Ensure the value of default option must be a string when calling I18n.t

CHANGELOG.md

@@ -7,6 +7,7 @@
 #### Fixes
 
 * Your contribution here.
+* [#1737](https://github.com/ruby-grape/grape/pull/1737): Fix translating error when passing symbols as params in custom validations - [@mlzhuyi](https://github.com/mlzhuyi).
 
 ### 1.0.2 (1/10/2018)
 

lib/grape/exceptions/base.rb

@@ -71,6 +71,8 @@ def translate_message(key, **options)
       end
 
       def translate(key, **options)
+        options = options.dup
+        options[:default] &&= options[:default].to_s
         message = ::I18n.translate(key, **options)
         message.present? ? message : ::I18n.translate(key, locale: FALLBACK_LOCALE, **options)
       end

spec/grape/exceptions/validation_errors_spec.rb

@@ -43,6 +43,15 @@
         expect(subject).to contain_exactly('id is missing', 'name is missing')
       end
     end
+
+    context 'when attributes is an array of symbols' do
+      let(:validation_error) { Grape::Exceptions::Validation.new(params: [:admin_field], message: 'Can not set admin-only field') }
+      subject { described_class.new(errors: [validation_error]).full_messages }
+
+      it 'returns an array with an error full message' do
+        expect(subject.first).to eq('admin_field Can not set admin-only field')
+      end
+    end
   end
 
   context 'api' do