Add optimistic_lock_token to valkyrie resources on query

lib/valkyrie/persistence/solr/orm_converter.rb

@@ -24,7 +24,7 @@ def internal_resource
     end
 
     def attributes
-      attribute_hash.merge("id" => id, internal_resource: internal_resource, created_at: created_at, updated_at: updated_at)
+      attribute_hash.merge("id" => id, internal_resource: internal_resource, created_at: created_at, updated_at: updated_at, optimistic_lock_token: version)
     end
 
     def created_at
@@ -35,6 +35,10 @@ def updated_at
       DateTime.parse(solr_document["timestamp"] || solr_document.fetch("created_at_dtsi").to_s).utc
     end
 
+    def version
+      solr_document.fetch('_version_', nil)
+    end
+
     def id
       solr_document.fetch('id').sub(/^id-/, '')
     end

lib/valkyrie/specs/shared_specs/locking_query.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+RSpec.shared_examples 'a Valkyrie locking query provider' do
+  before do
+    raise 'adapter must be set with `let(:adapter)`' unless
+      defined? adapter
+    class CustomLockingQueryResource < Valkyrie::Resource
+      enable_optimistic_locking
+      attribute :id, Valkyrie::Types::ID.optional
+      attribute :title
+    end
+  end
+  after do
+    Object.send(:remove_const, :CustomLockingQueryResource)
+  end
+
+  let(:query_service) { adapter.query_service } unless defined? query_service
+  let(:persister) { adapter.persister }
+  subject { adapter.query_service }
+
+  it "retrieves the lock token and casts it to optimistic_lock_token attribute" do
+    resource = CustomLockingQueryResource.new(title: "My Title")
+    resource = persister.save(resource: resource)
+    resource = query_service.find_by(id: resource.id)
+    # we can't know the value in the general case
+    expect(resource.optimistic_lock_token).not_to be_empty
+  end
+end

spec/valkyrie/persistence/solr/query_service_spec.rb

@@ -1,14 +1,41 @@
 # frozen_string_literal: true
 require 'spec_helper'
 require 'valkyrie/specs/shared_specs'
+require 'valkyrie/specs/shared_specs/locking_query'
 
 RSpec.describe Valkyrie::Persistence::Solr::QueryService do
   before do
     client = RSolr.connect(url: SOLR_TEST_URL)
     client.delete_by_query("*:*")
     client.commit
   end
+
   let(:adapter) { Valkyrie::Persistence::Solr::MetadataAdapter.new(connection: client) }
   let(:client) { RSolr.connect(url: SOLR_TEST_URL) }
   it_behaves_like "a Valkyrie query provider"
+  it_behaves_like "a Valkyrie locking query provider"
+
+  describe "optimistic locking" do
+    let(:query_service) { adapter.query_service } unless defined? query_service
+    let(:persister) { adapter.persister }
+
+    before do
+      class CustomLockingResource < Valkyrie::Resource
+        enable_optimistic_locking
+        attribute :id, Valkyrie::Types::ID.optional
+        attribute :title
+      end
+    end
+
+    after do
+      Object.send(:remove_const, :CustomLockingResource)
+    end
+
+    it "retrieves the lock token and casts it to optimistic_lock_token attribute" do
+      resource = persister.save(resource: CustomLockingResource.new(title: "My Title"))
+      resource = query_service.find_by(id: resource.id)
+      query_doc = (query_service.connection.get 'select', params: { q: "id:#{resource.id}" })["response"]["docs"].first
+      expect(resource.optimistic_lock_token.first).to eq query_doc["_version_"]
+    end
+  end
 end