Change mutable public collections to immutable versions: ref issue #2413

rewrite-java/src/main/java/org/openrewrite/java/recipes/ArraysAsListToImmutableRecipe.java

@@ -0,0 +1,83 @@
+/*
+ * Copyright 2023 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.java.recipes;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import lombok.EqualsAndHashCode;
+import lombok.Value;
+import org.openrewrite.ExecutionContext;
+import org.openrewrite.Recipe;
+import org.openrewrite.TreeVisitor;
+import org.openrewrite.java.JavaIsoVisitor;
+import org.openrewrite.java.JavaTemplate;
+import org.openrewrite.java.MethodMatcher;
+import org.openrewrite.java.tree.J;
+
+/**
+ * This recipe modifies the invocation of a method so that it returns an unmodifiable list, if the
+ * method returns a modifiable one.
+ */
+@Value
+@EqualsAndHashCode(callSuper = true)
+public class ArraysAsListToImmutableRecipe extends Recipe {
+
+    @JsonCreator
+    public ArraysAsListToImmutableRecipe() {
+    }
+
+    @Override
+    public String getDisplayName() {
+        return "Wrap list to be unmodifiable";
+    }
+
+    @Override
+    public String getDescription() {
+        return "Return an unmodifiable list, if the method returns a modifiable list.";
+    }
+
+    @Override
+    public TreeVisitor<?, ExecutionContext> getVisitor() {
+        return new UnmodifiableListVisitor();
+    }
+
+    private static class UnmodifiableListVisitor extends JavaIsoVisitor<ExecutionContext> {
+
+        final MethodMatcher asListMatcher = new MethodMatcher("java.util.Arrays asList(..)");
+        final MethodMatcher unmodifiableListMatcher =
+                new MethodMatcher("java.util.Collections unmodifiableList(..)");
+
+        @Override
+        public J.MethodInvocation visitMethodInvocation(
+                final J.MethodInvocation method, final ExecutionContext executionContext) {
+            J.MethodInvocation result = super.visitMethodInvocation(method, executionContext);
+            if (asListMatcher.matches(method, true)) {
+                final J.MethodInvocation parentInvocation =
+                        getCursor().getParentOrThrow().firstEnclosing(J.MethodInvocation.class);
+                if (unmodifiableListMatcher.matches(parentInvocation, true)) {
+                    return super.visitMethodInvocation(method, executionContext);
+                }
+                result =
+                        JavaTemplate.builder("Collections.unmodifiableList(#{any()})")
+                                .imports("java.util.Collections", "java.util.Arrays")
+                                .contextSensitive()
+                                .build()
+                                .apply(getCursor(), method.getCoordinates().replace(), method);
+                maybeAddImport("java.util.Collections");
+            }
+            return result;
+        }
+    }
+}

rewrite-java/src/test/java/.editorconfig

@@ -0,0 +1,5 @@
+root = true
+
+[*.java]
+indent_size = 4
+ij_continuation_indent_size = 2

rewrite-java/src/test/java/org/openrewrite/java/recipes/ArraysAsListToImmutableRecipeTest.java

@@ -0,0 +1,112 @@
+/*
+ * Copyright 2023 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.java.recipes;
+
+import org.junit.jupiter.api.Test;
+import org.openrewrite.test.RecipeSpec;
+import org.openrewrite.test.RewriteTest;
+
+import static org.openrewrite.java.Assertions.java;
+
+class ArraysAsListToImmutableRecipeTest implements RewriteTest {
+
+    @Override
+    public void defaults(RecipeSpec spec) {
+        spec.recipe(new ArraysAsListToImmutableRecipe());
+    }
+
+    @Test
+    void wrapArrayListToBeUnmodifiableWhenStrings() {
+        rewriteRun(
+          java("""
+              import java.util.Arrays;
+
+              class A {
+                 public static final List<String> entries = Arrays.asList("A", "B");
+              }
+              """,
+            """
+              import java.util.Arrays;
+              import java.util.Collections;
+
+              class A {
+                 public static final List<String> entries = Collections.unmodifiableList(Arrays.asList("A", "B"));
+              }
+              """
+          )
+        );
+    }
+
+    @Test
+    void wrapArrayListToBeUnmodifiableWhenNulls() {
+        rewriteRun(
+          java("""
+              import java.util.Arrays;
+
+              class A {
+                 public static final List<String> entries = Arrays.asList("A", null);
+              }
+              """,
+            """
+              import java.util.Arrays;
+              import java.util.Collections;
+
+              class A {
+                 public static final List<String> entries = Collections.unmodifiableList(Arrays.asList("A", null));
+              }
+              """
+          )
+        );
+    }
+
+
+    @Test
+    void wrapArrayListToBeUnmodifiableWhenIntegers() {
+        rewriteRun(
+          java("""
+              import java.util.Arrays;
+
+              class A {
+                 public static final List<Integer> entries = Arrays.asList(1, 2);
+              }
+              """,
+            """
+              import java.util.Arrays;
+              import java.util.Collections;
+
+              class A {
+                 public static final List<Integer> entries = Collections.unmodifiableList(Arrays.asList(1, 2));
+              }
+              """
+          )
+        );
+    }
+
+    @Test
+    void doNotWrapIfItIsAlreadyUnmodifiable() {
+        rewriteRun(
+          java("""
+            import java.util.Arrays;
+            import java.util.Collections;
+
+            class A {
+               public static final List<String> entries = Collections.unmodifiableList(Arrays.asList("A", "B"));
+            }
+            """
+          )
+        );
+    }
+}