Auto-create Students and Coaches groups when a new chapter is created

[mroderick]

Background

Groups were introduced in 2014 (commit e681a26) as a way to organise chapter membership into two categories: Students and Coaches. Every chapter has conventionally required exactly these two groups. Issue #510 (2016) validated this by restricting Group::NAMES to only %w[Coaches Students].

Problem

Creating a chapter via /admin/chapters/new does not automatically create the required groups. An admin must then manually visit /admin/groups/new twice — once for Students, once for Coaches — and pick the new chapter from a dropdown. If this step is missed:

• Members visiting the chapter page see no subscription buttons (chapter/_subscriptions.html.haml iterates @chapter.groups)
• Workshop invitations silently send to zero members (InvitationManager#chapter_students / #chapter_coaches query empty relations)
• The admin chapter show page shows no group stats

This is a foot-gun. The chapter_with_groups fabricator already auto-creates groups in tests/seeds (db/seeds.rb uses it for every chapter), so the codebase already assumes this pattern.

Evidence

Production DB (codebar_production_dump):

• 54 chapters
• 108 groups
  → Exactly 2 groups per chapter, confirming the invariant holds in practice.

Proposed solution

A service object in app/services/chapter_creation_service.rb that wraps chapter + groups in a single transaction:

class ChapterCreationService
  Result = Struct.new(:chapter, :success, :errors, keyword_init: true)

  def self.call(params)
    chapter = Chapter.new(params)

    ActiveRecord::Base.transaction do
      chapter.save!
      chapter.groups.create!(name: 'Students')
      chapter.groups.create!(name: 'Coaches')
    end

    Result.new(chapter: chapter, success: true)
  rescue ActiveRecord::RecordInvalid => e
    Result.new(chapter: chapter, success: false, errors: e.message)
  end
end

Controller change: Admin::ChaptersController#create calls the service:

def create
  result = ChapterCreationService.call(chapter_params)
  @chapter = result.chapter
  authorize(@chapter)

  if result.success
    flash[:notice] = "Chapter #{@chapter.name} has been successfully created"
    redirect_to [:admin, @chapter]
  else
    flash[:notice] = @chapter.errors.full_messages
    render 'new'
  end
end

Why a service object:

• Single SQL transaction — if groups fail, chapter is rolled back
• Controller stays thin (coordinator, not business logic)
• Testable in isolation with unit tests
• Reusable if other entry points need chapter creation (seeds, API, console)
• No hidden model callbacks — the side effect is explicit at the call site

Follow-up: remove manual group creation UI

Once this proposal is accepted, the groups new/create flow becomes dead code and can be removed as a follow-up PR:

What becomes unnecessary

• app/views/admin/groups/new.html.haml — the form for manually creating a group and picking its chapter from a dropdown. This is the last place the admin/groups Chosen select exists.
• Admin::GroupsController#new and #create — no admin should ever need to create a group by hand.
• app/views/layouts/_admin_menu.html.haml:28 — the "New group" link in the admin menu.

What stays

• Admin::GroupsController#show — viewing group members, eligible counts, and subscriptions is still useful.
• app/models/group.rb and all its scopes — groups are still the core entity for subscriptions and invitations.
• chapter_with_groups fabricator — can be folded into the base chapter fabricator, since every chapter now always has groups.

Why this matters for the Chosen cleanup

The admin/groups/new page contains a f.association :chapter that gets Chosen-enhanced by the global init. Removing this page eliminates one more <select> from the site and brings us closer to dropping Chosen entirely.

Related

• Issue Validate Group names #510 — validated group names to only "Students" / "Coaches"
• Commit e681a26 — original chapters and groups creation

[mroderick]

@KimberleyCook @olleolleolle: what do you think about this one? Shall I go ahead and make the improvements?

[mroderick]

Both PRs have been merged. Closing this.