Filter instead of failing for nil string values

This currently fails with

`Unsupported argument type: NilClass. Construct an Arel node instead.`

when the scope is resolved.

Prior art from #410

Author: amaierhofer

lib/graphiti/adapters/active_record.rb

@@ -41,22 +41,24 @@ def filter_not_eq(scope, attribute, value)
       alias_method :filter_enum_not_eql, :filter_not_eq
 
       def filter_string_eq(scope, attribute, value, is_not: false)
+        return filter_string_eql(scope, attribute, nil, is_not: is_not) if Array(value).compact.blank?
+
         column = column_for(scope, attribute)
-        clause = column.lower.eq_any(value.map(&:downcase))
+        clause = column.lower.eq_any(value.map { |val| val.downcase })
         is_not ? scope.where.not(clause) : scope.where(clause)
       end
 
       def filter_string_eql(scope, attribute, value, is_not: false)
-        clause = {attribute => value}
+        clause = {attribute => value.presence}
         is_not ? scope.where.not(clause) : scope.where(clause)
       end
 
       def filter_string_not_eq(scope, attribute, value)
-        filter_string_eq(scope, attribute, value, is_not: true)
+        filter_string_eq(scope, attribute, value.presence, is_not: true)
       end
 
       def filter_string_not_eql(scope, attribute, value)
-        filter_string_eql(scope, attribute, value, is_not: true)
+        filter_string_eql(scope, attribute, value.presence, is_not: true)
       end
 
       # Arel has different match escaping behavior before rails 5.

spec/integration/rails/finders_spec.rb

@@ -281,6 +281,15 @@ def resource
           it "executes case-insensitive search" do
             expect(ids).to eq([author2.id, author3.id])
           end
+
+          context "with nil value" do
+            let(:value) { nil }
+            let!(:author3) { Legacy::Author.create! }
+
+            it "works" do
+              expect(ids).to eq([author3.id])
+            end
+          end
         end
 
         context "nothing" do
@@ -297,6 +306,15 @@ def resource
           it "executes case-sensitive search" do
             expect(ids).to eq([author3.id])
           end
+
+          context "with nil value" do
+            let(:value) { nil }
+            let!(:author3) { Legacy::Author.create! }
+
+            it "works" do
+              expect(ids).to eq([author3.id])
+            end
+          end
         end
 
         context "!eq" do
@@ -305,6 +323,15 @@ def resource
           it "executes case-insensitive NOT search" do
             expect(ids).to eq([author1.id])
           end
+
+          context "with nil value" do
+            let(:value) { {'!eq': nil} }
+            let!(:author3) { Legacy::Author.create! }
+
+            it "works" do
+              expect(ids).to eq([author1.id, author2.id])
+            end
+          end
         end
 
         # test not_ alternative to !
@@ -314,6 +341,15 @@ def resource
           it "executes case-insensitive NOT search" do
             expect(ids).to eq([author1.id])
           end
+
+          context "with nil value" do
+            let(:value) { {not_eq: nil} }
+            let!(:author3) { Legacy::Author.create! }
+
+            it "works" do
+              expect(ids).to eq([author1.id, author2.id])
+            end
+          end
         end
 
         # test not_ alternative to !

spec/tmp/local_secret.txt

@@ -0,0 +1 @@
+85b70ecb76ac772627f629a92a3b6f480e5ef6f12d4ba704656d87a8e9c2c2bad3155ea4fab11f4837d94dba3436c9c31bd9468f0603a4c9f0aa28641ac6a5d5