Add solidus/tax_category_deprecated warning cop

changelog/new_add_solidus_tax_category_deprecated.md

@@ -0,0 +1 @@
+* [#x](https://github.com/solidusio/rubocop-solidus/pull/x): Add solidus/tax_category_deprecated warning cop. ([@safafa][])

config/default.yml

@@ -73,3 +73,9 @@ Solidus/SpreeTDeprecated:
   Enabled: true
   VersionAdded: '0.1'
   Reference: 'https://github.com/solidusio/rubocop-solidus/issues/22'
+
+Solidus/TaxCategoryDeprecated:
+  Description: 'Checks if tax_category is being used and issue a warning'
+  Enabled: true
+  VersionAdded: '<<next>>'
+  Reference: 'https://github.com/solidusio/rubocop-solidus/issues/25'

lib/rubocop/cop/solidus/tax_category_deprecated.rb

@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Solidus
+      # This cop finds .tax_category occurrences and suggest using .tax_categories instead.
+      #
+      # @example
+      #
+      #   # bad
+      #     model.tax_category = data
+      #
+      #   # good
+      #     model.tax_categories = [data]
+      #
+      #
+      #
+      class TaxCategoryDeprecated < Base
+        include TargetSolidusVersion
+        minimum_solidus_version 2.2
+
+        MSG = 'If you are Using Taxrate model use `.tax_categories = [data]` instead of `.tax_category = data`'
+
+        def_node_matcher :existing_tax_category?, <<~PATTERN
+          (send ... :tax_category)
+        PATTERN
+
+        def on_send(node)
+          return unless existing_tax_category?(node)
+
+          add_offense(node, severity: :warning)
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/solidus_cops.rb

@@ -13,3 +13,4 @@
 require_relative 'solidus/spree_icon_deprecated'
 require_relative 'solidus/spree_refund_call_perform'
 require_relative 'solidus/spree_t_deprecated'
+require_relative 'solidus/tax_category_deprecated'

spec/rubocop/cop/solidus/tax_category_deprecated_spec.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::Solidus::TaxCategoryDeprecated, :config do
+  let(:config) { RuboCop::Config.new }
+  it 'registers an offense when using `tax_category`' do
+    expect_offense(<<~RUBY)
+      model.tax_category
+      ^^^^^^^^^^^^^^^^^^ Solidus/TaxCategoryDeprecated: If you are Using Taxrate model use `.tax_categories = [data]` instead of `.tax_category = data`
+    RUBY
+  end
+
+  it 'does not register an offense when using `tax_categories`' do
+    expect_no_offenses(<<~RUBY)
+      model.tax_categories
+    RUBY
+  end
+end