4.x: Fix wrong method generated for factory methods in builder (helidon-io#10522)

* Config factory methods for types that are also configured blueprints no longer generate an invalid method if the return type is a list.
Added tests

Author: tomas-langer

builder/codegen/src/main/java/io/helidon/builder/codegen/TypeHandlerCollection.java

@@ -344,6 +344,11 @@ private void factorySetterConsumer(InnerClass.Builder classBuilder,
                                        Javadoc blueprintJavadoc,
                                        FactoryMethods factoryMethods,
                                        FactoryMethods.FactoryMethod factoryMethod) {
+        if (!configured.singular()) {
+            // if singular is not defined, we are not instructed to create add methods, so it does not make sense
+            // to create an add method with a builder consumer
+            return;
+        }
         // if there is a factory method for the return type, we also have setters for the type (probably config object)
         TypeName builderType;
         if (factoryMethod.factoryMethodReturnType().className().equals("Builder")) {
@@ -382,14 +387,20 @@ private void factorySetterConsumer(InnerClass.Builder classBuilder,
             builder.addContentLine("this." + name() + "(builder.build());")
                     .addContentLine("return self();");
             classBuilder.addMethod(builder);
-        } else if (configured.singular()) {
-            String singularName = configured.singularName();
-            String methodName = "add" + capitalize(singularName);
-            builder.name(methodName)
-                    .addContentLine("this." + name() + ".add(builder.build());")
-                    .addContentLine("return self();");
-            classBuilder.addMethod(builder);
+            return;
+        }
+
+        String singularName = configured.singularName();
+        String methodName;
+        if (configured.singularAddPrefix()) {
+            methodName = "add" + capitalize(singularName);
+        } else {
+            methodName = singularName;
         }
+        builder.name(methodName)
+                .addContentLine("this." + name() + ".add(builder.build());")
+                .addContentLine("return self();");
+        classBuilder.addMethod(builder);
     }
 
     private void singularSetter(InnerClass.Builder classBuilder,

builder/tests/builder/src/main/java/io/helidon/builder/test/testsubjects/OtelTracingBlueprint.java

@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2025 Oracle and/or its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.helidon.builder.test.testsubjects;
+
+import java.util.List;
+
+import io.helidon.builder.api.Option;
+import io.helidon.builder.api.Prototype;
+
+@Prototype.Configured
+@Prototype.Blueprint
+@Prototype.CustomMethods(OtelTracingSupport.class)
+interface OtelTracingBlueprint {
+    @Option.Configured
+    List<SpanProcessorConfig> processors();
+}

builder/tests/builder/src/main/java/io/helidon/builder/test/testsubjects/OtelTracingSupport.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2025 Oracle and/or its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.helidon.builder.test.testsubjects;
+
+import java.util.List;
+
+import io.helidon.builder.api.Prototype;
+import io.helidon.common.config.Config;
+
+final class OtelTracingSupport {
+    private OtelTracingSupport() {
+    }
+
+    @Prototype.FactoryMethod
+    static List<SpanProcessorConfig> createProcessors(Config config) {
+        return List.of(SpanProcessorConfig.builder()
+                               .configured("some-value")
+                               .build());
+    }
+}

builder/tests/builder/src/main/java/io/helidon/builder/test/testsubjects/SpanProcessorConfigBlueprint.java

@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) 2025 Oracle and/or its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.helidon.builder.test.testsubjects;
+
+import io.helidon.builder.api.Option;
+import io.helidon.builder.api.Prototype;
+
+@Prototype.Blueprint
+@Prototype.Configured
+interface SpanProcessorConfigBlueprint {
+    @Option.Configured
+    String configured();
+}

builder/tests/builder/src/test/java/io/helidon/builder/test/TestFactoryMethod.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2025 Oracle and/or its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.helidon.builder.test;
+
+import java.util.Map;
+
+import io.helidon.builder.test.testsubjects.OtelTracing;
+import io.helidon.config.Config;
+import io.helidon.config.ConfigSources;
+
+import org.junit.jupiter.api.Test;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.collection.IsCollectionWithSize.hasSize;
+
+class TestFactoryMethod {
+     @Test
+    void testConfigFactory() {
+        var config = Config.just(ConfigSources.create(Map.of("processors", "")));
+
+        var otelConfig = OtelTracing.create(config);
+        var processors = otelConfig.processors();
+
+        assertThat(processors, hasSize(1));
+        // returned from here: io.helidon.builder.test.testsubjects.OtelTracingSupport.createProcessors
+        assertThat(processors.getFirst().configured(), is("some-value"));
+    }
+}