Add is: parameter to the length validator

CHANGELOG.md

@@ -12,6 +12,7 @@
 * [#2478](https://github.com/ruby-grape/grape/pull/2478): Fix rescue_from with invalid response - [@ericproulx](https://github.com/ericproulx).
 * [#2480](https://github.com/ruby-grape/grape/pull/2480): Fix rescue_from ValidationErrors exception - [@numbata](https://github.com/numbata).
 * [#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).
+* [#2485](https://github.com/ruby-grape/grape/pull/2485): Add `is:` param to length validator - [@dakad](https://github.com/dakad).
 * Your contribution here.
 
 ### 2.1.3 (2024-07-13)

README.md

@@ -1714,10 +1714,11 @@ end
 
 Parameters with types that support `#length` method can be restricted to have a specific length with the `:length` option.
 
-The validator accepts `:min` or `:max` or both options to validate that the value of the parameter is within the given limits.
+The validator accepts `:min` or `:max` or both options or only `:is` to validate that the value of the parameter is within the given limits.
 
 ```ruby
 params do
+  requires :code, type: String, length: { is: 2 }
   requires :str, type: String, length: { min: 3 }
   requires :list, type: [Integer], length: { min: 3, max: 5 }
   requires :hash, type: Hash, length: { max: 5 }
@@ -2045,6 +2046,7 @@ end
 
 ```ruby
 params do
+  requires :code, type: String, length: { is: 2, message: 'code is expected to be exactly 2 characters long' }
   requires :str, type: String, length: { min: 5, message: 'str is expected to be atleast 5 characters long' }
   requires :list, type: [Integer], length: { min: 2, max: 3, message: 'list is expected to have between 2 and 3 elements' }
 end

lib/grape/locale/en.yml

@@ -11,6 +11,7 @@ en:
         except_values: 'has a value not allowed'
         same_as: 'is not the same as %{parameter}'
         length: 'is expected to have length within %{min} and %{max}'
+        length_is: 'is expected to have length exactly equal to %{is}'
         length_min: 'is expected to have length greater than or equal to %{min}'
         length_max: 'is expected to have length less than or equal to %{max}'
         missing_vendor_option:

lib/grape/validations/validators/length_validator.rb

@@ -7,20 +7,25 @@ class LengthValidator < Base
         def initialize(attrs, options, required, scope, **opts)
           @min = options[:min]
           @max = options[:max]
+          @is = options[:is]
 
           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
+
+          return if @is.nil?
+          raise ArgumentError, 'is must be an integer greater than zero' if !@is.is_a?(Integer) || !@is.positive?
+          raise ArgumentError, 'is cannot be combined with min or max' if !@min.nil? || !@max.nil?
         end
 
         def validate_param!(attr_name, params)
           param = params[attr_name]
 
           return unless param.respond_to?(:length)
 
-          return unless (!@min.nil? && param.length < @min) || (!@max.nil? && param.length > @max)
+          return unless (!@min.nil? && param.length < @min) || (!@max.nil? && param.length > @max) || (!@is.nil? && param.length != @is)
 
           raise Grape::Exceptions::Validation.new(params: [@scope.full_name(attr_name)], message: build_message)
         end
@@ -32,8 +37,10 @@ def build_message
             format I18n.t(:length, scope: 'grape.errors.messages'), min: @min, max: @max
           elsif @min
             format I18n.t(:length_min, scope: 'grape.errors.messages'), min: @min
-          else
+          elsif @max
             format I18n.t(:length_max, scope: 'grape.errors.messages'), max: @max
+          else
+            format I18n.t(:length_is, scope: 'grape.errors.messages'), is: @is
           end
         end
       end

spec/grape/validations/validators/length_spec.rb

@@ -86,6 +86,24 @@
       end
       post '/custom-message' do
       end
+
+      params do
+        requires :code, length: { is: 2 }
+      end
+      post 'is' do
+      end
+
+      params do
+        requires :code, length: { is: -2 }
+      end
+      post 'negative_is' do
+      end
+
+      params do
+        requires :code, length: { is: 2, max: 10 }
+      end
+      post 'is_with_max' do
+      end
     end
   end
 
@@ -298,4 +316,54 @@
       end
     end
   end
+
+  describe '/is' do
+    context 'when length is exact' do
+      it do
+        post 'is', code: 'ZZ'
+        expect(last_response.status).to eq(201)
+        expect(last_response.body).to eq('')
+      end
+    end
+
+    context 'when length exceeds the limit' do
+      it do
+        post 'is', code: 'aze'
+        expect(last_response.status).to eq(400)
+        expect(last_response.body).to eq('code is expected to have length exactly equal to 2')
+      end
+    end
+
+    context 'when length is less than the limit' do
+      it do
+        post 'is', code: 'a'
+        expect(last_response.status).to eq(400)
+        expect(last_response.body).to eq('code is expected to have length exactly equal to 2')
+      end
+    end
+
+    context 'when length is zero' do
+      it do
+        post 'is', code: ''
+        expect(last_response.status).to eq(400)
+        expect(last_response.body).to eq('code is expected to have length exactly equal to 2')
+      end
+    end
+  end
+
+  describe '/negative_is' do
+    context 'when `is` is negative' do
+      it do
+        expect { post 'negative_is', code: 'ZZ' }.to raise_error(ArgumentError, 'is must be an integer greater than zero')
+      end
+    end
+  end
+
+  describe '/is_with_max' do
+    context 'when `is` is combined with max' do
+      it do
+        expect { post 'is_with_max', code: 'ZZ' }.to raise_error(ArgumentError, 'is cannot be combined with min or max')
+      end
+    end
+  end
 end