Skip method references and lambdas in body

build.gradle.kts

@@ -130,14 +130,15 @@ configure<PublishingExtension> {
             suppressPomMetadataWarningsFor("runtimeElements")
 
             pom.withXml {
-                (asElement().getElementsByTagName("dependencies").item(0) as org.w3c.dom.Element?)?.let { dependencies ->
+                (asElement().getElementsByTagName("dependencies")
+                    .item(0) as org.w3c.dom.Element?)?.let { dependencies ->
                     dependencies.getElementsByTagName("dependency").let { dependencyList ->
                         var i = 0
                         var length = dependencyList.length
                         while (i < length) {
                             (dependencyList.item(i) as org.w3c.dom.Element).let { dependency ->
                                 if ((dependency.getElementsByTagName("scope")
-                                                .item(0) as org.w3c.dom.Element).textContent == "provided"
+                                        .item(0) as org.w3c.dom.Element).textContent == "provided"
                                 ) {
                                     dependencies.removeChild(dependency)
                                     i--
@@ -156,12 +157,12 @@ configure<PublishingExtension> {
 val signingKey: String? by project
 val signingPassword: String? by project
 val requireSigning = project.hasProperty("forceSigning") || project.hasProperty("releasing")
-if(signingKey != null && signingPassword != null) {
+if (signingKey != null && signingPassword != null) {
     signing {
         isRequired = requireSigning
         useInMemoryPgpKeys(signingKey, signingPassword)
         sign(publishing.publications["nebula"])
     }
-} else if(requireSigning) {
+} else if (requireSigning) {
     throw RuntimeException("Artifact signing is required, but signingKey and/or signingPassword are null")
 }

src/main/java/org/openrewrite/java/template/processor/RefasterTemplateProcessor.java

@@ -106,6 +106,11 @@ public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment
                 maybeGenerateTemplateSources(jcCompilationUnit);
             }
         }
+
+        // Inform how many rules were skipped and why; useful for debugging, but not enabled by default
+        //printedMessages.entrySet().stream().sorted(Map.Entry.comparingByValue())
+        //        .forEach(entry -> processingEnv.getMessager().printMessage(Kind.NOTE, entry.toString()));
+
         // Give other annotation processors a chance to process the same annotations, for dual use of Refaster templates
         return false;
     }
@@ -750,9 +755,9 @@ private TemplateDescriptor validate(Context context, JCCompilationUnit cu) {
             boolean valid = resolve(context, cu);
             if (valid) {
                 for (JCTree.JCMethodDecl template : beforeTemplates) {
-                    valid &= validateTemplateMethod(template);
+                    valid = valid && validateTemplateMethod(template);
                 }
-                valid &= validateTemplateMethod(afterTemplate);
+                valid = valid && validateTemplateMethod(afterTemplate);
             }
             return valid ? this : null;
         }
@@ -784,6 +789,16 @@ private boolean validateTemplateMethod(JCTree.JCMethodDecl template) {
                 printNoteOnce("If statements are currently not supported", classDecl.sym);
                 return false;
             }
+            if (template.body.stats.get(0) instanceof JCTree.JCReturn) {
+                JCTree.JCExpression expr = ((JCTree.JCReturn) template.body.stats.get(0)).expr;
+                if (expr instanceof JCTree.JCLambda) {
+                    printNoteOnce("Lambdas are currently not supported", classDecl.sym);
+                    return false;
+                } else if (expr instanceof JCTree.JCMemberReference) {
+                    printNoteOnce("Method references are currently not supported", classDecl.sym);
+                    return false;
+                }
+            }
             return new TreeScanner() {
                 boolean valid = true;
 

src/test/java/org/openrewrite/java/template/RefasterTemplateProcessorTest.java

@@ -19,12 +19,14 @@
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
 import com.google.testing.compile.Compilation;
 import com.google.testing.compile.JavaFileObjects;
+import org.intellij.lang.annotations.Language;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.ValueSource;
 import org.openrewrite.java.template.processor.RefasterTemplateProcessor;
 import org.openrewrite.java.template.processor.TypeAwareProcessor;
 
+import javax.tools.JavaFileObject;
 import java.io.File;
 import java.net.URL;
 import java.util.Arrays;
@@ -45,7 +47,7 @@ class RefasterTemplateProcessorTest {
       "SimplifyBooleans",
     })
     void generateRecipe(String recipeName) {
-        Compilation compilation = compile("refaster/" + recipeName + ".java");
+        Compilation compilation = compileResource("refaster/" + recipeName + ".java");
         assertThat(compilation).succeeded();
         assertThat(compilation).hadNoteCount(0);
         assertThat(compilation)
@@ -55,7 +57,7 @@ void generateRecipe(String recipeName) {
 
     @Test
     void generateRecipeInDefaultPackage() {
-        Compilation compilation = compile("refaster/UnnamedPackage.java");
+        Compilation compilation = compileResource("refaster/UnnamedPackage.java");
         assertThat(compilation).succeeded();
         assertThat(compilation).hadNoteCount(0);
         assertThat(compilation)
@@ -69,7 +71,7 @@ void generateRecipeInDefaultPackage() {
       "RefasterAnyOf",
     })
     void skipRecipeGeneration(String recipeName) {
-        Compilation compilation = compile("refaster/" + recipeName + ".java");
+        Compilation compilation = compileResource("refaster/" + recipeName + ".java");
         assertThat(compilation).succeeded();
         assertEquals(0, compilation.generatedSourceFiles().size(), "Should not generate recipe for " + recipeName);
     }
@@ -85,20 +87,37 @@ void skipRecipeGeneration(String recipeName) {
       "SimplifyTernary",
     })
     void nestedRecipes(String recipeName) {
-        Compilation compilation = compile("refaster/" + recipeName + ".java");
+        Compilation compilation = compileResource("refaster/" + recipeName + ".java");
         assertThat(compilation).succeeded();
         assertThat(compilation).hadNoteCount(0);
         assertThat(compilation) // Recipes (plural)
           .generatedSourceFile("foo/" + recipeName + "Recipes")
           .hasSourceEquivalentTo(JavaFileObjects.forResource("refaster/" + recipeName + "Recipes.java"));
     }
 
-    private static Compilation compile(String resourceName) {
-        return compile(resourceName, new RefasterTemplateProcessor());
+    @Test
+    void stringIsEmptyPredicate() {
+        Compilation compilation = compileResource("refaster/StringIsEmptyPredicate.java");
+        assertThat(compilation).succeeded();
+        assertThat(compilation).hadNoteCount(1);
+        assertThat(compilation).hadNoteContaining("Lambdas are currently not supported");
+        assertEquals(0, compilation.generatedSourceFiles().size(), "Not yet supported");
+    }
+
+    private static Compilation compileResource(String resourceName) {
+        return compileResource(resourceName, new RefasterTemplateProcessor());
     }
 
-    static Compilation compile(String resourceName, TypeAwareProcessor processor) {
+    static Compilation compileResource(String resourceName, TypeAwareProcessor processor) {
         // As per https://github.com/google/compile-testing/blob/v0.21.0/src/main/java/com/google/testing/compile/package-info.java#L53-L55
+        return compileResource(JavaFileObjects.forResource(resourceName), processor);
+    }
+
+    static Compilation compileSource(String fqn, @Language("java") String source, TypeAwareProcessor processor) {
+        return compileResource(JavaFileObjects.forSourceString(fqn, source), processor);
+    }
+
+    static Compilation compileResource(JavaFileObject javaFileObject, TypeAwareProcessor processor) {
         return javac()
           .withProcessors(processor)
           .withClasspath(Arrays.asList(
@@ -110,7 +129,7 @@ static Compilation compile(String resourceName, TypeAwareProcessor processor) {
             fileForClass(org.slf4j.Logger.class),
             fileForClass(Primitive.class)
           ))
-          .compile(JavaFileObjects.forResource(resourceName));
+          .compile(javaFileObject);
     }
 
     // As per https://github.com/google/auto/blob/auto-value-1.10.2/factory/src/test/java/com/google/auto/factory/processor/AutoFactoryProcessorTest.java#L99

src/test/java/org/openrewrite/java/template/TemplateProcessorTest.java

@@ -23,7 +23,7 @@
 import org.openrewrite.java.template.processor.TemplateProcessor;
 
 import static com.google.testing.compile.CompilationSubject.assertThat;
-import static org.openrewrite.java.template.RefasterTemplateProcessorTest.compile;
+import static org.openrewrite.java.template.RefasterTemplateProcessorTest.compileResource;
 
 class TemplateProcessorTest {
     @ParameterizedTest
@@ -35,7 +35,7 @@ class TemplateProcessorTest {
     })
     void qualification(String qualifier) {
         // As per https://github.com/google/compile-testing/blob/v0.21.0/src/main/java/com/google/testing/compile/package-info.java#L53-L55
-        Compilation compilation = compile("template/ShouldAddClasspathRecipes.java", new TemplateProcessor());
+        Compilation compilation = compileResource("template/ShouldAddClasspathRecipes.java", new TemplateProcessor());
         assertThat(compilation).succeeded();
         assertThat(compilation)
           .generatedSourceFile("foo/ShouldAddClasspathRecipes$" + qualifier + "Recipe$1_before")
@@ -47,7 +47,7 @@ void qualification(String qualifier) {
 
     @Test
     void parameterReuse() {
-        Compilation compilation = compile("template/ParameterReuseRecipe.java", new TemplateProcessor());
+        Compilation compilation = compileResource("template/ParameterReuseRecipe.java", new TemplateProcessor());
         assertThat(compilation).succeeded();
         assertThat(compilation)
           .generatedSourceFile("foo/ParameterReuseRecipe$1_before")
@@ -56,7 +56,7 @@ void parameterReuse() {
 
     @Test
     void parserClasspath() {
-        Compilation compilation = compile("template/LoggerRecipe.java", new TemplateProcessor());
+        Compilation compilation = compileResource("template/LoggerRecipe.java", new TemplateProcessor());
         assertThat(compilation).succeeded();
         assertThat(compilation)
           .generatedSourceFile("template/LoggerRecipe$1_logger")
@@ -68,7 +68,7 @@ void parserClasspath() {
 
     @Test
     void generics() {
-        Compilation compilation = compile("template/Generics.java", new TemplateProcessor());
+        Compilation compilation = compileResource("template/Generics.java", new TemplateProcessor());
         assertThat(compilation).succeeded();
         assertThat(compilation)
           .generatedSourceFile("template/Generics$1_before")
@@ -80,7 +80,7 @@ void generics() {
 
     @Test
     void throwNew() {
-        Compilation compilation = compile("template/ThrowNewRecipe.java", new TemplateProcessor());
+        Compilation compilation = compileResource("template/ThrowNewRecipe.java", new TemplateProcessor());
         assertThat(compilation).succeeded();
         assertThat(compilation)
           .generatedSourceFile("template/ThrowNewRecipe$1_template")
@@ -89,7 +89,7 @@ void throwNew() {
 
     @Test
     void unnamedPackage() {
-        Compilation compilation = compile("template/UnnamedPackage.java", new TemplateProcessor());
+        Compilation compilation = compileResource("template/UnnamedPackage.java", new TemplateProcessor());
         assertThat(compilation).succeeded();
         assertThat(compilation)
           .generatedSourceFile("UnnamedPackage$1_message")

src/test/resources/refaster/StringIsEmptyPredicate.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2024 the original author or authors.
+ * <p>
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * https://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package refaster;
+
+import com.google.errorprone.refaster.annotation.AfterTemplate;
+import com.google.errorprone.refaster.annotation.BeforeTemplate;
+
+import java.util.function.Predicate;
+
+class StringIsEmptyPredicate {
+    @BeforeTemplate
+    Predicate<String> before() {
+        return s -> s.isEmpty();
+    }
+
+    @AfterTemplate
+    Predicate<String> after() {
+        return String::isEmpty;
+    }
+}