Typecast certain string filters automatically

* `"true" becomes `true`
* `"false" becomes `false`
* `"nil" becomes `nil`
* `"null" becomes `nil`

Author: Lee Richmond

lib/jsonapi_compliable/scoping/filter.rb

@@ -52,8 +52,31 @@ def each_filter
         filter = find_filter!(param_name.to_sym)
         value  = param_value
         value  = value.split(',') if value.is_a?(String) && value.include?(',')
+        value  = normalize_string_values(value)
         yield filter, value
       end
     end
+
+    # Convert a string of "true" to true, etc
+    #
+    # NB - avoid Array(value) here since we might want to
+    # return a single element instead of array
+    def normalize_string_values(value)
+      if value.is_a?(Array)
+        value.map { |v| normalize_string_value(v) }
+      else
+        normalize_string_value(value)
+      end
+    end
+
+    def normalize_string_value(value)
+      case value
+      when 'true' then true
+      when 'false' then false
+      when 'nil', 'null' then nil
+      else
+        value
+      end
+    end
   end
 end

spec/filtering_spec.rb

@@ -13,6 +13,7 @@
       allow_filter :first_name_prefix do |scope, value|
         scope.where(['first_name like ?', "#{value}%"])
       end
+      allow_filter :active
     end
   end
 
@@ -26,6 +27,54 @@
     expect(scope.resolve.map(&:id)).to eq([author1.id])
   end
 
+  context 'when filter is a "string nil"' do
+    before do
+      params[:filter] = { first_name: 'nil' }
+      author2.update_attribute(:first_name, nil)
+    end
+
+    it 'converts to a real nil' do
+      ids = scope.resolve.map(&:id)
+      expect(ids).to eq([author2.id])
+    end
+  end
+
+  context 'when filter is a "string null"' do
+    before do
+      params[:filter] = { first_name: 'null' }
+      author2.update_attribute(:first_name, nil)
+    end
+
+    it 'converts to a real nil' do
+      ids = scope.resolve.map(&:id)
+      expect(ids).to eq([author2.id])
+    end
+  end
+
+  context 'when filter is a "string boolean"' do
+    before do
+      params[:filter] = { active: 'true' }
+      author2.update_attribute(:active, false)
+    end
+
+    it 'automatically casts to a real boolean' do
+      ids = scope.resolve.map(&:id)
+      expect(ids.length).to eq(3)
+      expect(ids).to_not include(author2.id)
+    end
+
+    context 'and multiple are passed' do
+      before do
+        params[:filter] = { active: 'true,false' }
+      end
+
+      it 'still works' do
+        ids = scope.resolve.map(&:id)
+        expect(ids.length).to eq(4)
+      end
+    end
+  end
+
   context 'when filter is an integer' do
     before do
       params[:filter] = { id: author1.id }

spec/fixtures/legacy.rb

@@ -1,5 +1,6 @@
 ActiveRecord::Schema.define(:version => 1) do
   create_table :authors do |t|
+    t.boolean :active, default: true
     t.string :first_name
     t.string :last_name
     t.string :dwelling_type