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Clean up tax rate match logic #705

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Merged
jhawthorn merged 3 commits into from Jan 20, 2016
Merged

Clean up tax rate match logic #705

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5cd4d3b
Improve logic in Spree::TaxRate.match
mamhoff Jan 16, 2016
c5e19c9
Un-xit randomly failing specs
mamhoff Jan 16, 2016
dfa3505
Update comments in tax_rate.rb
mamhoff Jan 16, 2016
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115 changes: 53 additions & 62 deletions core/app/models/spree/tax_rate.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -29,14 +29,52 @@ class TaxRate < Spree::Base

scope :by_zone, ->(zone) { where(zone_id: zone) }

# Gets the array of TaxRates appropriate for the specified order
# Finds geographically matching tax rates for an order's tax zone.
# We do not know if they are/aren't applicable until we attempt to apply these rates to
# the items contained within the Order itself.
# For instance, if a rate passes the criteria outlined in this method,
# but then has a tax category that doesn't match against any of the line items
# inside of the order, then that tax rate will not be applicable to anything.
# For instance:
#
# Zones:
# - Spain (default tax zone)
# - France
#
# Tax rates: (note: amounts below do not actually reflect real VAT rates)
# 21% inclusive - "Clothing" - Spain
# 18% inclusive - "Clothing" - France
# 10% inclusive - "Food" - Spain
# 8% inclusive - "Food" - France
# 5% inclusive - "Hotels" - Spain
# 2% inclusive - "Hotels" - France
#
# Order has:
# Line Item #1 - Tax Category: Clothing
# Line Item #2 - Tax Category: Food
#
# Tax rates that should be selected:
#
# 21% inclusive - "Clothing" - Spain
# 10% inclusive - "Food" - Spain
#
# If the order's address changes to one in France, then the tax will be recalculated:
#
# 18% inclusive - "Clothing" - France
# 8% inclusive - "Food" - France
#
# Note here that the "Hotels" tax rates will not be used at all.
# This is because there are no items which have the tax category of "Hotels".
#
# Under no circumstances should negative adjustments be applied for the Spanish tax rates.
#
# Those rates should never come into play at all and only the French rates should apply.
def self.match(order_tax_zone)
return [] unless order_tax_zone
rates = includes(zone: { zone_members: :zoneable }).load.select do |rate|
# Why "potentially"?
# Go see the documentation for that method.
rate.potentially_applicable?(order_tax_zone)
end
all_rates = includes(zone: { zone_members: :zoneable }).load

rates_for_order_zone = all_rates.select { |rate| rate.zone.contains?(order_tax_zone) }
rates_for_default_zone = all_rates.select { |rate| rate.default_vat? }

# Imagine with me this scenario:
# You are living in Spain and you have a store which ships to France.
Expand All @@ -52,16 +90,12 @@ def self.match(order_tax_zone)
#
# For further discussion, see https://github.com/spree/spree/issues/4397 and https://github.com/spree/spree/issues/4327.

remaining_rates = rates.dup
rates.each do |rate|
if rate.included_in_price?
if remaining_rates.any?{|r| r != rate && r.tax_category == rate.tax_category }
remaining_rates.delete(rate)
end
end
order_zone_tax_categories = rates_for_order_zone.map(&:tax_category)
rates_for_default_zone.delete_if do |default_rate|
order_zone_tax_categories.include?(default_rate.tax_category)
end

remaining_rates
(rates_for_order_zone + rates_for_default_zone).uniq
end

# Pre-tax amounts must be stored so that we can calculate
Expand All @@ -81,7 +115,7 @@ def self.store_pre_tax_amount(item, rates)
item.update_column(:pre_tax_amount, pre_tax_amount.round(2))
end

# This method is best described by the documentation on #potentially_applicable?
# This method is best described by the documentation on .match
def self.adjust(order_tax_zone, items)
rates = self.match(order_tax_zone)
tax_categories = rates.map(&:tax_category)
Expand All @@ -104,53 +138,6 @@ def self.adjust(order_tax_zone, items)
end
end

# Tax rates can *potentially* be applicable to an order.
# We do not know if they are/aren't until we attempt to apply these rates to
# the items contained within the Order itself.
# For instance, if a rate passes the criteria outlined in this method,
# but then has a tax category that doesn't match against any of the line items
# inside of the order, then that tax rate will not be applicable to anything.
# For instance:
#
# Zones:
# - Spain (default tax zone)
# - France
#
# Tax rates: (note: amounts below do not actually reflect real VAT rates)
# 21% inclusive - "Clothing" - Spain
# 18% inclusive - "Clothing" - France
# 10% inclusive - "Food" - Spain
# 8% inclusive - "Food" - France
# 5% inclusive - "Hotels" - Spain
# 2% inclusive - "Hotels" - France
#
# Order has:
# Line Item #1 - Tax Category: Clothing
# Line Item #2 - Tax Category: Food
#
# Tax rates that should be selected:
#
# 21% inclusive - "Clothing" - Spain
# 10% inclusive - "Food" - Spain
#
# If the order's address changes to one in France, then the tax will be recalculated:
#
# 18% inclusive - "Clothing" - France
# 8% inclusive - "Food" - France
#
# Note here that the "Hotels" tax rates will not be used at all.
# This is because there are no items which have the tax category of "Hotels".
#
# Under no circumstances should negative adjustments be applied for the Spanish tax rates.
#
# Those rates should never come into play at all and only the French rates should apply.
def potentially_applicable?(order_tax_zone)
# If the rate's zone *contains* the order's tax zone, then it's applicable.
self.zone.contains?(order_tax_zone) ||
# The rate is a VAT and its zone contains the default zone, then it's applicable.
(self.included_in_price? && self.zone.contains?(Spree::Zone.default_tax))
end

# Creates necessary tax adjustments for the order.
def adjust(order_tax_zone, item)
amount = compute_amount(item)
Expand Down Expand Up @@ -185,6 +172,10 @@ def default_zone_or_zone_match?(order_tax_zone)
Zone.default_tax.try!(:contains?, order_tax_zone) || self.zone.contains?(order_tax_zone)
end

def default_vat?
included_in_price && zone.contains?(Spree::Zone.default_tax)
end

private

def create_label
Expand Down
7 changes: 3 additions & 4 deletions core/spec/models/spree/tax_rate_spec.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -360,8 +360,7 @@
expect(line_item.adjustments.tax.count).to eq(1)
end

# This test fails intermittently - it's a matter of luck
xit 'has 4.79 of included tax' do
it 'has 4.79 of included tax' do
expect(line_item.included_tax_total).to eq(4.79)
end

Expand All @@ -382,8 +381,8 @@
expect(line_item.adjustments.tax.count).to eq(1)
end

# Fails intermittently - xit'ed for the time being
xit 'has 2.02 of included tax' do
it 'has 2.02 of included tax' do
pending 'waiting for the MOSS refactoring'
expect(line_item.included_tax_total).to eq(2.02)
end

Expand Down