feat: Add `dependent: :adopt` option for `has_closure_tree` #471

vsmay98 · 2025-11-22T10:32:32Z

Summary

This PR adds a new dependent: :adopt option to has_closure_tree that automatically moves children to their grandparent when a parent node is destroyed. If the node being destroyed is a root (has no grandparent), children become root nodes instead.

Motivation

When working with hierarchical data structures, there are scenarios where you want to remove intermediate nodes while preserving the tree structure. The existing dependent options (:nullify, :destroy, :delete_all) don't provide this behavior:

:nullify makes all children root nodes, which can break tree relationships
:destroy and :delete_all remove the entire subtree, which may not be desired

The :adopt option fills this gap by maintaining tree continuity when removing nodes, which is particularly useful for:

Category hierarchies: When removing a category, its subcategories should move up to the parent category
Organizational structures: When a department is dissolved, its teams should be reassigned to the parent department
File systems: When a folder is deleted, its contents should move to the parent folder
Menu structures: When a menu item is removed, its sub-items should be promoted to the parent level

Example Usage

class Category < ApplicationRecord
  has_closure_tree dependent: :adopt, name_column: 'name'
end

# Create a hierarchy: Electronics -> Computers -> Laptops -> Gaming Laptops
root = Category.create!(name: 'Electronics')
computers = Category.create!(name: 'Computers', parent: root)
laptops = Category.create!(name: 'Laptops', parent: computers)
gaming = Category.create!(name: 'Gaming Laptops', parent: laptops)

# Remove the intermediate "Laptops" category
laptops.destroy

# Gaming Laptops is now directly under Computers
gaming.reload
computers.reload
gaming.parent == computers  # => true
gaming.ancestry_path         # => ["Electronics", "Computers", "Gaming Laptops"]

Behavior

When destroying a node with a parent (grandparent exists): All children are moved to the grandparent
When destroying a root node (no grandparent): All children become root nodes
Hierarchy maintenance: The closure table is automatically rebuilt for each adopted child to maintain correct ancestor/descendant relationships
Deep nesting: Works correctly with deeply nested structures - only immediate children are adopted, maintaining their own subtree structure

Implementation Details

Association Setup: The has_many :children association uses :nullify when dependent: :adopt is set (since ActiveRecord doesn't support :adopt directly), but the actual adoption logic is handled in the before_destroy callback.
Adoption Logic: The adopt_children_to_grandparent method:
- Retrieves the grandparent ID (or nil for root nodes)
- Finds all children of the node being destroyed
- Updates each child's parent_id to the grandparent ID
- Rebuilds the hierarchy for each child to maintain closure table integrity
Order of Operations: Adoption happens before hierarchy references are deleted to ensure children can be properly identified and updated.

Backward Compatibility

This change is fully backward compatible. The new :adopt option is optional and doesn't affect existing behavior. All existing dependent options (:nullify, :destroy, :delete_all, nil) continue to work as before.

vsmay98 · 2025-11-22T10:38:32Z

@seuros
This PR is ready for review. Please take a look when you get a chance and share your thoughts. Thanks!

seuros · 2025-11-22T10:49:37Z

Love this feature. I can see the pattern used by many cases.

The test need to assert that the hierarchy table was mutated, and that it work with the 3 adapters.

seuros · 2025-12-06T22:12:35Z

@vsmay98 you will finish the pr ?

vsmay98 · 2025-12-09T05:39:54Z

Yeah @seuros , I haven’t had much time recently, but I’ll try to finish this PR soon. I was having some trouble running the MySQL specs locally and needed to look into it.

seuros · 2025-12-09T06:01:07Z

Docker

… hierarchy

vsmay98 · 2025-12-10T07:46:37Z

Thanks @seuros
The PR is ready for review

Copilot

Pull request overview

This PR introduces a new dependent: :adopt option for has_closure_tree, enabling intermediate nodes to be removed while preserving tree structure by moving children to their grandparent. This fills a gap between the existing :nullify (which makes all children root nodes) and :destroy/:delete_all (which remove entire subtrees).

Key Changes:

Added adoption logic that reassigns children to their grandparent (or makes them root nodes if no grandparent exists) before destroying a node
Enhanced the Arel helpers with a to_sql_with_connection method to ensure proper SQL quoting across different database adapters
Comprehensive test coverage across PostgreSQL, MySQL, and SQLite databases

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
lib/closure_tree/hierarchy_maintenance.rb	Implements `adopt_children_to_grandparent` method that updates children's parent_id and rebuilds their hierarchies before node destruction
lib/closure_tree/association_setup.rb	Maps `:adopt` to `:nullify` for the `children` association since ActiveRecord doesn't support `:adopt` natively, with adoption handled by callback
lib/closure_tree/arel_helpers.rb	Adds `to_sql_with_connection` helper to convert Arel queries with proper database-specific quoting
lib/closure_tree/support.rb	Updates documentation comment to include `:adopt` as a valid dependent option
README.md	Documents the new `:adopt` option with clear explanation of its behavior and use cases
test/closure_tree/adopt_test.rb	Comprehensive test suite covering adoption scenarios: grandparent adoption, root node destruction, multiple children, deep nesting, and integration with existing methods
test/dummy/app/models/adoptable_tag.rb	Test model for PostgreSQL using `:adopt` option
test/dummy/app/models/mysql_adoptable_tag.rb	Test model for MySQL using `:adopt` option
test/dummy/app/models/memory_adoptable_tag.rb	Test model for SQLite using `:adopt` option
test/dummy/db/schema.rb	Schema definitions for adoptable_tags test tables across all database types
test/dummy/db/sqlite_schema.rb	SQLite-specific schema for memory_adoptable_tags table
test/dummy/db/secondary_schema.rb	MySQL-specific schema for mysql_adoptable_tags table

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Copilot · 2025-12-10T12:30:17Z

test/dummy/app/models/adoptable_tag.rb

+
+

This file has two blank lines at the end instead of one. Per the codebase convention, Ruby files should end with exactly one blank line. Remove the extra blank line.

Suggested change

Copilot · 2025-12-10T12:30:17Z

test/dummy/app/models/memory_adoptable_tag.rb

+class MemoryAdoptableTag < SqliteRecord
+  has_closure_tree dependent: :adopt, name_column: 'name'
+end
+


This file has two blank lines at the end instead of one. Per the codebase convention, Ruby files should end with exactly one blank line. Remove the extra blank line.

Suggested change

Copilot · 2025-12-10T12:30:17Z

test/dummy/app/models/mysql_adoptable_tag.rb

+class MysqlAdoptableTag < MysqlRecord
+  has_closure_tree dependent: :adopt, name_column: 'name'
+end
+


This file has two blank lines at the end instead of one. Per the codebase convention, Ruby files should end with exactly one blank line. Remove the extra blank line.

Suggested change

Copilot · 2025-12-10T12:30:18Z

test/closure_tree/adopt_test.rb

+      assert_equal p2, p3.parent
+
+      hierarchy = model_class.hierarchy_class
+      initial_p2_hierarchies = hierarchy.where(ancestor_id: p2.id).count


This assignment to initial_p2_hierarchies is useless, since its value is never read.

Suggested change

initial_p2_hierarchies = hierarchy.where(ancestor_id: p2.id).count

Copilot · 2025-12-10T12:30:18Z

test/closure_tree/adopt_test.rb

+
+      hierarchy = model_class.hierarchy_class
+      initial_p2_hierarchies = hierarchy.where(ancestor_id: p2.id).count
+      initial_p3_hierarchies = hierarchy.where(descendant_id: p3.id).count


This assignment to initial_p3_hierarchies is useless, since its value is never read.

Suggested change

initial_p3_hierarchies = hierarchy.where(descendant_id: p3.id).count

Copilot · 2025-12-10T12:30:18Z

test/closure_tree/adopt_test.rb

+      leaf = model_class.create!(name: 'leaf', parent: p2)
+
+      hierarchy = model_class.hierarchy_class
+      initial_count = hierarchy.count


This assignment to initial_count is useless, since its value is never read.

Suggested change

initial_count = hierarchy.count

seuros · 2025-12-10T13:29:38Z

@vsmay98 pretty close, the linter and the unused code.

Add dependent: :adopt option for has_closure_tree

7a5d11f

seuros changed the title ~~Add dependent: :adopt option for has_closure_tree~~ feat: Add dependent: :adopt option for has_closure_tree Nov 22, 2025

add test for mysql and sqlite adapters

663c2a9

Add SQL conversion method for Arel AST and optimize child adoption in…

da2c379

… hierarchy

seuros requested a review from Copilot December 10, 2025 12:21

Copilot started reviewing on behalf of seuros December 10, 2025 12:22 View session

Copilot AI reviewed Dec 10, 2025

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seuros approved these changes Dec 10, 2025

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feat: Add dependent: :adopt option for has_closure_tree #471

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vsmay98 commented Nov 22, 2025

Summary

Motivation

Example Usage

Behavior

Implementation Details

Backward Compatibility

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vsmay98 commented Nov 22, 2025

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seuros commented Nov 22, 2025

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seuros commented Dec 6, 2025

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vsmay98 commented Dec 9, 2025

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seuros commented Dec 9, 2025

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vsmay98 commented Dec 10, 2025

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seuros commented Dec 10, 2025

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feat: Add `dependent: :adopt` option for `has_closure_tree` #471

feat: Add `dependent: :adopt` option for `has_closure_tree` #471