From a6e524cccef1417e2461fb33bfae25846c9166a2 Mon Sep 17 00:00:00 2001
From: Aleksandar A Simpson <alek@asu.me>
Date: Mon, 26 Jun 2023 02:56:51 -0700
Subject: [PATCH] Remove hashCode calls on arrays (#128)

* added first tests for recipe. All tests pass right now

* updated recipe displayName and description

* added RSPEC tags, switched assert statement for if statement and updated description

* Polish

- Remove `Preconditions.or` for single element
- Collapse `if` statements for select type check
- Inline `builder_string`, as variable name does not conform to Java standards & limited use & scope allows for inlining
- Remove unnecessary elements from test cases to prevent confusion
- Remove public visibility from test class

---------

Co-authored-by: Tim te Beek <tim@moderne.io>
---
 ...RemoveHashCodeCallsFromArrayInstances.java |  76 +++++++++++++
 ...veHashCodeCallsFromArrayInstancesTest.java | 101 ++++++++++++++++++
 2 files changed, 177 insertions(+)
 create mode 100644 src/main/java/org/openrewrite/staticanalysis/RemoveHashCodeCallsFromArrayInstances.java
 create mode 100644 src/test/java/org/openrewrite/staticanalysis/RemoveHashCodeCallsFromArrayInstancesTest.java

diff --git a/src/main/java/org/openrewrite/staticanalysis/RemoveHashCodeCallsFromArrayInstances.java b/src/main/java/org/openrewrite/staticanalysis/RemoveHashCodeCallsFromArrayInstances.java
new file mode 100644
index 000000000..fa01557bd
--- /dev/null
+++ b/src/main/java/org/openrewrite/staticanalysis/RemoveHashCodeCallsFromArrayInstances.java
@@ -0,0 +1,76 @@
+/*
+ * 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.staticanalysis;
+
+import org.openrewrite.ExecutionContext;
+import org.openrewrite.Preconditions;
+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.search.UsesMethod;
+import org.openrewrite.java.tree.Expression;
+import org.openrewrite.java.tree.J;
+import org.openrewrite.java.tree.JavaType;
+
+import java.util.Collections;
+import java.util.Set;
+
+public class RemoveHashCodeCallsFromArrayInstances extends Recipe {
+    private static final MethodMatcher HASHCODE_MATCHER = new MethodMatcher("java.lang.Object hashCode()");
+
+    @Override
+    public String getDisplayName() {
+        return "`hashCode()` should not be called on array instances";
+    }
+
+    @Override
+    public String getDescription() {
+        return "Replace `hashCode()` calls on arrays with `Arrays.hashCode()` because the results from `hashCode()`" +
+               " are not helpful.";
+    }
+
+    @Override
+    public Set<String> getTags() {
+        return Collections.singleton("RSPEC-2116");
+    }
+
+    @Override
+    public TreeVisitor<?, ExecutionContext> getVisitor() {
+        return Preconditions.check(new UsesMethod<>(HASHCODE_MATCHER), new RemoveHashCodeCallsFromArrayInstancesVisitor());
+    }
+
+    private static class RemoveHashCodeCallsFromArrayInstancesVisitor extends JavaIsoVisitor<ExecutionContext> {
+        @Override
+        public J.MethodInvocation visitMethodInvocation(J.MethodInvocation methodInvocation, ExecutionContext ctx) {
+            J.MethodInvocation mi = super.visitMethodInvocation(methodInvocation, ctx);
+
+            if (HASHCODE_MATCHER.matches(mi)) {
+                Expression select = mi.getSelect();
+                if (select != null && select.getType() instanceof JavaType.Array) {
+                    maybeAddImport("java.util.Arrays");
+                    return JavaTemplate.builder("Arrays.hashCode(#{anyArray(java.lang.Object)})")
+                            .imports("java.util.Arrays")
+                            .build()
+                            .apply(getCursor(), mi.getCoordinates().replace(), select);
+                }
+            }
+
+            return mi;
+        }
+    }
+}
diff --git a/src/test/java/org/openrewrite/staticanalysis/RemoveHashCodeCallsFromArrayInstancesTest.java b/src/test/java/org/openrewrite/staticanalysis/RemoveHashCodeCallsFromArrayInstancesTest.java
new file mode 100644
index 000000000..4bce2fe12
--- /dev/null
+++ b/src/test/java/org/openrewrite/staticanalysis/RemoveHashCodeCallsFromArrayInstancesTest.java
@@ -0,0 +1,101 @@
+/*
+ * 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.staticanalysis;
+
+import org.junit.jupiter.api.Test;
+import org.openrewrite.DocumentExample;
+import org.openrewrite.Issue;
+import org.openrewrite.test.RecipeSpec;
+import org.openrewrite.test.RewriteTest;
+
+import static org.openrewrite.java.Assertions.java;
+
+@SuppressWarnings("ArrayHashCode")
+class RemoveHashCodeCallsFromArrayInstancesTest implements RewriteTest {
+    @Override
+    public void defaults(RecipeSpec spec) {
+        spec.recipe(new RemoveHashCodeCallsFromArrayInstances());
+    }
+
+    @Test
+    @DocumentExample
+    @Issue("https://github.com/openrewrite/rewrite-static-analysis/issues/44")
+    void replaceHashCodeCalls() {
+        //language=java
+        rewriteRun(
+          java("""
+            class SomeClass {
+              public static void main(String[] args) {
+                int argHash = args.hashCode();
+              }
+            }
+            """, """
+            import java.util.Arrays;
+            
+            class SomeClass {
+              public static void main(String[] args) {
+                int argHash = Arrays.hashCode(args);
+              }
+            }
+            """)
+        );
+    }
+
+    @Test
+    void selectIsAMethod() {
+        //language=java
+        rewriteRun(
+          java("""
+            class SomeClass {
+              void foo() {
+                int hashCode = getArr().hashCode();
+              }
+              
+              public int[] getArr() {
+                return new int[]{1, 2, 3};
+              }
+            }
+            """, """
+            import java.util.Arrays;
+            
+            class SomeClass {
+              void foo() {
+                int hashCode = Arrays.hashCode(getArr());
+              }
+              
+              public int[] getArr() {
+                return new int[]{1, 2, 3};
+              }
+            }
+            """)
+        );
+    }
+
+    @Test
+    void onlyRunOnArrayInstances() {
+        //language=java
+        rewriteRun(
+          java("""
+            class SomeClass {
+              void foo() {
+                String name = "bill";
+                int hashCode = name.hashCode();
+              }
+            }
+            """)
+        );
+    }
+}