coerce an empty string to nil in case of the bool type

CHANGELOG.md

@@ -10,9 +10,10 @@
 
 #### Fixes
 
+* [#2049](https://github.com/ruby-grape/grape/pull/2049): Coerce an empty string to nil in case of the bool type - [@dnesteryuk](https://github.com/dnesteryuk).
 * [#2043](https://github.com/ruby-grape/grape/pull/2043): Modify declared for nested array and hash - [@kadotami](https://github.com/kadotami).
-* Your contribution here.
 * [#2040](https://github.com/ruby-grape/grape/pull/2040): Fix a regression with Array of type nil - [@ericproulx](https://github.com/ericproulx).
+* Your contribution here.
 
 ### 1.3.2 (2020/04/12)
 

lib/grape/validations/types/primitive_coercer.rb

@@ -36,7 +36,7 @@ def initialize(type, strict = false)
 
  def call(val)
  return InvalidValue.new if reject?(val)
- return nil if val.nil?
+ return nil if val.nil? || treat_as_nil?(val)
  return '' if val == ''
 
  super
@@ -46,7 +46,7 @@ def call(val)
 
  attr_reader :type
 
- # This method maintaine logic which was defined by Virtus. For example,
+ # This method maintains logic which was defined by Virtus. For example,
  # dry-types is ok to convert an array or a hash to a string, it is supported,
  # but Virtus wouldn't accept it. So, this method only exists to not introduce
  # breaking changes.
@@ -55,6 +55,13 @@ def reject?(val)
  (val.is_a?(String) && type == Hash) ||
  (val.is_a?(Hash) && type == String)
  end
+
+ # Dry-Types treats an empty string as invalid. However, Grape considers an empty string as
+ # absence of a value and coerces it into nil. See a discussion there
+ # https://github.com/ruby-grape/grape/pull/2045
+ def treat_as_nil?(val)
+ val == '' && type == Grape::API::Boolean
+ end
  end
  end
  end

spec/grape/validations/types/primitive_coercer_spec.rb

@@ -26,6 +26,10 @@
  it 'returns an error when the given value cannot be coerced' do
  expect(subject.call(123)).to be_instance_of(Grape::Validations::Types::InvalidValue)
  end
+
+ it 'coerces an empty string to nil' do
+ expect(subject.call('')).to be_nil
+ end
  end
 
  context 'String' do