MONGOID-5934 Fix NoMethodError in nested attributes when raise_not_found_error is false

[comandeo-mongo]

With Mongoid.raise_not_found_error = false, a nested-attributes hash referencing a non-existent _id on a has_and_belongs_to_many association (or any association when allow_reparenting_via_nested_attributes is enabled) crashed with NoMethodError: undefined method 'update_attributes' for nil.

Nested::Many#update_nested_relation looks the document up with association.klass.unscoped.find(converted). find honors raise_not_found_error and returns nil when the flag is off, and the nil flowed straight into update_document. The other two not-found branches in the same method raise Errors::DocumentNotFound unconditionally, and ActiveRecord likewise raises RecordNotFound for unmatched nested ids regardless of configuration, so this branch now does the same: a nil from find raises Errors::DocumentNotFound.

Behavior with raise_not_found_error = true is unchanged: find raises before the new guard is reached, with the same exception class and message.

Changes:

• lib/mongoid/association/nested/many.rb: nil guard after the find in the HABTM/reparenting branch, raising Errors::DocumentNotFound.
• spec/mongoid/attributes/nested_spec.rb: new contexts for has_many (with reparenting enabled) and has_and_belongs_to_many with a non-existent id, each covering raise_not_found_error true (regression guard) and false (failed with NoMethodError before the fix).

Test plan (all against a local 3-node replica set):

• spec/mongoid/attributes/nested_spec.rb — 713 examples, 0 failures (new examples fail with NoMethodError before the fix)
• Regression sweep: spec/mongoid/attributes, spec/mongoid/attributes_spec.rb, spec/mongoid/association/nested, spec/mongoid/association/referenced/has_and_belongs_to_many, spec/mongoid/association/referenced/has_many, spec/mongoid/association/embedded, spec/mongoid/persistable — 6028 examples, 0 failures, 13 pending (pre-existing)
• bundle exec rubocop on changed files — no offenses

MONGOID-5934

[Copilot]

Pull request overview

Fixes a crash in nested-attributes processing when Mongoid.raise_not_found_error = false, by ensuring a missing related document in the HABTM / reparenting code path raises Mongoid::Errors::DocumentNotFound rather than flowing nil into update_document.

Changes:

• Add a nil guard after association.klass.unscoped.find(...) in Nested::Many#update_nested_relation, raising Errors::DocumentNotFound when the document is missing.
• Add RSpec coverage for missing nested ids for both has_many (with reparenting enabled) and has_and_belongs_to_many, under both raise_not_found_error settings.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
lib/mongoid/association/nested/many.rb	Adds a guard to raise DocumentNotFound when find returns nil in the HABTM/reparenting branch.
spec/mongoid/attributes/nested_spec.rb	Adds regression specs covering missing nested ids with raise_not_found_error both true and false.

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