restrict validator.

Author: Dhruv Paranjape

README.md

@@ -1713,15 +1713,14 @@ end
 
 #### `length`
 
-Parameters can be restricted from having a specific length or size with the `:length` option.
+Parameters of type `String` or `Array` can be restricted to have a specific length or size with the `:length` option.
 
-the validator accepts `:min` or `:max` or both options to validate that they parameter is within
-the given limits.
+The validator accepts `:min` or `:max` or both options to validate that the value of the parameter is within the given limits.
 
 ```ruby
 params do
-  requires :str, length: { min: 3 }
-  requires :list, length: { min: 3, max: 5}
+  requires :str, type: String, length: { min: 3 }
+  requires :list, type: [Integer], length: { min: 3, max: 5 }
 end
 ```
 

lib/grape/validations/validators/length_validator.rb

@@ -10,14 +10,17 @@ def initialize(attrs, options, required, scope, **opts)
 
           super
 
+          raise ArgumentError, 'min must be an integer greater than or equal to zero' if !@min.nil? && (!@min.is_a?(Integer) || @min.negative?)
+          raise ArgumentError, 'max must be an integer greater than or equal to zero' if !@max.nil? && (!@max.is_a?(Integer) || @max.negative?)
           raise ArgumentError, "min #{@min} cannot be greater than max #{@max}" if !@min.nil? && !@max.nil? && @min > @max
         end
 
         def validate_param!(attr_name, params)
           param = params[attr_name]
           param = param.compact if param.respond_to?(:compact)
 
-          return unless param.respond_to?(:length)
+          raise ArgumentError, "parameter #{param} has an unsupported type. Only strings & arrays are supported" unless params.is_a?(String) || param.is_a?(Array)
+
           return unless (!@min.nil? && param.length < @min) || (!@max.nil? && param.length > @max)
 
           raise Grape::Exceptions::Validation.new(params: [@scope.full_name(attr_name)], message: build_message)

spec/grape/validations/validators/length_spec.rb

@@ -27,6 +27,36 @@
       post 'type_is_not_array' do
       end
 
+      params do
+        requires :list, type: Hash, length: { max: 3 }
+      end
+      post 'type_supports_length' do
+      end
+
+      params do
+        requires :list, type: [Integer], length: { min: -3 }
+      end
+      post 'negative_min' do
+      end
+
+      params do
+        requires :list, type: [Integer], length: { max: -3 }
+      end
+      post 'negative_max' do
+      end
+
+      params do
+        requires :list, type: [Integer], length: { min: 2.5 }
+      end
+      post 'float_min' do
+      end
+
+      params do
+        requires :list, type: [Integer], length: { max: 2.5 }
+      end
+      post 'float_max' do
+      end
+
       params do
         requires :list, type: [Integer], length: { min: 15, max: 3 }
       end
@@ -160,9 +190,51 @@
   describe '/type_is_not_array' do
     context 'is no op' do
       it do
+        expect do
         post 'type_is_not_array', list: 12
-        expect(last_response.status).to eq(201)
-        expect(last_response.body).to eq('')
+        end.to raise_error(ArgumentError, 'parameter 12 has an unsupported type. Only strings & arrays are supported')
+      end
+    end
+  end
+
+  describe '/type_supports_length' do
+    context 'raises an error' do
+      it do
+        expect do
+          post 'type_supports_length', list: { key: 'value' }
+        end.to raise_error(ArgumentError, 'parameter {"key"=>"value"} has an unsupported type. Only strings & arrays are supported')
+      end
+    end
+  end
+
+  describe '/negative_min' do
+    context 'when min is negative' do
+      it do
+        expect { post 'negative_min', list: [12] }.to raise_error(ArgumentError, 'min must be an integer greater than or equal to zero')
+      end
+    end
+  end
+
+  describe '/negative_max' do
+    context 'it raises an error' do
+      it do
+        expect { post 'negative_max', list: [12] }.to raise_error(ArgumentError, 'max must be an integer greater than or equal to zero')
+      end
+    end
+  end
+
+  describe '/float_min' do
+    context 'when min is not an integer' do
+      it do
+        expect { post 'float_min', list: [12] }.to raise_error(ArgumentError, 'min must be an integer greater than or equal to zero')
+      end
+    end
+  end
+
+  describe '/float_max' do
+    context 'when max is not an integer' do
+      it do
+        expect { post 'float_max', list: [12] }.to raise_error(ArgumentError, 'max must be an integer greater than or equal to zero')
       end
     end
   end