Merge pull request #226 from google/catch.duplicate.registration

Disable duplicate Processor registrations

Author: hdurer

src/main/java/org/inferred/freebuilder/processor/Processor.java

@@ -25,6 +25,7 @@
 import com.google.common.base.Objects;
 import com.google.common.base.Throwables;
 import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.MapMaker;
 
 import org.inferred.freebuilder.FreeBuilder;
 import org.inferred.freebuilder.processor.util.CompilationUnitBuilder;
@@ -34,6 +35,7 @@
 
 import java.io.IOException;
 import java.util.Set;
+import java.util.concurrent.ConcurrentMap;
 
 import javax.annotation.processing.AbstractProcessor;
 import javax.annotation.processing.FilerException;
@@ -53,6 +55,14 @@
 @AutoService(javax.annotation.processing.Processor.class)
 public class Processor extends AbstractProcessor {
 
+  /**
+   * Keep track of which processors have been registered to avoid double-processing if FreeBuilder
+   * ends up on the processor path twice. While we catch the resulting Filer exceptions and convert
+   * them to warnings, it's still cleaner to issue a single NOTE-severity message.
+   */
+  private static final ConcurrentMap<ProcessingEnvironment, Processor> registeredProcessors =
+      new MapMaker().weakKeys().weakValues().concurrencyLevel(1).initialCapacity(1).makeMap();
+
   private Analyser analyser;
   private final CodeGenerator codeGenerator = new CodeGenerator();
   private final FeatureSet features;
@@ -81,6 +91,11 @@ public SourceVersion getSupportedSourceVersion() {
   @Override
   public synchronized void init(ProcessingEnvironment processingEnv) {
     super.init(processingEnv);
+    if (registeredProcessors.putIfAbsent(processingEnv, this) != null) {
+      processingEnv.getMessager().printMessage(
+          Kind.NOTE, "FreeBuilder processor registered twice; disabling duplicate instance");
+      return;
+    }
     analyser = new Analyser(
         processingEnv.getElementUtils(),
         processingEnv.getMessager(),
@@ -93,6 +108,10 @@ public synchronized void init(ProcessingEnvironment processingEnv) {
 
   @Override
   public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
+    if (analyser == null) {
+      // Another FreeBuilder Processor is already registered; skip processing
+      return false;
+    }
     for (TypeElement type : typesIn(annotatedElementsIn(roundEnv, FreeBuilder.class))) {
       try {
         Metadata metadata = analyser.analyse(type);

src/test/java/org/inferred/freebuilder/processor/ProcessorTest.java

@@ -1105,4 +1105,22 @@ public void testJacksonInteroperability() {
         .runTest();
   }
 
+  @Test
+  public void testDoubleRegistration() {
+    // See also https://github.com/google/FreeBuilder/issues/21
+    behaviorTester
+        .with(new Processor(features))
+        .with(new Processor(features))
+        .with(TWO_PROPERTY_FREE_BUILDER_INTERFACE)
+        .with(new TestBuilder()
+            .addLine("com.example.DataType value = new com.example.DataType.Builder()")
+            .addLine("    .setPropertyA(11)")
+            .addLine("    .setPropertyB(true)")
+            .addLine("    .build();")
+            .addLine("assertEquals(11, value.getPropertyA());")
+            .addLine("assertTrue(value.isPropertyB());")
+            .build())
+        .compiles()
+        .withNoWarnings();
+  }
 }