Handle length validator with procs

Devise changed their password validations to use a proc for
minimum/maximum for additional customization, but that apparently broke
SimpleForm minlength/maxlength logic since it wasn't handling that.

Instead of implementing it custom by checking for the value responding
to `call` like we do for a couple of other validators, I went with the
route of copying over the `resolve_value` implementation added to Rails
7.1 that handles all the possible scenarios for procs / send / etc,
which allows different ways of setting up the proc.

Closes #1858

Author: carlosantoniodasilva

lib/simple_form/components/maxlength.rb

@@ -26,7 +26,8 @@ def find_length_validator
 
       def maximum_length_value_from(length_validator)
         if length_validator
-          length_validator.options[:is] || length_validator.options[:maximum]
+          value = length_validator.options[:is] || length_validator.options[:maximum]
+          resolve_validator_value(value)
         end
       end
     end

lib/simple_form/components/minlength.rb

@@ -26,7 +26,8 @@ def find_length_validator
 
       def minimum_length_value_from(length_validator)
         if length_validator
-          length_validator.options[:is] || length_validator.options[:minimum]
+          value = length_validator.options[:is] || length_validator.options[:minimum]
+          resolve_validator_value(value)
         end
       end
     end

lib/simple_form/helpers/validators.rb

@@ -40,6 +40,27 @@ def action_validator_match?(validator)
       def find_validator(kind)
         attribute_validators.find { |v| v.kind == kind } if has_validators?
       end
+
+      # Implements `ActiveModel::Validations::ResolveValue`, introduced by Rails 7.1.
+      # https://github.com/rails/rails/blob/v7.1.0/activemodel/lib/active_model/validations/resolve_value.rb
+      def resolve_validator_value(value)
+        case value
+        when Proc
+          if value.arity == 0
+            value.call
+          else
+            value.call(object)
+          end
+        when Symbol
+          object.send(value)
+        else
+          if value.respond_to?(:call)
+            value.call(object)
+          else
+            value
+          end
+        end
+      end
     end
   end
 end

test/inputs/string_input_test.rb

@@ -33,16 +33,26 @@ class StringInputTest < ActionView::TestCase
     assert_select 'input.password[type=password][maxlength="100"]'
   end
 
-  test 'input infers maxlength column definition from validation when present' do
+  test 'input infers maxlength from validation when present' do
     with_input_for @validating_user, :name, :string
     assert_select 'input.string[maxlength="25"]'
   end
 
-  test 'input infers minlength column definition from validation when present' do
+  test 'input infers minlength from validation when present' do
     with_input_for @validating_user, :name, :string
     assert_select 'input.string[minlength="5"]'
   end
 
+  test 'input infers maxlength from validation proc when present' do
+    with_input_for @validating_user, :username, :string
+    assert_select 'input.string[maxlength="30"]'
+  end
+
+  test 'input infers minlength from validation proc when present' do
+    with_input_for @validating_user, :username, :string
+    assert_select 'input.string[minlength="10"]'
+  end
+
   test 'input gets maxlength from validation when :is option present' do
     with_input_for @validating_user, :home_picture, :string
     assert_select 'input.string[maxlength="12"]'

test/support/models.rb

@@ -88,7 +88,7 @@ class User
   extend ActiveModel::Naming
   include ActiveModel::Conversion
 
-  attr_accessor :id, :name, :company, :company_id, :time_zone, :active, :age,
+  attr_accessor :id, :name, :username, :company, :company_id, :time_zone, :active, :age,
     :description, :created_at, :updated_at, :credit_limit, :password, :url,
     :delivery_time, :born_at, :special_company_id, :country, :tags, :tag_ids,
     :avatar, :home_picture, :email, :status, :residence_country, :phone_number,
@@ -261,6 +261,7 @@ def self.readonly_attributes
 class ValidatingUser < User
   include ActiveModel::Validations
   validates :name, presence: true
+  validates :username, presence: true
   validates :company, presence: true
   validates :age, presence: true, if: proc { |user| user.name }
   validates :amount, presence: true, unless: proc { |user| user.age }
@@ -282,6 +283,7 @@ class ValidatingUser < User
     less_than_or_equal_to: :max_attempts,
     only_integer: true
   validates_length_of :name, maximum: 25, minimum: 5
+  validates_length_of :username, maximum: -> { 30 }, minimum: -> { 10 }
   validates_length_of :description, in: 15..50
   validates_length_of :home_picture, is: 12
 

test/test_helper.rb

@@ -56,6 +56,7 @@ def setup_users(extra_attributes = {})
 
     @validating_user = ValidatingUser.build({
       name: 'Tester McTesterson',
+      username: 'mctesterson',
       description: 'A test user of the most distinguished caliber',
       home_picture: 'Home picture',
       age: 19,