new recipe that changes .equals() to .contentEquals() when comparing …

gradle/licenseHeader.txt

@@ -1,4 +1,4 @@
-Copyright 2021 the original author or authors.
+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.

src/main/java/org/openrewrite/staticanalysis/EqualsToContentEquals.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.MethodMatcher;
+import org.openrewrite.java.search.UsesType;
+import org.openrewrite.java.tree.Expression;
+import org.openrewrite.java.tree.J;
+import org.openrewrite.java.tree.TypeUtils;
+
+import java.util.Collections;
+
+public class EqualsToContentEquals extends Recipe {
+    private static final TreeVisitor<?, ExecutionContext> PRECONDITION = Preconditions.or(
+            new UsesType<>("java.lang.CharSequence", false),
+            new UsesType<>("java.lang.StringBuffer", false),
+            new UsesType<>("java.lang.StringBuilder", false)
+    );
+
+    @Override
+    public String getDisplayName() {
+        return "Use `String.contentEquals(CharSequence)` instead of `String.equals(CharSequence.toString())`";
+    }
+
+    @Override
+    public String getDescription() {
+        return "Use `String.contentEquals(CharSequence)` instead of `String.equals(CharSequence.toString())`.";
+    }
+
+    public TreeVisitor<?, ExecutionContext> getVisitor() {
+        return Preconditions.check(PRECONDITION, new EqualsToContentEqualsVisitor());
+    }
+
+    private static class EqualsToContentEqualsVisitor extends JavaIsoVisitor<ExecutionContext> {
+        private static final MethodMatcher EQUALS_MATCHER = new MethodMatcher("String equals(Object)");
+        private static final MethodMatcher TOSTRING_MATCHER = new MethodMatcher("java.lang.* toString()");
+
+        @Override
+        public J.MethodInvocation visitMethodInvocation(J.MethodInvocation mi, ExecutionContext ctx) {
+            J.MethodInvocation m = super.visitMethodInvocation(mi, ctx);
+            if (!EQUALS_MATCHER.matches(m)) {
+                return m;
+            }
+            Expression equalsArgument = m.getArguments().get(0);
+            if (!TOSTRING_MATCHER.matches(equalsArgument)) {
+                return m;
+            }
+            J.MethodInvocation inv = (J.MethodInvocation) equalsArgument;
+            Expression toStringSelect = inv.getSelect();
+            if (toStringSelect == null || !TypeUtils.isAssignableTo("java.lang.CharSequence", toStringSelect.getType())) {
+                return m;
+            }
+            // Strip out the toString() on the argument and replace with contentEquals
+            return m.withArguments(Collections.singletonList(toStringSelect))
+                    .withName(m.getName().withSimpleName("contentEquals"));
+        }
+    }
+}

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

@@ -0,0 +1,153 @@
+/*
+ * 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.java.JavaParser;
+import org.openrewrite.test.RecipeSpec;
+import org.openrewrite.test.RewriteTest;
+
+import static org.openrewrite.java.Assertions.java;
+
+class EqualsToContentEqualsTest implements RewriteTest {
+
+    @Override
+    public void defaults(RecipeSpec spec) {
+        spec
+          .parser(JavaParser.fromJavaVersion())
+          .recipe(new EqualsToContentEquals());
+    }
+
+    @Test
+    @DocumentExample
+    void replaceStringBuilder() {
+        //language=java
+        rewriteRun(
+          java(
+            """
+              class SomeClass {
+                  boolean foo(StringBuilder sb) {
+                      String str = "example string";
+                      return str.equals(sb.toString());
+                  }
+              }
+              """,
+            """
+              class SomeClass {
+                  boolean foo(StringBuilder sb) {
+                      String str = "example string";
+                      return str.contentEquals(sb);
+                  }
+              }
+              """
+          )
+        );
+    }
+
+    @Test
+    void onlyRunsOnCorrectInvocations() {
+        //language=java
+        rewriteRun(
+          java(
+            """
+              class SomeClass {
+                  boolean foo(Integer number, String str) {
+                      return str.equals(number.toString());
+                  }
+              }
+              """
+          )
+        );
+    }
+
+    @Test
+    void runsOnStringBuffer() {
+        //language=java
+        rewriteRun(
+          java(
+            """
+              class SomeClass {
+                  boolean foo(StringBuffer sb, String str) {
+                      return str.equals(sb.toString());
+                  }
+              }
+              """,
+            """
+              class SomeClass {
+                  boolean foo(StringBuffer sb, String str) {
+                      return str.contentEquals(sb);
+                  }
+              }
+              """
+          )
+        );
+    }
+
+    @Test
+    void runsOnCharSequence() {
+        //language=java
+        rewriteRun(
+          java(
+            """
+              class SomeClass {
+                  boolean foo(CharSequence cs, String str) {
+                      return str.equals(cs.toString());
+                  }
+              }
+              """,
+            """
+              class SomeClass {
+                  boolean foo(CharSequence cs, String str) {
+                      return str.contentEquals(cs);
+                  }
+              }
+              """
+          )
+        );
+    }
+
+    @Test
+    void runsOnNonStringVariablesAlso() {
+        //language=java
+        rewriteRun(
+          java(
+            """
+              class SomeClass {
+                  boolean foo(String str) {
+                      return str.equals(getMessage().toString());
+                  }
+
+                  StringBuilder getMessage() {
+                      return new StringBuilder("message");
+                  }
+              }
+              """,
+            """
+              class SomeClass {
+                  boolean foo(String str) {
+                      return str.contentEquals(getMessage());
+                  }
+
+                  StringBuilder getMessage() {
+                      return new StringBuilder("message");
+                  }
+              }
+              """
+          )
+        );
+    }
+}