Show deprecation message for relative_url_root only if used

lib/shakapacker/configuration.rb

@@ -124,12 +124,16 @@ def asset_host
   end
 
   def relative_url_root
-    Shakapacker.puts_deprecation_message "The usage of relative_url_root is deprecated in Shakapacker and will be removed in v8."
-
-    ENV.fetch(
+    result = ENV.fetch(
       "SHAKAPACKER_RELATIVE_URL_ROOT",
       fetch(:relative_url_root) || ActionController::Base.relative_url_root
     )
+
+    if result
+      Shakapacker.puts_deprecation_message("The usage of relative_url_root is deprecated in Shakapacker and will be removed in v8.")
+    end
+
+    result
   end
 
   private

spec/shakapacker/configuration_spec.rb

@@ -383,14 +383,17 @@
       )
     end
 
-    it "shows deprecation message" do
-      expect { config.relative_url_root }.to output(/deprecated/).to_stdout
-    end
-
-    it "returns the value of SHAKAPACKER_RELATIVE_URL_ROOT if set" do
-      expect(ENV).to receive(:fetch).with("SHAKAPACKER_RELATIVE_URL_ROOT", nil).and_return("custom_value")
+    context "with SHAKAPACKER_RELATIVE_URL_ROOT set" do
+      before do
+        expect(ENV).to receive(:fetch).with("SHAKAPACKER_RELATIVE_URL_ROOT", nil).and_return("custom_value")
+      end
+      it "shows deprecation message" do
+        expect { config.relative_url_root }.to output(/deprecated/).to_stdout
+      end
 
-      expect(config.relative_url_root).to eq "custom_value"
+      it "returns the value of SHAKAPACKER_RELATIVE_URL_ROOT" do
+        expect(config.relative_url_root).to eq "custom_value"
+      end
     end
 
     context "without SHAKAPACKER_RELATIVE_URL_ROOT set" do
@@ -415,6 +418,10 @@
 
             expect(config.relative_url_root).to be nil
           end
+
+          it "doesn't shows deprecation message" do
+            expect { config.relative_url_root }.to_not output(/deprecated/).to_stdout
+          end
         end
       end
     end