Allow for usage of @ConfigProperty on fields without @Inject

extensions/arc/deployment/src/main/java/io/quarkus/arc/deployment/ConfigBuildStep.java

@@ -1,16 +1,21 @@
 package io.quarkus.arc.deployment;
 
+import javax.inject.Inject;
+
 import org.eclipse.microprofile.config.Config;
 import org.eclipse.microprofile.config.ConfigProvider;
 import org.eclipse.microprofile.config.inject.ConfigProperty;
 import org.jboss.jandex.AnnotationInstance;
+import org.jboss.jandex.AnnotationTarget;
 import org.jboss.jandex.AnnotationValue;
 import org.jboss.jandex.DotName;
 import org.jboss.jandex.Type;
 
+import io.quarkus.arc.processor.AnnotationsTransformer;
 import io.quarkus.arc.processor.BeanDeploymentValidator;
 import io.quarkus.arc.processor.DotNames;
 import io.quarkus.arc.processor.InjectionPointInfo;
+import io.quarkus.deployment.annotations.BuildProducer;
 import io.quarkus.deployment.annotations.BuildStep;
 import io.smallrye.config.inject.ConfigProducer;
 
@@ -19,6 +24,8 @@
  */
 public class ConfigBuildStep {
 
+    private static final DotName CONFIG_ANNOTATION = DotName.createSimple(ConfigProperty.class.getName());
+
     @BuildStep
     AdditionalBeanBuildItem bean() {
         return new AdditionalBeanBuildItem(ConfigProducer.class.getName());
@@ -29,6 +36,31 @@ BeanDeploymentValidatorBuildItem beanDeploymentValidator() {
         return new BeanDeploymentValidatorBuildItem(new ConfigBeanDeploymentValidator());
     }
 
+    /**
+     * Uses {@link AnnotationsTransformer} to automatically add {@code @Inject} to all fields that have
+     * {@code @ConfigProperty} on them, but are missing {@code @Inject}.
+     *
+     * @author Matej Novotny
+     */
+    @BuildStep
+    public void build(BuildProducer<AnnotationsTransformerBuildItem> annotationsTransformer) throws Exception {
+        annotationsTransformer.produce(new AnnotationsTransformerBuildItem(new AnnotationsTransformer() {
+            @Override
+            public boolean appliesTo(AnnotationTarget.Kind kind) {
+                return kind == AnnotationTarget.Kind.FIELD;
+            }
+
+            @Override
+            public void transform(TransformationContext transformationContext) {
+                if (transformationContext.getTarget().asField().hasAnnotation(CONFIG_ANNOTATION)
+                        && !transformationContext.getTarget().asField().hasAnnotation(DotNames.INJECT)) {
+                    transformationContext.transform().add(Inject.class).done();
+
+                }
+            }
+        }));
+    }
+
     static class ConfigBeanDeploymentValidator implements BeanDeploymentValidator {
 
         private static final DotName CONFIG_PROPERTY_NAME = DotName.createSimple(ConfigProperty.class.getName());

extensions/arc/deployment/src/test/java/io/quarkus/arc/test/config/ConfigPropertyInjectionWithoutInjectAnnotationTest.java

@@ -0,0 +1,31 @@
+package io.quarkus.arc.test.config;
+
+import javax.inject.Inject;
+
+import org.jboss.shrinkwrap.api.ShrinkWrap;
+import org.jboss.shrinkwrap.api.asset.StringAsset;
+import org.jboss.shrinkwrap.api.spec.JavaArchive;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
+
+import io.quarkus.test.QuarkusUnitTest;
+
+public class ConfigPropertyInjectionWithoutInjectAnnotationTest {
+
+    private static final String configValue = "someValue";
+
+    @RegisterExtension
+    static final QuarkusUnitTest config = new QuarkusUnitTest()
+            .setArchiveProducer(() -> ShrinkWrap.create(JavaArchive.class)
+                    .addClasses(ConfigPropertyInjectionWithoutInjectAnnotationTest.class, SomeBeanUsingConfig.class)
+                    .addAsResource(new StringAsset("something=" + configValue), "application.properties"));
+
+    @Inject
+    SomeBeanUsingConfig bean;
+
+    @Test
+    public void testConfigWasInjected() {
+        Assertions.assertEquals(configValue, bean.getFoo());
+    }
+}

extensions/arc/deployment/src/test/java/io/quarkus/arc/test/config/SomeBeanUsingConfig.java

@@ -0,0 +1,17 @@
+package io.quarkus.arc.test.config;
+
+import javax.enterprise.context.ApplicationScoped;
+
+import org.eclipse.microprofile.config.inject.ConfigProperty;
+
+@ApplicationScoped
+public class SomeBeanUsingConfig {
+
+    // deliberately missing @Inject
+    @ConfigProperty(name = "something")
+    String foo;
+
+    public String getFoo() {
+        return foo;
+    }
+}