Support incremental annotation processing.

butterknife-compiler/src/main/java/butterknife/compiler/BindingSet.java

@@ -22,6 +22,8 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+
+import javax.lang.model.element.Element;
 import javax.lang.model.element.Modifier;
 import javax.lang.model.element.TypeElement;
 import javax.lang.model.type.TypeMirror;
@@ -82,13 +84,13 @@ private BindingSet(TypeName targetTypeName, ClassName bindingClassName, boolean
     this.parentBinding = parentBinding;
   }
 
-  JavaFile brewJava(int sdk, boolean debuggable) {
-    return JavaFile.builder(bindingClassName.packageName(), createType(sdk, debuggable))
+  JavaFile brewJava(int sdk, boolean debuggable, Element originatingElement) {
+    return JavaFile.builder(bindingClassName.packageName(), createType(sdk, debuggable, originatingElement))
         .addFileComment("Generated code from Butter Knife. Do not modify!")
         .build();
   }
 
-  private TypeSpec createType(int sdk, boolean debuggable) {
+  private TypeSpec createType(int sdk, boolean debuggable, Element originatingElement) {
     TypeSpec.Builder result = TypeSpec.classBuilder(bindingClassName.simpleName())
         .addModifiers(PUBLIC);
     if (isFinal) {
@@ -122,6 +124,8 @@ private TypeSpec createType(int sdk, boolean debuggable) {
       result.addMethod(createBindingUnbindMethod(result));
     }
 
+    result.addOriginatingElement(originatingElement);
+
     return result.build();
   }
 

butterknife-compiler/src/main/java/butterknife/compiler/ButterKnifeProcessor.java

@@ -50,12 +50,14 @@
 import java.util.Arrays;
 import java.util.BitSet;
 import java.util.Deque;
+import java.util.HashMap;
 import java.util.LinkedHashMap;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.HashSet;
 import java.util.Map;
 import java.util.Set;
+
 import javax.annotation.processing.AbstractProcessor;
 import javax.annotation.processing.Filer;
 import javax.annotation.processing.ProcessingEnvironment;
@@ -131,6 +133,7 @@ public final class ButterKnifeProcessor extends AbstractProcessor {
   private boolean debuggable = true;
 
   private final Map<QualifiedId, Id> symbols = new LinkedHashMap<>();
+  private HashMap<String, List<Element>> mapGeneratedFileToOriginatingElements = new LinkedHashMap<>();
 
   @Override public synchronized void init(ProcessingEnvironment env) {
     super.init(env);
@@ -198,9 +201,10 @@ private Set<Class<? extends Annotation>> getSupportedAnnotations() {
       TypeElement typeElement = entry.getKey();
       BindingSet binding = entry.getValue();
 
-      JavaFile javaFile = binding.brewJava(sdk, debuggable);
+      JavaFile javaFile = binding.brewJava(sdk, debuggable, typeElement);
       try {
         javaFile.writeTo(filer);
+        mapGeneratedFileToOriginatingElements.put(javaFile.toJavaFileObject().getName(), javaFile.typeSpec.originatingElements);
       } catch (IOException e) {
         error(typeElement, "Unable to write binding for type %s: %s", typeElement, e.getMessage());
       }
@@ -209,6 +213,10 @@ private Set<Class<? extends Annotation>> getSupportedAnnotations() {
     return false;
   }
 
+  public HashMap<String, List<Element>> getMapGeneratedFileToOriginatingElements() {
+    return mapGeneratedFileToOriginatingElements;
+  }
+
   private Map<TypeElement, BindingSet> findAndParseTargets(RoundEnvironment env) {
     Map<TypeElement, BindingSet.Builder> builderMap = new LinkedHashMap<>();
     Set<TypeElement> erasedTargetNames = new LinkedHashSet<>();

butterknife-compiler/src/main/resources/META-INF/gradle/incremental.annotation.processors

@@ -0,0 +1 @@
+butterknife.compiler.ButterKnifeProcessor,isolating

butterknife/src/test/java/butterknife/BindViewTest.java

@@ -3,14 +3,21 @@
 import butterknife.compiler.ButterKnifeProcessor;
 import com.google.common.collect.ImmutableList;
 import com.google.testing.compile.JavaFileObjects;
+
+import javax.lang.model.element.Element;
 import javax.tools.JavaFileObject;
 import javax.tools.StandardLocation;
+
 import org.junit.Test;
 
+import java.util.List;
+import java.util.Map;
+
 import static com.google.common.truth.Truth.assertAbout;
 import static com.google.testing.compile.JavaSourceSubjectFactory.javaSource;
 import static com.google.testing.compile.JavaSourcesSubjectFactory.javaSources;
 import static java.util.Arrays.asList;
+import static junit.framework.Assert.assertEquals;
 
 public class BindViewTest {
   @Test public void bindingView() {
@@ -50,12 +57,21 @@ public class BindViewTest {
         + "}"
     );
 
+    ButterKnifeProcessor butterKnifeProcessor = new ButterKnifeProcessor();
     assertAbout(javaSource()).that(source)
         .withCompilerOptions("-Xlint:-processing")
-        .processedWith(new ButterKnifeProcessor())
+        .processedWith(butterKnifeProcessor)
         .compilesWithoutWarnings()
         .and()
         .generatesSources(bindingSource);
+
+    Map<String, List<Element>> map = butterKnifeProcessor.getMapGeneratedFileToOriginatingElements();
+    assertEquals(1, map.size());
+    Map.Entry<String, List<Element>> entry = map.entrySet().iterator().next();
+    assertEquals("test/Test_ViewBinding.java", entry.getKey());
+    List<Element> elements = entry.getValue();
+    assertEquals(1, elements.size());
+    assertEquals("test.Test", elements.get(0).asType().toString());
   }
 
   @Test public void bindingViewNonDebuggable() {

gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions-snapshots/gradle-4.7-20180323002511+0000-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.5.1-all.zip