/rails/activerecord/lib/active_record/associations/join_dependency.rb:87:in `join_constraints' ~/rails/activerecord/lib/active_record/relation/query_methods.rb:1226:in `build_join_query' ~/rails/activerecord/lib/active_record/relation/query_methods.rb:1211:in `build_joins' ~/rails/activerecord/lib/active_record/relation/query_methods.rb:1091:in `build_arel' ~/rails/activerecord/lib/active_record/relation/query_methods.rb:1063:in `arel' ~/rails/activerecord/lib/active_record/relation/finder_methods.rb:419:in `block in limited_ids_for' ~/rails/activerecord/lib/active_record/relation.rb:867:in `skip_query_cache_if_necessary' ~/rails/activerecord/lib/active_record/relation/finder_methods.rb:419:in `limited_ids_for' ~/rails/activerecord/lib/active_record/relation/finder_methods.rb:398:in `apply_join_dependency' ~/rails/activerecord/lib/active_record/relation.rb:839:in `block in exec_queries' ~/rails/activerecord/lib/active_record/relation.rb:867:in `skip_query_cache_if_necessary' ~/rails/activerecord/lib/active_record/relation.rb:834:in `exec_queries' ~/rails/activerecord/lib/active_record/relation.rb:639:in `load' ~/rails/activerecord/lib/active_record/relation.rb:250:in `records' ~/rails/activerecord/lib/active_record/relation/finder_methods.rb:508:in `find_take' ~/rails/activerecord/lib/active_record/relation/finder_methods.rb:98:in `take' ~/rails/activerecord/lib/active_record/relation/finder_methods.rb:458:in `find_one' ~/rails/activerecord/lib/active_record/relation/finder_methods.rb:442:in `find_with_ids' ~/rails/activerecord/lib/active_record/relation/finder_methods.rb:69:in `find' ~/rails/activerecord/test/cases/associations/has_many_associations_test.rb:2689:in `block in <class:HasManyAssociationsTest>' bin/test test/cases/associations/has_many_associations_test.rb:2683 ``` Required join constraint should not be allowed to unscoping. Fixes rails#38811.

kamipo self-assigned this Mar 24, 2020

kamipo added the activerecord label Mar 24, 2020

kamipo mentioned this issue Apr 12, 2020

Fix unscoping association scope on joins not to raise an error #38929

Merged

kamipo closed this as completed in #38929 Apr 16, 2020

dvandersluis mentioned this issue May 13, 2020

Querying association with unscope(:where) from instance removes conditions #39275

Closed

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Association using unscope: NoMethodError: undefined method `children' for nil:NilClass #38811

Association using unscope: NoMethodError: undefined method `children' for nil:NilClass #38811

dvandersluis commented Mar 24, 2020

kamipo commented Mar 24, 2020

dvandersluis commented Mar 24, 2020

imrubyist commented Apr 1, 2020 •

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mechanicles commented Apr 1, 2020

alboyadjian commented Apr 1, 2020

dvandersluis commented Apr 1, 2020 •

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alboyadjian commented Apr 1, 2020

imrubyist commented Apr 2, 2020 •

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Association using unscope: NoMethodError: undefined method `children' for nil:NilClass #38811

Association using unscope: NoMethodError: undefined method `children' for nil:NilClass #38811

Comments

dvandersluis commented Mar 24, 2020

Steps to reproduce

Expected behavior

Actual behavior

System configuration

kamipo commented Mar 24, 2020

dvandersluis commented Mar 24, 2020

imrubyist commented Apr 1, 2020 • edited Loading

mechanicles commented Apr 1, 2020

alboyadjian commented Apr 1, 2020

dvandersluis commented Apr 1, 2020 • edited Loading

alboyadjian commented Apr 1, 2020

imrubyist commented Apr 2, 2020 • edited Loading

imrubyist commented Apr 1, 2020 •

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dvandersluis commented Apr 1, 2020 •

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imrubyist commented Apr 2, 2020 •

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