react to external plugins

Author: TheSnoozer

src/main/java/io/github/git/commit/id/gradle/plugin/GitCommitIdPlugin.java

@@ -18,11 +18,17 @@
 package io.github.git.commit.id.gradle.plugin;
 
 import groovy.lang.Closure;
+
+import java.util.Arrays;
 import java.util.Map;
 import java.util.Properties;
 import org.gradle.api.Plugin;
 import org.gradle.api.Project;
 import org.gradle.api.plugins.ExtensionAware;
+import org.gradle.api.plugins.JavaPlugin;
+import org.gradle.api.plugins.scala.ScalaPlugin;
+import org.gradle.api.tasks.SourceSet;
+import org.gradle.api.tasks.SourceSetContainer;
 import pl.project13.core.CommitIdPropertiesOutputFormat;
 import pl.project13.core.GitCommitIdExecutionException;
 import pl.project13.core.util.GenericFileManager;
@@ -163,6 +169,18 @@ public void apply(Project project) {
             GitCommitIdPluginGenerationTask.class);
         task.onlyIf(ignore -> extension.getSkip().get() == false);
 
+        // React to external plugins
+        // See https://docs.gradle.org/current/userguide/implementing_gradle_plugins.html#reacting_to_plugins
+        project.getTasks().named(JavaPlugin.CLASSES_TASK_NAME).configure(
+          classesTask -> classesTask.dependsOn(task));
+
+        project.getPlugins().withType(JavaPlugin.class, javaPlugin -> {
+            SourceSetContainer sourceSets = project.getExtensions().getByType(SourceSetContainer.class);
+            SourceSet main = sourceSets.getByName(SourceSet.MAIN_SOURCE_SET_NAME);
+            main.getJava().setSrcDirs(Arrays.asList(task.getOutput().getAsFile().get()));
+        });
+
+        // Expose the generated properties
         project
           .getExtensions()
           .getExtraProperties()