Fix thousand separator issue in validation

[RubenIgnacio]

When validating a model with a monetized field retrieved from the database, a validation error is raised if the field is not set before the model is validated when a validation with a limit is applied, regardless of whether the monetized field already has a value. For example:

class Product < ActiveRecord::Base
  monetize :price_cents, numericality: { less_than_or_equal_to: 1000 }
end

This issue occurs specifically with currencies that use a dot (.) as a thousand separator, such as EUR. Consider a scenario where a product with a price of 1,200 EUR is retrieved from the database. When attempting to validate it, a validation error occurs due to the numericality limit:

product = Product.find(1) # <Product id: 1, price_cents: 120000, price_currency: "EUR">
product.valid? # => false

# However, if the price is set before validation, the operation succeeds:
product.price = 1200
product.valid? # => true

During the validation process, the MoneyValidator#validate_each method is invoked to verify whether raw_value.nil? && record.public_send(subunit_attr) is true. When this condition is true, raw_value is calculated as subunit_value.to_f / currency.subunit_to_unit, resulting in a float value.

Subsequently, when the generate_details method is called, it determines the currency's thousand separator in order to instantiate the Details object. For currencies that use a dot (.) as a thousand separator, the Details object, when passed to the normalize method, converts the raw_value to a string and removes the thousand separator.

This conversion process results in the original float value of 120.0 for raw_value being transformed into the string '120.0'. However, after the thousand separator is removed, this string is misinterpreted as '12000', ultimately resulting in a validation failure when a numericality limit is enforced.

Proposed Solution

Replace the following code:

# WARNING: Currently this is only defined in ActiveRecord extension!
before_type_cast = :"#{attr}_money_before_type_cast"
raw_value = record.try(before_type_cast)

# If raw value is nil and changed subunit is nil, then
# nil is a assigned value, else we should treat the
# subunit value as the one assigned.
if raw_value.nil? && record.public_send(subunit_attr)
  subunit_value = record.public_send(subunit_attr)
  raw_value = subunit_value.to_f / currency.subunit_to_unit
end

with this code:

# WARNING: Currently this is only defined in ActiveRecord extension!
before_type_cast = :"#{attr}_money_before_type_cast"
raw_value = record.try(before_type_cast) || record.public_send(attr)

This change ensures that if the before_type_cast attribute is nil, the method will call the attribute directly to retrieve the current value. Since the retrieved value is a Money object, it is correctly formatted when converted to a string, avoiding the issue caused by misinterpretation of the thousand separator.

Changes included in this PR:

• Organize monetizable specs to improve readability.
• Add tests to validate a monetizable field that uses a currency with a dot as a thousand separator.
• Fix the issue when validating a monetizable field that uses a currency with a dot as a thousand separator.

[sunny]

My two cents: I prefer longer specs to the extra indirection of adding these custom expectation methods. But I understand that this is quite a personal preference.

[RubenIgnacio]

Well, maybe I got a little carried away when I wrote all these changes. But I think I wanted them to be reusable and only require a single method call, at least for simple cases. I could still remove them if it's too much.

[sunny]

Yeah I'd tend towards removing them, thank you! 🙏🏻

[RubenIgnacio]

I've already remove the MoneyHelper