Allow defining attributes on SolrDocument

app/models/concerns/blacklight/document.rb

@@ -116,5 +116,21 @@ module ClassMethods
     def unique_key
       @unique_key ||= 'id'
     end
+
+    # Define an attribute reader on a document model
+    # @Example
+    #   class SolrDocument
+    #     include Blacklight::Solr::Document
+    #     attribute :title, Blacklight::Types::String, 'title_tesim'
+    #   end
+    #
+    #   doc = SolrDocument.new(title_tesim: ["One flew over the cuckoo's nest"])
+    #   doc.title
+    #   #=> "One flew over the cuckoo's nest"
+    def attribute(name, type, field)
+      define_method name do
+        type.coerce(self[field])
+      end
+    end
   end
 end

app/values/blacklight/types.rb

@@ -0,0 +1,28 @@
+module Blacklight
+  # These are data types that blacklight can use to coerce values from the index
+  module Types
+    class Array
+      def self.coerce(input)
+        ::Array.wrap(input)
+      end
+    end
+
+    class String
+      def self.coerce(input)
+        ::Array.wrap(input).first
+      end
+    end
+
+    class Date
+      def self.coerce(input)
+        field = String.coerce(input)
+        return if field.blank?
+        begin
+          ::Date.parse(field)
+        rescue ArgumentError
+          Rails.logger.info "Unable to parse date: #{field.first.inspect}"
+        end
+      end
+    end
+  end
+end

spec/models/solr_document_spec.rb

@@ -1,31 +1,54 @@
 # frozen_string_literal: true
 
 describe SolrDocument do
-  
+
   before(:each) do
-    
+
     @solrdoc = SolrDocument.new :id => '00282214', :format => ['Book'], :title_display => 'some-title'
 
   end
-  
+
   describe "new" do
     it "takes a Hash as the argument" do
       expect { SolrDocument.new(:id => 1) }.not_to raise_error
     end
   end
-  
+
   describe "access methods" do
 
     it "has the right value for title_display" do
       expect(@solrdoc[:title_display]).not_to be_nil
     end
-    
+
     it "has the right value for format" do
       expect(@solrdoc[:format][0]).to eq 'Book'
     end
-    
+
     it "provides the item's solr id" do
       expect(@solrdoc.id).to eq '00282214'
     end
   end
-end
+
+  describe '.attribute' do
+    subject(:title) { document.title }
+    let(:doc_class) do
+      Class.new(SolrDocument) do
+        attribute :title, Blacklight::Types::String, 'title_tesim'
+        attribute :author, Blacklight::Types::Array, 'author_tesim'
+        attribute :date, Blacklight::Types::Date, 'date_dtsi'
+
+      end
+    end
+    let(:document) do
+      doc_class.new(id: '123',
+                    title_tesim: ['Good Omens'],
+                    author_tesim: ['Neil Gaiman', 'Terry Pratchett'],
+                    date_dtsi: '1990-01-01T00:00:00Z')
+    end
+    it "casts the attributes" do
+      expect(document.title).to eq 'Good Omens'
+      expect(document.author).to eq ['Neil Gaiman', 'Terry Pratchett']
+      expect(document.date).to eq Date.new(1990)
+    end
+  end
+end