Added: Deprecation for env when non-string.

lib/datadog/core/configuration/settings.rb

@@ -157,7 +157,16 @@ def initialize(*_)
         # @return [String,nil]
         option :env 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 'env' configuration is deprecated. " \
+                'Use a string instead.'
+              end
+            end
+
+            v.to_s if v
+          end
 
           # NOTE: env also gets set as a side effect of tags. See the WORKAROUND note in #initialize for details.
           o.env Core::Environment::Ext::ENV_ENVIRONMENT

spec/datadog/core/configuration/settings_spec.rb

@@ -230,9 +230,8 @@
     context 'when given a symbol' do
       let(:env) { :symbol }
 
-      before { set_env }
-
-      it { expect(settings.env).to eq('symbol') }
+      it { expect { set_env }.to log_deprecation }
+      it { expect { set_env }.to change { settings.env }.from(nil).to('symbol') }
     end
 
     context 'when given `nil`' do