Incorporate review comments

* Use a constant for sharing data between the two processes
* Raise an exception if the mapping data is invalid.
* Include a functional-test for verifying the plugin behavior

devtools/gradle/build.gradle

@@ -27,6 +27,17 @@ repositories {
     mavenCentral()
 }
 
+sourceSets {
+    // Functional Tests
+    funcTest {
+        java.srcDir 'src/funcTest/java'
+        resources.srcDir 'src/funcTest/resources'
+
+        compileClasspath += sourceSets.main.output + configurations.testRuntimeClasspath + configurations.compileOnly
+        runtimeClasspath += output + compileClasspath
+    }
+}
+
 configurations.all {
     exclude group: 'io.quarkus', module: 'quarkus-bootstrap-maven-resolver'
 }
@@ -64,9 +75,9 @@ javadoc {
 }
 
 pluginBundle {
-    website = 'https://quarkus.io/' 
-    vcsUrl = 'https://github.com/quarkusio/quarkus' 
-    tags = ['quarkus', 'quarkusio', 'graalvm'] 
+    website = 'https://quarkus.io/'
+    vcsUrl = 'https://github.com/quarkusio/quarkus'
+    tags = ['quarkus', 'quarkusio', 'graalvm']
 }
 
 gradlePlugin {
@@ -83,3 +94,29 @@ gradlePlugin {
 wrapper {
     distributionType = Wrapper.DistributionType.ALL
 }
+
+/*
+ * Functional tests for this module.
+ */
+task functionalTest(type: Test, description: 'Functional tests', dependsOn: [processResources, classes]) {
+    description = 'Run the functional tests.'
+    group = 'verification'
+
+    useJUnitPlatform()
+    testClassesDirs = sourceSets.funcTest.output.classesDirs
+    classpath = sourceSets.funcTest.runtimeClasspath
+    environment 'QUARKUS_VERSION', "${version}"
+    mustRunAfter test
+
+    // propagate the custom local maven repo, in case it's configured
+    if (System.properties.containsKey('maven.repo.local')) {
+        systemProperty 'maven.repo.local', System.properties.get('maven.repo.local')
+    }
+    testLogging {
+        events "passed", "skipped", "failed"
+    }
+    // Circumvent issue: https://github.com/gradle/gradle/issues/1675
+    systemProperty 'org.gradle.testkit.dir', file("${buildDir}/tmp/test-kit")
+}
+
+check.dependsOn functionalTest

devtools/gradle/src/funcTest/java/io/quarkus/gradle/functional/test/AdditionalSourceSetsTest.java

@@ -0,0 +1,47 @@
+package io.quarkus.gradle.functional.test;
+
+import org.gradle.testkit.runner.BuildResult;
+import org.gradle.testkit.runner.GradleRunner;
+import org.junit.jupiter.api.Test;
+
+import java.io.File;
+import java.net.URISyntaxException;
+import java.net.URL;
+
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+/**
+ * Functional test for verifying that the plugin can work with test sources which are included as part of a custom
+ * source set.
+ */
+public class AdditionalSourceSetsTest {
+
+    private static final String BUILD_FILE = "additional-source-sets/build.gradle";
+
+    @Test
+    public void executeFunctionalTest() throws URISyntaxException {
+        File buildFile = getBuildFile(BUILD_FILE);
+        GradleRunner runner = GradleRunner.create()
+                .withPluginClasspath()
+                .withProjectDir(buildFile.getParentFile());
+        BuildResult result = runner.withArguments(
+                "-s",
+                "-DQUARKUS_VERSION=" + System.getenv("QUARKUS_VERSION"),
+                "functionalTest")
+                .build();
+        String buildOutput = result.getOutput();
+        System.out.println(buildOutput);
+    }
+
+    /**
+     * Get the build file by searching for it on the classpath.
+     *
+     * @param path the path to the build file.
+     * @return the build file reference.
+     */
+    private File getBuildFile(String path) throws URISyntaxException {
+        URL resource = Thread.currentThread().getContextClassLoader().getResource(BUILD_FILE);
+        assertNotNull(resource, "Build file not found.");
+        return new File(resource.toURI());
+    }
+}

devtools/gradle/src/funcTest/resources/additional-source-sets/build.gradle

@@ -0,0 +1,55 @@
+plugins {
+    id 'java'
+    id 'io.quarkus'
+}
+
+repositories {
+    mavenLocal()
+    mavenCentral()
+}
+
+String quarkusVersion = System.getProperty('QUARKUS_VERSION')
+dependencies {
+    implementation "io.quarkus:quarkus-arc:${quarkusVersion}"
+    testImplementation "io.quarkus:quarkus-junit5:${quarkusVersion}"
+}
+
+sourceSets {
+    // Functional Tests
+    funcTest {
+        java.srcDir 'src/funcTest/java'
+        if (file('src/funcTest/resources').exists()) {
+            resources.srcDir 'src/funcTest/resources'
+        }
+
+        compileClasspath += sourceSets.main.output + configurations.testRuntimeClasspath + configurations.compileOnly
+        runtimeClasspath += output + compileClasspath
+    }
+}
+
+compileJava {
+    options.compilerArgs << '-parameters'
+}
+
+java {
+    sourceCompatibility = JavaVersion.VERSION_1_8
+    targetCompatibility = JavaVersion.VERSION_1_8
+}
+
+/*
+ * Functional tests for this module.
+ */
+task functionalTest(type: Test, description: 'Functional tests', dependsOn: [processResources, classes]) {
+    description = 'Run the functional tests.'
+    group = 'verification'
+
+    useJUnitPlatform()
+    testClassesDirs = sourceSets.funcTest.output.classesDirs
+    classpath = sourceSets.funcTest.runtimeClasspath
+
+    // Show standard streams on the console.
+    testLogging {
+        showStandardStreams = true
+    }
+    systemProperty 'quarkus.http.host', 'localhost'
+}

devtools/gradle/src/funcTest/resources/additional-source-sets/settings.gradle

@@ -0,0 +1 @@
+rootProject.name = 'functional-test'

devtools/gradle/src/funcTest/resources/additional-source-sets/src/funcTest/java/ft/SimpleBeanTest.java

@@ -0,0 +1,19 @@
+package ft;
+
+import javax.inject.Inject;
+import org.junit.jupiter.api.Test;
+import io.quarkus.test.junit.QuarkusTest;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+@QuarkusTest
+public class SimpleBeanTest {
+
+    @Inject
+    SimpleBean bean;
+
+    @Test
+    public void verify() {
+        assertEquals("hello", bean.hello(), "Did the implementation of the SimpleBean change?");
+    }
+}

devtools/gradle/src/funcTest/resources/additional-source-sets/src/main/java/ft/SimpleBean.java

@@ -0,0 +1,11 @@
+package ft;
+
+import javax.enterprise.context.ApplicationScoped;
+
+@ApplicationScoped
+public class SimpleBean {
+
+    public String hello() {
+        return "hello";
+    }
+}

devtools/gradle/src/funcTest/resources/additional-source-sets/src/main/resources/META-INF/beans.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<beans xmlns="http://xmlns.jcp.org/xml/ns/javaee"
+       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+       xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/beans_2_0.xsd"
+       bean-discovery-mode="all">
+</beans>

devtools/gradle/src/main/java/io/quarkus/gradle/QuarkusPluginExtension.java

@@ -73,7 +73,7 @@ void beforeTest(Test task) {
                                 project.relativePath(outputDirectory()));
                         joiner.add(mapping);
                     });
-            task.environment("TEST_TO_MAIN_MAPPINGS", joiner.toString());
+            task.environment(BootstrapConstants.TEST_TO_MAIN_MAPPINGS, joiner.toString());
 
             final String nativeRunner = task.getProject().getBuildDir().toPath().resolve(finalName() + "-runner")
                     .toAbsolutePath()

independent-projects/bootstrap/app-model/src/main/java/io/quarkus/bootstrap/BootstrapConstants.java

@@ -11,6 +11,12 @@ public interface BootstrapConstants {
     String SERIALIZED_APP_MODEL = "quarkus-internal.serialized-app-model.path";
     String DESCRIPTOR_FILE_NAME = "quarkus-extension.properties";
 
+    /**
+     * Constant for sharing the additional mappings between test-sources and the corresponding application-sources.
+     * The Gradle plugin populates this data which is then read by the PathTestHelper when executing tests.
+     */
+    String TEST_TO_MAIN_MAPPINGS = "TEST_TO_MAIN_MAPPINGS";
+
     @Deprecated
     String EXTENSION_PROPS_JSON_FILE_NAME = "quarkus-extension.json";
 

test-framework/common/src/main/java/io/quarkus/test/common/PathTestHelper.java

@@ -11,6 +11,7 @@
 import java.util.Map;
 import java.util.stream.Stream;
 
+import io.quarkus.bootstrap.BootstrapConstants;
 import io.quarkus.runtime.util.ClassPathUtils;
 
 /**
@@ -101,7 +102,7 @@ public final class PathTestHelper {
                 File.separator + "classes");
         //endregion
 
-        String mappings = System.getenv("TEST_TO_MAIN_MAPPINGS");
+        String mappings = System.getenv(BootstrapConstants.TEST_TO_MAIN_MAPPINGS);
         if (mappings != null) {
             Stream.of(mappings.split(","))
                     .filter(s -> !s.isEmpty())
@@ -110,7 +111,7 @@ public final class PathTestHelper {
                         if (entry.length == 2) {
                             TEST_TO_MAIN_DIR_FRAGMENTS.put(entry[0], entry[1]);
                         } else {
-                            System.err.println("Unable to parse additional test-to-main mapping: " + s);
+                            throw new IllegalStateException("Unable to parse additional test-to-main mapping: " + s);
                         }
                     });
         }