fix: cascade parent category color changes to subcategories

[RealDiligent]

Fixes #2816

Problem

A subcategory's color does not follow its parent. After you change a parent category's color, the subcategory keeps its old color, so the two visibly mismatch and there's no way to correct the subcategory from the UI (subcategory colors are driven by the parent).

Root cause

Category already forces a subcategory to adopt its parent's color, but only via a before_save hook on the subcategory:

before_save :inherit_color_from_parent   # self.color = parent.color if subcategory?

Changing a parent's color saves only the parent record — the subcategories are never re-saved, so their stored color column stays at the old value.

Fix

Add an after_update hook so a parent's color change cascades to its subcategories:

after_update :sync_subcategory_colors, if: :saved_change_to_color?

def sync_subcategory_colors
  subcategories.where.not(color: color).update_all(color: color)
end

• Runs only when color actually changed (saved_change_to_color?).
• where.not(color: color) skips rows already in sync, so it's a no-op when nothing changes.
• Leaf categories have no subcategories, so it's a harmless no-op for them.
• update_all is a single UPDATE — no per-row callbacks or N extra saves.

Combined with the existing before_save, subcategory colors now stay consistent with their parent in both directions.

Tests

Added to test/models/category_test.rb:

• changing a parent's color cascades to its subcategories;
• changing the color of a category with no subcategories does not error.

Impact / risk

• Fixes the visible color mismatch; no schema or API changes.
• Scoped to Category (+1 hook, +1 method, +2 tests).

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes

  • Updating a category’s color now automatically applies the new color to its existing subcategories.
  • Categories without subcategories can be updated without errors.

• Tests

  • Added coverage for cascading color updates and standalone category color changes.

[coderabbitai]

📝 Walkthrough

Walkthrough

Category color updates now trigger synchronization of differing stored subcategory colors. Tests cover propagation to subcategories and successful updates for categories without subcategories.

Changes

Category color synchronization

Layer / File(s)	Summary
Cascade category colors and validate updates app/models/category.rb, test/models/category_test.rb	An after_update callback detects category color changes and bulk-updates associated subcategories with differing colors. Tests cover propagation and standalone category updates.

Estimated code review effort: 2 (Simple) | ~10 minutes

Suggested reviewers: bittensorrider, chkfail

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: cascading parent category color updates to subcategories.
Linked Issues check	✅ Passed	The PR implements the requested behavior so sub-category colors automatically follow parent category color changes.
Out of Scope Changes check	✅ Passed	The changes are limited to the color-cascade fix and matching tests, with no obvious unrelated additions.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@app/models/category.rb`:
- Line 22: Update the instruction text in the category update behavior within
update_category so it states that parent color changes cascade to subcategories,
removing the outdated claim that they do not. Keep the surrounding assistant
behavior guidance unchanged.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 3deed5ea-e4c0-42c0-a42d-5fd25fc3284e

📥 Commits

Reviewing files that changed from the base of the PR and between c9a28e1 and 954fc4a.

📒 Files selected for processing (2)

• app/models/category.rb
• test/models/category_test.rb

[coderabbitai]

🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win

Update the assistant behavior contract.

app/models/assistant/function/update_category.rb lines 8-14 still says parent color changes do not cascade, which is now false. Update that instruction so the assistant does not give callers incorrect behavior expectations.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@app/models/category.rb` at line 22, Update the instruction text in the
category update behavior within update_category so it states that parent color
changes cascade to subcategories, removing the outdated claim that they do not.
Keep the surrounding assistant behavior guidance unchanged.

[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: 954fc4aff1

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[chatgpt-codex-connector]

Index parent_id before cascading colors

On installations with many families, every parent color edit now runs an UPDATE filtered by categories.parent_id, but the categories table has no index on parent_id (db/schema.rb only indexes family_id). PostgreSQL therefore scans the entire cross-tenant categories table while the parent transaction remains open, even when the category has no children. Add a parent_id index or scope the update by family_id so the existing index can bound the scan.

Useful? React with 👍 / 👎.

[jjmata]

Small, well-targeted fix. The root-cause analysis is correct: the existing before_save :inherit_color_from_parent only fires when the subcategory itself is saved, so a parent-only color change never touched the child row. The new after_update :sync_subcategory_colors, if: :saved_change_to_color? closes that gap with a single update_all, which correctly bypasses callbacks/validations and skips already-in-sync rows via where.not(color: color).

Since category_level_limit caps the hierarchy at parent → subcategory (no grandchildren), one level of cascade is sufficient here — worth confirming that assumption still holds if the depth limit ever changes, but not a concern today. Tests cover both the cascade and the no-subcategories no-op case. No issues found.

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