Allow "if: Proc..." on link

lib/fast_jsonapi/attribute.rb

@@ -1,29 +1,5 @@
-module FastJsonapi
-  class Attribute
-    attr_reader :key, :method, :conditional_proc
-
-    def initialize(key:, method:, options: {})
-      @key = key
-      @method = method
-      @conditional_proc = options[:if]
-    end
+require 'fast_jsonapi/scalar'
 
-    def serialize(record, serialization_params, output_hash)
-      if include_attribute?(record, serialization_params)
-        output_hash[key] = if method.is_a?(Proc)
-          method.arity.abs == 1 ? method.call(record) : method.call(record, serialization_params)
-        else
-          record.public_send(method)
-        end
-      end
-    end
-
-    def include_attribute?(record, serialization_params)
-      if conditional_proc.present?
-        conditional_proc.call(record, serialization_params)
-      else
-        true
-      end
-    end
-  end
+module FastJsonapi
+  class Attribute < Scalar; end
 end

lib/fast_jsonapi/link.rb

@@ -1,18 +1,5 @@
-module FastJsonapi
-  class Link
-    attr_reader :key, :method
-
-    def initialize(key:, method:)
-      @key = key
-      @method = method
-    end
+require 'fast_jsonapi/scalar'
 
-    def serialize(record, serialization_params, output_hash)
-      output_hash[key] = if method.is_a?(Proc)
-        method.arity == 1 ? method.call(record) : method.call(record, serialization_params)
-      else
-        record.public_send(method)
-      end
-    end
-  end
+module FastJsonapi
+  class Link < Scalar; end
 end

lib/fast_jsonapi/object_serializer.rb

@@ -285,14 +285,19 @@ def fetch_polymorphic_option(options)
         {}
       end
 
-      def link(link_name, link_method_name = nil, &block)
+      # def link(link_name, link_method_name = nil, &block)
+      def link(*params, &block)
         self.data_links = {} if self.data_links.nil?
-        link_method_name = link_name if link_method_name.nil?
+
+        options = params.last.is_a?(Hash) ? params.pop : {}
+        link_name = params.first
+        link_method_name = params[-1]
         key = run_key_transform(link_name)
 
         self.data_links[key] = Link.new(
           key: key,
-          method: block || link_method_name
+          method: block || link_method_name,
+          options: options
         )
       end
 

lib/fast_jsonapi/scalar.rb

@@ -0,0 +1,29 @@
+module FastJsonapi
+  class Scalar
+    attr_reader :key, :method, :conditional_proc
+
+    def initialize(key:, method:, options: {})
+      @key = key
+      @method = method
+      @conditional_proc = options[:if]
+    end
+
+    def serialize(record, serialization_params, output_hash)
+      if conditionally_allowed?(record, serialization_params)
+        output_hash[key] = if method.is_a?(Proc)
+          method.arity.abs == 1 ? method.call(record) : method.call(record, serialization_params)
+        else
+          record.public_send(method)
+        end
+      end
+    end
+
+    def conditionally_allowed?(record, serialization_params)
+      if conditional_proc.present?
+        conditional_proc.call(record, serialization_params)
+      else
+        true
+      end
+    end
+  end
+end

spec/lib/object_serializer_class_methods_spec.rb

@@ -400,6 +400,26 @@ def year_since_release_calculator(release_year)
         expect(action_serializable_hash[:data][:links][:url]).to eq "/action-movie/#{movie.id}"
       end
     end
+
+    describe 'optional links' do
+      subject(:downloadable_serializable_hash) { OptionalDownloadableMovieSerializer.new(movie, params).serializable_hash }
+
+      context 'when the link is provided' do
+        let(:params) { { params: { signed_url: signed_url } } }
+        let(:signed_url) { 'http://example.com/download_link?signature=abcdef' }
+
+        it 'includes the link' do
+          expect(downloadable_serializable_hash[:data][:links][:download]).to eq signed_url
+        end
+      end
+
+      context 'when the link is not provided' do
+        let(:params) { { params: {} } }
+        it 'does not include the link' do
+          expect(downloadable_serializable_hash[:data][:links]).to_not have_key(:download)
+        end
+      end
+    end
   end
 
   describe '#key_transform' do

spec/shared/contexts/movie_context.rb

@@ -197,6 +197,12 @@ class HorrorMovieSerializer < GenreMovieSerializer
       link(:url) { |object| "/horror-movie/#{object.id}" }
     end
 
+    class OptionalDownloadableMovieSerializer < MovieSerializer
+      link(:download, if: Proc.new { |record, params| params && params[:signed_url] }) do |movie, params|
+        params[:signed_url]
+      end
+    end
+
     class MovieWithoutIdStructSerializer
       include FastJsonapi::ObjectSerializer
       attributes :name, :release_year
@@ -385,6 +391,7 @@ class MovieSerializer
       ActionMovieSerializer
       GenreMovieSerializer
       HorrorMovieSerializer
+      OptionalDownloadableMovieSerializer
       Movie
       MovieSerializer
       Actor