fix: Remove ActiveRecord::Dirty to preserve nested document changes on save

[pimpin]

Problem

When modifying nested documents and calling save(), changes were incorrectly reset, causing data loss. This happened because ActiveRecord::Dirty's changes_applied callback cleared attribute changes prematurely.

Reproduction:

obj.others[0].name = "foo"
obj.others[1].child = SubTypeTest.new(name: "baz")
obj.save!

# BUG: Nested changes were lost! ❌
obj.others[0].name  # => nil (expected: "foo")
obj.others[1].child # => nil (expected: SubTypeTest)

Solution

Remove dependency on ActiveRecord::Dirty and implement custom change tracking that properly handles nested documents.

What changed:

1. Removed ActiveRecord::Dirty inclusion from Document base class
2. Disabled super call in changes_applied to prevent premature change clearing
3. Added proper type casting at assignment time to match ActiveRecord behavior:

   # Cast → Serialize → Cast cycle ensures consistent nested object handling
   casted_value = type.cast(type.serialize(type.cast(new_attribute_value)))

4. Preserved change tracking API (changed?, changes, etc.) through custom implementation

Benefits:

• ✅ Nested document changes persist correctly after save
• ✅ Type casting happens at assignment time (consistent with AR)
• ✅ Maintains backward compatibility with change tracking API
• ✅ Reduces dependency footprint

Testing

• ✅ All existing specs pass
• ✅ Added regression tests for nested document changes
• ✅ Validated in production environment (Doctolib monolith with 150+ engines)
  • CI run: https://github.com/doctolib/doctolib/pull/192171

Breaking Changes

⚠️ This PR removes ActiveRecord::Dirty as a dependency.

Impact Analysis:

• Low risk: The public change tracking API (changed?, changes, changed_attributes, etc.) remains functional through custom implementation
• Potential issue: Code that explicitly relies on ActiveRecord::Dirty-specific internals (private methods, modules) may break
• Mitigation: Most applications use only the standard change tracking API which continues to work

Recommendation: Review your codebase for any direct usage of ActiveRecord::Dirty internals before upgrading.

Checklist

• CI is green
• Regression tests added
• Tested in large production application

Related

• Complements Add support for ignored_properties on NestedDocument #20 (ignored_properties support for nested documents, already in main)

[pimpin]

Thanks to Claude, we get a green inplem according to CI. Let's check in Docto CI that this implem is not breaking smth.

[Copilot]

Pull Request Overview

This PR removes ActiveRecord::Dirty usage to fix a bug where nested resource changes were being reset on save operations. The change replaces the ActiveRecord::Dirty dependency with a custom implementation to handle change tracking properly for nested resources.

• Removes ActiveModel::Dirty inclusion and replaces with custom Changeable module
• Modifies changes_applied method to prevent unwanted change resets
• Adds test coverage for the nested resource change preservation bug

Reviewed Changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
lib/couchbase-orm/base.rb	Removes ActiveModel::Dirty inclusion, keeping only custom Changeable module
lib/couchbase-orm/changeable.rb	Removes call to super in changes_applied to prevent change resets
lib/couchbase-orm/types/timestamp.rb	Adds .floor calls to timestamp casting for consistency
spec/type_spec.rb	Adds cast method to DateTimeWith3Decimal test class
spec/type_nested_spec.rb	Adds test cases to verify nested resource changes are preserved after save

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