added support for Gradles incremental annotation processing

this fixes #6

Author: tmtron

.idea/modules/enum-mapper-processor/enum-mapper-processor_main.iml

@@ -6,10 +6,15 @@ dependencies {
     compile project(':enum-mapper-lib')
 
     compile 'com.squareup:javapoet:1.11.1'
+    compile 'com.google.auto:auto-common:0.10'
     // unfortunately lib and processor are in the same artifact
     // see: https://github.com/google/auto/issues/632
     compileOnly 'com.google.auto.service:auto-service:1.0-rc4'
-    compile 'com.google.auto:auto-common:0.10'
+
+    // https://github.com/tbroyer/gradle-incap-helper
+    final INCAP_VERSION = '0.1'
+    compileOnly("net.ltgt.gradle.incap:incap:${INCAP_VERSION}")
+    annotationProcessor("net.ltgt.gradle.incap:incap-processor:${INCAP_VERSION}")
 
     testCompile 'com.google.testing.compile:compile-testing:0.15'
     testCompile 'com.google.truth:truth:0.40'

enum-mapper-processor/build.gradle

@@ -18,6 +18,9 @@
 import com.google.auto.common.BasicAnnotationProcessor;
 import com.google.auto.service.AutoService;
 
+import net.ltgt.gradle.incap.IncrementalAnnotationProcessor;
+import net.ltgt.gradle.incap.IncrementalAnnotationProcessorType;
+
 import java.util.Collections;
 
 import javax.annotation.processing.Processor;
@@ -27,6 +30,7 @@
  * This class will register the annotation processor/s.
  */
 @AutoService(Processor.class)
+@IncrementalAnnotationProcessor(IncrementalAnnotationProcessorType.AGGREGATING)
 public class EnumsAnnotationProcessor extends BasicAnnotationProcessor {
 
     @Override

enum-mapper-processor/src/main/java/com/tmtron/enums/processor/EnumsAnnotationProcessor.java

@@ -54,8 +54,7 @@ public Set<? extends Class<? extends Annotation>> annotations() {
     @Override
     public Set<Element> process(SetMultimap<Class<? extends Annotation>, Element> elementsByAnnotation) {
         try {
-            Map<Class<? extends Annotation>, Collection<Element>> annotationsMap =
-                    elementsByAnnotation.asMap();
+            Map<Class<? extends Annotation>, Collection<Element>> annotationsMap = elementsByAnnotation.asMap();
             // the annotations() method tells the framework which annotations to accept
             if (annotationsMap.keySet().size() > 2) throw new RuntimeException("Too many annotations");
 

enum-mapper-processor/src/main/java/com/tmtron/enums/processor/MapAllEnumsProcessingStep.java

@@ -129,8 +129,13 @@ private void addStagedBuilderInterfaces(TypeSpec.Builder mapperFullTypeBuilder
     private TypeSpec.Builder createFullMapperTypeSpecBuilder() {
         // LauncherAge_MapperFull
         ClassName className = ClassName.bestGuess(enumsClassTypeElement.getQualifiedName() + "_MapperFull");
-        TypeSpec.Builder result = TypeSpec.classBuilder(className).addModifiers(Modifier.PUBLIC,
-                Modifier.FINAL);
+        TypeSpec.Builder result = TypeSpec.classBuilder(className).addModifiers(Modifier.PUBLIC, Modifier.FINAL);
+
+        /*
+         * We must add the originating elements in order to use Gradles "Incremental annotation processing"
+         * https://docs.gradle.org/4.8-rc-2/userguide/java_plugin.html#sec:incremental_annotation_processing
+         */
+        annotatedElements.forEach(result::addOriginatingElement);
         // @Generated annotation
         result.addAnnotation(
                 createGeneratedAnnotation(EnumsAnnotationProcessor.class)