NullableOnMethodReturnType

src/main/java/org/openrewrite/staticanalysis/NullableOnMethodReturnType.java

@@ -0,0 +1,78 @@
+/*
+ * 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 org.openrewrite.staticanalysis;
+
+import org.openrewrite.ExecutionContext;
+import org.openrewrite.Recipe;
+import org.openrewrite.Tree;
+import org.openrewrite.TreeVisitor;
+import org.openrewrite.internal.ListUtils;
+import org.openrewrite.internal.lang.Nullable;
+import org.openrewrite.java.JavaIsoVisitor;
+import org.openrewrite.java.tree.J;
+import org.openrewrite.java.tree.Space;
+import org.openrewrite.marker.Markers;
+
+import java.util.Collections;
+
+import static org.openrewrite.java.trait.Traits.annotated;
+
+public class NullableOnMethodReturnType extends Recipe {
+
+    @Override
+    public String getDisplayName() {
+        return "Move `@Nullable` method annotations to the return type";
+    }
+
+    @Override
+    public String getDescription() {
+        return "This is the way the cool kids do it.";
+    }
+
+    @Override
+    public TreeVisitor<?, ExecutionContext> getVisitor() {
+        return new JavaIsoVisitor<ExecutionContext>() {
+            @Override
+            public J.MethodDeclaration visitMethodDeclaration(J.MethodDeclaration method, ExecutionContext ctx) {
+                J.MethodDeclaration m = super.visitMethodDeclaration(method, ctx);
+                return annotated(Nullable.class)
+                        .lower(getCursor())
+                        .findFirst()
+                        .map(nullable -> {
+                            if (nullable.getCursor().getParentTreeCursor().getValue() != m) {
+                                return m;
+                            }
+                            J.MethodDeclaration m2 = m;
+                            m2 = m2.withLeadingAnnotations(ListUtils.map(m2.getLeadingAnnotations(),
+                                    a -> a == nullable.getTree() ? null : a));
+                            if (m2 != m) {
+                                m2 = m2.withReturnTypeExpression(new J.AnnotatedType(
+                                        Tree.randomId(),
+                                        Space.SINGLE_SPACE,
+                                        Markers.EMPTY,
+                                        Collections.singletonList(nullable.getTree().withPrefix(Space.SINGLE_SPACE)),
+                                        m2.getReturnTypeExpression()
+                                ));
+                                m2 = autoFormat(m2, m2.getReturnTypeExpression(), ctx, getCursor().getParentOrThrow());
+                                m2 = m2.withPrefix(m2.getPrefix().withWhitespace(m2.getPrefix().getWhitespace().replace("\n\n\n", "\n\n")));
+                            }
+                            return m2;
+                        })
+                        .orElse(m);
+            }
+        };
+    }
+}

src/test/java/org/openrewrite/staticanalysis/NullableOnMethodReturnTypeTest.java

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+/*
+ * 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 org.openrewrite.staticanalysis;
+
+import org.junit.jupiter.api.Test;
+import org.openrewrite.test.RecipeSpec;
+import org.openrewrite.test.RewriteTest;
+
+import static org.openrewrite.java.Assertions.java;
+
+class NullableOnMethodReturnTypeTest implements RewriteTest {
+
+    @Override
+    public void defaults(RecipeSpec spec) {
+        spec.recipe(new NullableOnMethodReturnType());
+    }
+
+    @Test
+    void nullableOnMethodReturnType() {
+        rewriteRun(
+          //language=java
+          java(
+            """
+              import org.openrewrite.internal.lang.Nullable;
+              class Test {
+                  @Nullable
+                  public String test() {
+                  }
+              }
+              """,
+            """
+              import org.openrewrite.internal.lang.Nullable;
+              class Test {
+                  public @Nullable String test() {
+                  }
+              }
+              """
+          )
+        );
+    }
+
+    @Test
+    void dontTouchArguments() {
+        rewriteRun(
+          java(
+            //language=java
+            """
+              import org.openrewrite.internal.lang.Nullable;
+              class Test {
+                  void test(@Nullable String s) {
+                  }
+              }
+              """
+          )
+        );
+    }
+}