Added: Deprecation for service when non-string.

lib/datadog/core/configuration/settings.rb

@@ -578,7 +578,16 @@ def initialize(*_)
         # @return [String]
         option :service do |o|
           # DEV-2.0: Remove this conversion for symbol.
-          o.setter { |v| v.to_s if v }
+          o.setter do |v|
+            unless v.nil? || v.is_a?(String)
+              Datadog::Core.log_deprecation do
+                "Use of non-strings for 'service' configuration is deprecated. " \
+                'Use a string instead.'
+              end
+            end
+
+            v.to_s if v
+          end
 
           # NOTE: service also gets set as a side effect of tags. See the WORKAROUND note in #initialize for details.
           o.env Core::Environment::Ext::ENV_SERVICE

spec/datadog/core/configuration/settings_spec.rb

@@ -1041,9 +1041,8 @@
     context 'when given a symbol' do
       let(:service) { :symbol }
 
-      before { set_service }
-
-      it { expect(settings.service).to eq('symbol') }
+      it { expect { set_service }.to log_deprecation }
+      it { expect { set_service }.to change { settings.service }.to('symbol') }
     end
 
     context 'when given `nil`' do