do not raise an IncompatibleOptionValues For a couple of potentially valid use cases

CHANGELOG.md

@@ -8,6 +8,7 @@
 * [#1237](/~https://github.com/ruby-grape/grape/pull/1237): Allow multiple parameters in `given`, which behaves as if the scopes were nested in the inputted order - [@ochagata](/~https://github.com/ochagata).
 * [#1238](/~https://github.com/ruby-grape/grape/pull/1238): Call `after` of middleware on error - [@namusyaka](/~https://github.com/namusyaka).
 * [#1243](/~https://github.com/ruby-grape/grape/pull/1243): Add `header` support for middleware - [@namusyaka](/~https://github.com/namusyaka).
+* [#1252](/~https://github.com/ruby-grape/grape/pull/1252): Allow default to be a subset or equal to allowed values without raising IncompatibleOptionValues - [@jeradphelps](/~https://github.com/jeradphelps).
 * Your contribution here.
 
 #### Fixes

lib/grape/validations/params_scope.rb

@@ -316,7 +316,7 @@ def guess_coerce_type(coerce_type, values)
       def check_incompatible_option_values(values, default)
         return unless values && default
         return if values.is_a?(Proc) || default.is_a?(Proc)
-        return if values.include?(default)
+        return if values.include?(default) || (Array(default) - Array(values)).empty?
         fail Grape::Exceptions::IncompatibleOptionValues.new(:default, default, :values, values)
       end
 

spec/grape/validations/params_scope_spec.rb

@@ -174,6 +174,24 @@ def initialize(value)
       end
     end
 
+    context 'when the default is an array' do
+      context 'and is the entire range of allowed values' do
+        it 'does not raise an exception' do
+          expect do
+            subject.params { optional :numbers, type: Array[Integer], values: 0..2, default: 0..2 }
+          end.to_not raise_error
+        end
+      end
+
+      context 'and is a subset of allowed values' do
+        it 'does not raise an exception' do
+          expect do
+            subject.params { optional :numbers, type: Array[Integer], values: [0, 1, 2], default: [1, 0] }
+          end.to_not raise_error
+        end
+      end
+    end
+
     context 'when both range endpoints are #kind_of? the type' do
       it 'accepts values in the range' do
         subject.params do