Indifference to I18n errors.format translation

[Mekajiki]

Problem

When errors.format translation is defined differently than %{attribute} %{message}, a test using validate_presence_of
matcher with strict seems not to be proved.

Example

If the translations are defined as;

  errors: 
    format: "%{attribute}%{message}"
    messages: 
      blank: を入力してください

And if you write a test as below;

class A
  incude ActiveModel::Model
  include ActiveModel::Validations

  attr_accessor :value
  
  validates :value, presence: true, strict: true
end

class MenuItemTest < ActiveSupport::TestCase
  subject { A.new }
  
  context "Validations" do
    should validate_presence_of(:value).strict
  end
end

The test above isn't proved with message like;

  After setting :value to ‹nil›, the matcher expected the
  A to be invalid and to raise a validation
  exception with message "Value を入力してください". The record was indeed
  invalid, but the exception message was "Valueを入力してください"
  instead.

The matcher seems to expect a space exists between attribute name and message, but actually doesn't.

Possible Solution

Taking errors.format definition into account might be a good solution.
Seeing how Ruby on Rails raise exceptions, it uses errors.format to compose attribute name and message into a string.
https://github.com/rails/rails/blob/4bbd05c90e5a62c0316307b3ca7c2262ed98b567/activemodel/lib/active_model/errors.rb#L290-L294

      I18n.t(:"errors.format", {
        :default   => "%{attribute} %{message}",
        :attribute => attr_name,
        :message   => message
      })

But validation matcher seems to check messages with fixed format.

shoulda-matchers/lib/shoulda/matchers/active_model/allow_value_matcher.rb

Line 615 in 206d2da

"#{human_attribute_name} #{default_attribute_message}"

Changing this code into the same manner as in RoR may solve the problem.