Auto add the maven plugin

inject-generator/src/main/java/io/avaje/inject/generator/InjectProcessor.java

@@ -28,7 +28,7 @@
 @GenerateUtils
 @GenerateAPContext
 @GenerateModuleInfoReader
-@SupportedOptions("mergeServices")
+@SupportedOptions({"mergeServices", "buildPlugin"})
 @SupportedAnnotationTypes({
   AspectImportPrism.PRISM_TYPE,
   AssistFactoryPrism.PRISM_TYPE,
@@ -88,6 +88,8 @@ public synchronized void init(ProcessingEnvironment processingEnv) {
         addition.append("avaje-inject-generator");
       }
       Files.writeString(file, addition.toString(), StandardOpenOption.CREATE, StandardOpenOption.WRITE);
+
+      PomPluginWriter.addPlugin2Pom();
     } catch (IOException e) {
       // not an issue worth failing over
     }

inject-generator/src/main/java/io/avaje/inject/generator/PomPluginWriter.java

@@ -0,0 +1,63 @@
+package io.avaje.inject.generator;
+
+import javax.lang.model.element.ModuleElement;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.StandardOpenOption;
+
+final class PomPluginWriter {
+
+  private static final String plugin =
+      "  <!-- generated by avaje inject -->\n"
+          + "      <plugin>\n"
+          + "        <groupId>io.avaje</groupId>\n"
+          + "        <artifactId>avaje-inject-maven-plugin</artifactId>\n"
+          + "        <version>%s</version>\n"
+          + "        <executions>\n"
+          + "          <execution>\n"
+          + "            <phase>process-sources</phase>\n"
+          + "            <goals>\n"
+          + "              <goal>provides</goal>\n"
+          + "            </goals>\n"
+          + "          </execution>\n"
+          + "        </executions>\n"
+          + "      </plugin>\n"
+          + "    ";
+
+  static void addPlugin2Pom() throws IOException {
+    var module = APContext.getProjectModuleElement();
+    // don't need mvn plugin with JPMS
+    if (disabledOrUsingModulePath(module)) {
+      return;
+    }
+
+    var pomPath = APContext.getBuildResource("").getParent().resolve("pom.xml");
+    if (!pomPath.toFile().exists()) {
+      return;
+    }
+
+    var pomContent = Files.readString(pomPath);
+    // don't need mvn plugin if not using mvn compiler annotationProcessors
+    if (pomContent.contains("avaje-inject-maven-plugin")
+        || !pomContent.contains("<annotationProcessors>")
+            && !pomContent.contains("<annotationProcessorPaths>")) {
+      return;
+    }
+    APContext.logNote("Adding avaje-inject-maven-plugin Plugin to pom");
+    var pluginsIndex = pomContent.indexOf("</plugins>");
+    var builder = new StringBuilder(pomContent);
+    if (pluginsIndex != -1) {
+      builder.insert(
+          pluginsIndex,
+          String.format(plugin, PomPluginWriter.class.getPackage().getImplementationVersion()));
+
+      Files.writeString(
+          pomPath, builder.toString(), StandardOpenOption.CREATE, StandardOpenOption.WRITE);
+    }
+  }
+
+  private static boolean disabledOrUsingModulePath(ModuleElement module) {
+    return !APContext.getOption("buildPlugin").map(Boolean::valueOf).orElse(true)
+      || module != null && !module.isUnnamed();
+  }
+}

inject-test/pom.xml

@@ -131,6 +131,9 @@
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-compiler-plugin</artifactId>
         <configuration>
+          <compilerArgs>
+            <arg>-AbuildPlugin=false</arg>
+          </compilerArgs>
           <annotationProcessorPaths>
             <path>
               <groupId>io.avaje</groupId>
@@ -140,7 +143,6 @@
           </annotationProcessorPaths>
         </configuration>
       </plugin>
-
     </plugins>
   </build>
 </project>