Allow thumbnail_field config to take an array of possible fields

app/presenters/blacklight/thumbnail_presenter.rb

@@ -28,16 +28,16 @@ def exists?
     # @param [Hash] image_options to pass to the image tag
     # @param [Hash] url_options to pass to #link_to_document
     # @return [String]
-    # rubocop:disable Lint/AssignmentInCondition
     def thumbnail_tag image_options = {}, url_options = {}
-      return unless value = thumbnail_value(image_options)
+      value = thumbnail_value(image_options)
+      return unless value
+
       if url_options == false || url_options[:suppress_link]
         value
       else
         view_context.link_to_document document, value, url_options
       end
     end
-    # rubocop:enable Lint/AssignmentInCondition
 
     private
 
@@ -48,8 +48,8 @@ def thumbnail_value(image_options)
       if thumbnail_method
         view_context.send(thumbnail_method, document, image_options)
       elsif thumbnail_field
-        url = document.first(thumbnail_field)
-        view_context.image_tag url, image_options if url.present?
+        image_url = Array(thumbnail_field).lazy.map { |field| document.first(field) }.reject(&:blank?).first
+        view_context.image_tag image_url, image_options if image_url.present?
       end
     end
   end

spec/presenters/thumbnail_presenter_spec.rb

@@ -17,7 +17,7 @@
       it { is_expected.to be true }
     end
 
-    context "when thumbnail_field is configured" do
+    context "when thumbnail_field is configured as a single field" do
       let(:config) do
         Blacklight::OpenStructWithHashAccess.new(thumbnail_field: :xyz)
       end
@@ -33,6 +33,18 @@
       end
     end
 
+    context "when thumbnail_field is configured as an array of fields" do
+      let(:config) do
+        Blacklight::OpenStructWithHashAccess.new(thumbnail_field: [:rst, :uvw, :xyz])
+      end
+
+      context "and the field exists in the document" do
+        let(:document) { SolrDocument.new('xyz' => 'image.png') }
+
+        it { is_expected.to be true }
+      end
+    end
+
     context "without any configured options" do
       it { is_expected.to be_falsey }
     end
@@ -88,7 +100,6 @@
       end
 
       it "creates an image tag from the given field" do
-        #allow(document).to receive(:has?).with(:xyz).and_return(true)
         allow(document).to receive(:first).with(:xyz).and_return("http://example.com/some.jpg")
         allow(view_context).to receive(:image_tag).with("http://example.com/some.jpg", {}).and_return('<img src="image.jpg">')
         expect(view_context).to receive(:link_to_document).with(document, '<img src="image.jpg">', {})
@@ -101,6 +112,22 @@
       end
     end
 
+    context "when thumbnail_field is configured as an array of fields" do
+      let(:config) do
+        Blacklight::OpenStructWithHashAccess.new(thumbnail_field: [:rst, :uvw, :xyz])
+      end
+
+      context "and the field exists in the document" do
+        let(:document) { SolrDocument.new(xyz: 'http://example.com/some.jpg') }
+
+        it "creates an image tag from the given field" do
+          allow(view_context).to receive(:image_tag).with("http://example.com/some.jpg", {}).and_return('<img src="image.jpg">')
+          expect(view_context).to receive(:link_to_document).with(document, '<img src="image.jpg">', {}).and_return('<a><img></a>')
+          expect(presenter.thumbnail_tag).to eq '<a><img></a>'
+        end
+      end
+    end
+
     context "when no thumbnail is configured" do
       it { is_expected.to be_nil }
     end