Indico Group Registration

Participant-run group registration with plan-based discounts for Indico 3.3.

A participant picks a group plan while registering, gets a code and a join link, and shares them however they like. Everyone who joins pays that plan's rate straight away. The group confirms itself the moment the plan's seat count is filled — there is no button to press. If it never fills, the plugin reprices it at the reconciliation deadline and reports what each member still owes.

Organizers set the plans and the disclaimer. They never have to create a group.

How it works

Plans

An organizer defines plans per registration form. A plan is a seat count and a rate:

[
  {"id": "p3",  "label": "Group of 3",  "size": 3,  "type": "percent", "value": 10},
  {"id": "p10", "label": "Group of 10", "size": 10, "type": "percent", "value": 15},
  {"id": "p25", "label": "Group of 25", "size": 25, "type": "amount",  "value": 50}
]

The seat count is both the target and the cap: filling it confirms the group, and the group is then full.

Lifecycle

The only transition a human triggers is dissolution.

Reconciliation, and the one thing to know before enabling this

Members may pay before their group fills. If the group then falls short, the plugin reprices everyone — including people who have already paid.

Indico has no concept of a partial payment or a balance. A transaction is one amount against one registration, and its checkout would charge the whole new price again rather than the difference. So an already-paid member whose price rises stays complete as far as Indico is concerned, and only this plugin knows they owe anything.

The plugin gives organizers a Balances due list (paid amount, new price, delta) and e-mails every affected member, but a person collects the money — at the desk or by transfer, recorded as a manual payment. Two settings soften it:

• set the reconciliation deadline well before the event, so balances surface while there is still time to chase them;
• turn off allow early payment if you would rather not chase anyone.

Sharing a group

The group panel shows the group code and the join link, each with a copy button. The plugin sends no invitations. There is no invite box and no way for a participant to make your server e-mail a stranger. Leaders share the link themselves.

The plugin does send e-mails that nobody can trigger on demand: group confirmed, group short with the new rate, and group dissolved.

Installation

Do not let pip upgrade Indico by accident. This plugin declares indico>=3.3,<3.4, and pip will happily upgrade an installed Indico to satisfy that. An Indico whose code is newer than its database fails on every page that touches a migrated table — the whole site, not just registration. Install into the existing Indico virtualenv and check what pip says it is about to do:

/opt/indico/.venv/bin/pip install indico-plugin-group-registration

If Indico appears in the "Installing collected packages" line, run the core migrations before restarting (see below). To keep pip away from Indico entirely:

/opt/indico/.venv/bin/pip install --no-deps indico-plugin-group-registration

Add it to indico.conf:

PLUGINS = {'group_registration'}

Then migrate. --all-plugins runs core migrations too, which is what you want — if pip moved Indico forward, this is the step that moves the database with it:

indico db --all-plugins upgrade

Sanity-check that nothing is pending:

indico db alembic current   # should match
indico db alembic heads

Build the assets:

python bin/maintenance/build-assets.py plugin /path/to/IndicoGroupRegistration

Restart Indico and its Celery workers — the reconciliation task runs every fifteen minutes from the Celery beat schedule.

If the site is throwing UndefinedColumn errors

Indico's code is ahead of its database. Nothing to do with this plugin's tables; run the migrations:

indico db --all-plugins upgrade

Or put Indico back where it was and migrate later:

/opt/indico/.venv/bin/pip install 'indico==<your previous version>'

Configuration

Event management → Group registration, then pick a registration form. Nothing changes on a form until group registration is enabled for it.

Enabling group registration provisions two fields on the form:

• ext__group_plan — the plan picker the participant fills in. Put it wherever you like in the form.
• ext__group_discount — a manager-only field carrying the discount. It is locked, written only by the plugin, and appears as a named line on the invoice. Leave it alone; the plugin puts it back if it is removed.

Development

pip install -e '.[dev]'
pytest
ruff check .

The tests here are unit tests over the money arithmetic and the code handling; they do not need a database or Indico's pytest plugin.

How it hooks into Indico

Nothing in core is patched. See docs/EXTENSION-POINTS.md for the full map with file-and-line references, and docs/PLAN.md for the design. The short version:

• registration field types via signals.core.get_fields
• the registration lifecycle via registration_created, registration_deleted and registration_state_updated
• is_field_data_locked to keep core out of the plugin's own field
• registrant_list_items for the Group column
• before-render-registration-info for the group panel
• the React field registry via regformCustomFields
• get_template_customization_paths to name the discount on the checkout page, using {% extends '~...' %} so it inherits the core template rather than forking it

Licence

MIT.