Provide a switch to disable Spring DI bean creation

Closes: #35023

Author: geoand

extensions/spring-di/deployment/src/main/java/io/quarkus/spring/di/deployment/SpringDIProcessor.java

@@ -37,13 +37,15 @@
 import io.quarkus.deployment.Feature;
 import io.quarkus.deployment.annotations.BuildProducer;
 import io.quarkus.deployment.annotations.BuildStep;
+import io.quarkus.deployment.annotations.BuildSteps;
 import io.quarkus.deployment.builditem.FeatureBuildItem;
 
 /**
  * A simple processor that maps Spring DI annotations to CDI annotations.
  * Arc's handling of annotation mapping (by creating an extra abstraction layer on top of the Jandex index)
  * suits this sort of handling perfectly.
  */
+@BuildSteps(onlyIf = SpringDiEnabled.class)
 public class SpringDIProcessor {
 
     private static final DotName SPRING_SCOPE_ANNOTATION = DotName.createSimple("org.springframework.context.annotation.Scope");

extensions/spring-di/deployment/src/main/java/io/quarkus/spring/di/deployment/SpringDiBuildTimeConfig.java

@@ -0,0 +1,20 @@
+package io.quarkus.spring.di.deployment;
+
+import io.quarkus.runtime.annotations.ConfigPhase;
+import io.quarkus.runtime.annotations.ConfigRoot;
+import io.smallrye.config.ConfigMapping;
+import io.smallrye.config.WithDefault;
+
+@ConfigMapping(prefix = "quarkus.spring-di")
+@ConfigRoot(phase = ConfigPhase.BUILD_TIME)
+public interface SpringDiBuildTimeConfig {
+
+    /**
+     * Whether Spring DI is enabled **during the build**.
+     * <p>
+     * Turning this setting off will result in Quarkus completely ignoring beans annotated with Spring annotations
+     */
+    @WithDefault("true")
+    boolean enabled();
+
+}

extensions/spring-di/deployment/src/main/java/io/quarkus/spring/di/deployment/SpringDiEnabled.java

@@ -0,0 +1,17 @@
+package io.quarkus.spring.di.deployment;
+
+import java.util.function.BooleanSupplier;
+
+public class SpringDiEnabled implements BooleanSupplier {
+
+    private final SpringDiBuildTimeConfig config;
+
+    public SpringDiEnabled(SpringDiBuildTimeConfig config) {
+        this.config = config;
+    }
+
+    @Override
+    public boolean getAsBoolean() {
+        return config.enabled();
+    }
+}

extensions/spring-di/deployment/src/test/java/io/quarkus/spring/di/deployment/SpringDiDisabledTest.java

@@ -0,0 +1,39 @@
+package io.quarkus.spring.di.deployment;
+
+import jakarta.enterprise.inject.spi.DeploymentException;
+import jakarta.inject.Inject;
+import jakarta.inject.Singleton;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
+import org.springframework.stereotype.Component;
+
+import io.quarkus.test.QuarkusUnitTest;
+
+public class SpringDiDisabledTest {
+
+    @RegisterExtension
+    static final QuarkusUnitTest config = new QuarkusUnitTest()
+            .withApplicationRoot((jar) -> jar
+                    .addClasses(Foo.class, Bar.class))
+            .setExpectedException(DeploymentException.class)
+            .overrideConfigKey("quarkus.spring-di.enabled", "false");
+
+    @Test
+    void shouldNotBeCalled() {
+        Assertions.fail();
+    }
+
+    @Singleton
+    public static class Foo {
+
+        @Inject
+        Bar bar;
+    }
+
+    @Component
+    public static class Bar {
+
+    }
+}