The length validator only takes effect for parameters with types th…

…at support `#length` method

CHANGELOG.md

@@ -3,6 +3,7 @@
 #### Features
 
 * [#2475](https://github.com/ruby-grape/grape/pull/2475): Remove Grape::Util::Registrable - [@ericproulx](https://github.com/ericproulx).
+* [#2464](https://github.com/ruby-grape/grape/pull/2464): The `length` validator only takes effect for parameters with types that support `#length` method - [@OuYangJinTing](https://github.com/OuYangJinTing).
 * Your contribution here.
 
 #### Fixes

lib/grape/validations/validators/length_validator.rb

@@ -18,7 +18,7 @@ def initialize(attrs, options, required, scope, **opts)
         def validate_param!(attr_name, params)
           param = params[attr_name]
 
-          raise ArgumentError, "parameter #{param} does not support #length" unless param.respond_to?(:length)
+          return unless param.respond_to?(:length)
 
           return unless (!@min.nil? && param.length < @min) || (!@max.nil? && param.length > @max)
 

spec/grape/validations/validators/length_spec.rb

@@ -188,11 +188,11 @@
   end
 
   describe '/type_is_not_array' do
-    context 'raises an error' do
+    context 'does not raise an error' do
       it do
         expect do
           post 'type_is_not_array', list: 12
-        end.to raise_error(ArgumentError, 'parameter 12 does not support #length')
+        end.not_to raise_error
       end
     end
   end