Spree::Promotion::Rules::Taxon is deprecated and will be rem

Error message

Spree::Promotion::Rules::Taxon is deprecated and will be removed in Spree 6.1. Use Spree::Promotion::Rules::Category instead.

What it means

In Spree 6.0 the taxon-based promotion rule was renamed to Spree::Promotion::Rules::Category. The file promotion/rules/taxon.rb now contains only a true constant alias (`Taxon = Category`) plus a Spree::Deprecation.warn that fires when the file loads — not when a method is called. Old STI type strings ('Spree::Promotion::Rules::Taxon') still instantiate correctly through the alias until the 6.0 data migration rewrites them; the alias is removed in 6.1.

Source

Thrown at spree/core/app/models/spree/promotion/rules/taxon.rb:13

# frozen_string_literal: true

module Spree
  class Promotion
    module Rules
      # Deprecation alias for Spree::Promotion::Rules::Category, renamed from
      # Spree::Promotion::Rules::Taxon in 6.0. A true constant alias, so old STI type
      # strings (`'Spree::Promotion::Rules::Taxon'`) still instantiate correctly until
      # the Phase 4 migration rewrites them. The warning fires when this file loads.
      # Removed in 6.1.
      Taxon = Category

      Spree::Deprecation.warn('Spree::Promotion::Rules::Taxon is deprecated and will be removed in Spree 6.1. Use Spree::Promotion::Rules::Category instead.')
    end
  end
end

View on GitHub (pinned to 06bf66a868)

Solutions

Replace every code reference to `Spree::Promotion::Rules::Taxon` with `Spree::Promotion::Rules::Category` (grep the app, initializers, factories, specs, and `class_name:` options).
Run the 6.0 taxon→category data migration so promotion rule STI `type` values are rewritten to the Category class string — after that no old-type row loads the alias.
Update extensions/decorators that reference or subclass the old constant to their 6.0-compatible releases.
If the warning appears only at boot from eager loading and no references remain, silence it temporarily with `Spree::Deprecation.silence { Spree::Promotion::Rules::Taxon }`-style wrapping or accept the log noise until 6.1 — but verify the DB has no legacy type strings first.

Example fix

# before
rule = Spree::Promotion::Rules::Taxon.new

# after
rule = Spree::Promotion::Rules::Category.new

Defensive patterns

Strategy: validation

Validate before calling

# Check for legacy STI type strings that instantiate the alias:
Spree::PromotionRule.where(type: 'Spree::Promotion::Rules::Taxon').exists?

# Check for code references (run in shell):
# grep -rn "Promotion::Rules::Taxon" app/ lib/ config/ spec/ --exclude-dir=tmp

# Fail on load-time deprecations in CI:
Spree::Deprecation.behavior = :raise

Prevention

After a rename-heavy Spree upgrade, grep for the old constant everywhere including class_name: options and factories.
Run the shipped data migrations immediately on upgrade so legacy STI type strings stop instantiating deprecated aliases.
Remember eager loading fires file-load warnings at boot with zero references — don't burn time hunting phantom callers before checking eager_load.

When it happens

Trigger: Anything that causes app/models/spree/promotion/rules/taxon.rb to load: referencing `Spree::Promotion::Rules::Taxon` in code, `type: 'Spree::Promotion::Rules::Taxon'` rows being instantiated (promotion rules table STI), factories/seeds using the old class, or production eager-loading every file under app/models at boot. In development it fires on first reference; with `config.eager_load = true` it fires at boot even with no explicit reference.

Common situations: Upgrading to Spree 6.0 with promotion_rule rows whose STI `type` still says 'Spree::Promotion::Rules::Taxon' (data migration not yet run), extensions/decorators referencing the old constant, or old specs/factories. Also appears as boot-time noise in production logs purely from eager load.

Related errors

AI-assisted analysis of spree/spree@06bf66a868 (2026-08-21). Data as JSON: /api/errors/ccf784eff1b67e99. Report an issue: GitHub.