SONARJAVA-7161 Implement rule S9434 - Qualified "this" should not be used when the unqualified form is enough

its/ruling/src/test/resources/expected/eclipse-jetty-similar-to-main/java-S9434.json

@@ -0,0 +1,9 @@
+{
+"eclipse-jetty:jetty-io/src/main/java/org/eclipse/jetty/io/ssl/SslConnection.java": [
+371,
+380
+],
+"eclipse-jetty:jetty-server/src/main/java/org/eclipse/jetty/server/HttpChannel.java": [
+370
+]
+}

its/ruling/src/test/resources/expected/eclipse-jetty/java-S9434.json

@@ -0,0 +1,20 @@
+{
+"eclipse-jetty:jetty-io/src/main/java/org/eclipse/jetty/io/ssl/SslConnection.java": [
+371,
+380
+],
+"eclipse-jetty:jetty-server/src/main/java/org/eclipse/jetty/server/HttpChannel.java": [
+370
+],
+"eclipse-jetty:jetty-util/src/main/java/org/eclipse/jetty/util/RolloverFileOutputStream.java": [
+410,
+411,
+412
+],
+"eclipse-jetty:jetty-util/src/main/java/org/eclipse/jetty/util/ssl/SslSelectionDump.java": [
+46
+],
+"eclipse-jetty:jetty-util/src/main/java/org/eclipse/jetty/util/thread/ScheduledExecutorScheduler.java": [
+99
+]
+}

its/ruling/src/test/resources/expected/guava/java-S9434.json

@@ -0,0 +1,5 @@
+{
+"guava:src/com/google/common/collect/TreeRangeMap.java": [
+547
+]
+}

java-checks-test-sources/default/src/main/java/checks/RedundantQualifiedThisCheckSample.java

@@ -0,0 +1,174 @@
+package checks;
+
+import java.util.function.Supplier;
+
+public class RedundantQualifiedThisCheckSample {
+
+  private final String id = "id";
+  private int counter;
+
+  String redundantInMethod() {
+    return RedundantQualifiedThisCheckSample.this.id; // Noncompliant {{Remove this redundant qualifier.}} [[quickfixes=qf1]]
+//         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    // fix@qf1 {{Remove the redundant qualifier}}
+    // edit@qf1 [[sc=12;ec=46]] {{}}
+  }
+
+  void redundantOnMethodCall() {
+    RedundantQualifiedThisCheckSample.this.increment(); // Noncompliant [[quickfixes=qf2]]
+//  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    // fix@qf2 {{Remove the redundant qualifier}}
+    // edit@qf2 [[sc=5;ec=39]] {{}}
+  }
+
+  RedundantQualifiedThisCheckSample redundantWithoutMemberAccess() {
+    return RedundantQualifiedThisCheckSample.this; // Noncompliant [[quickfixes=qf3]]
+//         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    // fix@qf3 {{Remove the redundant qualifier}}
+    // edit@qf3 [[sc=12;ec=46]] {{}}
+  }
+
+  Supplier<String> redundantInLambda() {
+    return () -> RedundantQualifiedThisCheckSample.this.id; // Noncompliant [[quickfixes=qf4]]
+//               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    // fix@qf4 {{Remove the redundant qualifier}}
+    // edit@qf4 [[sc=18;ec=52]] {{}}
+  }
+
+  Supplier<Supplier<String>> redundantInNestedLambda() {
+    return () -> () -> RedundantQualifiedThisCheckSample.this.id; // Noncompliant [[quickfixes=qf5]]
+//                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    // fix@qf5 {{Remove the redundant qualifier}}
+    // edit@qf5 [[sc=24;ec=58]] {{}}
+  }
+
+  void increment() {
+    counter++;
+  }
+
+  String compliantExplicitThis() {
+    return this.id;
+  }
+
+  String compliantImplicitThis() {
+    return id;
+  }
+
+  class Inner {
+    private final String id = "inner";
+
+    String outerQualifierIsRequired() {
+      return RedundantQualifiedThisCheckSample.this.id;
+    }
+
+    String ownQualifierIsRedundant() {
+      return Inner.this.id; // Noncompliant [[quickfixes=qf6]]
+//           ^^^^^^^^^^
+      // fix@qf6 {{Remove the redundant qualifier}}
+      // edit@qf6 [[sc=14;ec=20]] {{}}
+    }
+
+    Supplier<String> outerQualifierIsRequiredInLambda() {
+      return () -> RedundantQualifiedThisCheckSample.this.id;
+    }
+
+    Supplier<String> ownQualifierIsRedundantInLambda() {
+      return () -> Inner.this.id; // Noncompliant [[quickfixes=qf7]]
+//                 ^^^^^^^^^^
+      // fix@qf7 {{Remove the redundant qualifier}}
+      // edit@qf7 [[sc=20;ec=26]] {{}}
+    }
+
+    class Innermost {
+      String enclosingQualifiersAreRequired() {
+        return RedundantQualifiedThisCheckSample.this.id + Inner.this.id;
+      }
+
+      String ownQualifierIsRedundant() {
+        return Innermost.this.toString(); // Noncompliant [[quickfixes=qf8]]
+//             ^^^^^^^^^^^^^^
+        // fix@qf8 {{Remove the redundant qualifier}}
+        // edit@qf8 [[sc=16;ec=26]] {{}}
+      }
+    }
+  }
+
+  Supplier<String> anonymousClassNeedsQualifier() {
+    return new Supplier<String>() {
+      @Override
+      public String get() {
+        return RedundantQualifiedThisCheckSample.this.id;
+      }
+    };
+  }
+
+  Supplier<String> lambdaInAnonymousClassNeedsQualifier() {
+    return new Supplier<String>() {
+      @Override
+      public String get() {
+        Supplier<String> nested = () -> RedundantQualifiedThisCheckSample.this.id;
+        return nested.get();
+      }
+    };
+  }
+
+  String localClassNeedsQualifier() {
+    class Local {
+      String get() {
+        return RedundantQualifiedThisCheckSample.this.id;
+      }
+    }
+    return new Local().get();
+  }
+
+  String localClassOwnQualifierIsRedundant() {
+    class Local {
+      String get() {
+        return Local.this.toString(); // Noncompliant [[quickfixes=qf9]]
+//             ^^^^^^^^^^
+        // fix@qf9 {{Remove the redundant qualifier}}
+        // edit@qf9 [[sc=16;ec=22]] {{}}
+      }
+    }
+    return new Local().get();
+  }
+
+  static class StaticNested {
+    private final String id = "nested";
+
+    String ownQualifierIsRedundant() {
+      return StaticNested.this.id; // Noncompliant [[quickfixes=qf10]]
+//           ^^^^^^^^^^^^^^^^^
+      // fix@qf10 {{Remove the redundant qualifier}}
+      // edit@qf10 [[sc=14;ec=27]] {{}}
+    }
+
+    Supplier<String> ownQualifierIsRedundantInLambda() {
+      return () -> StaticNested.this.id; // Noncompliant [[quickfixes=qf11]]
+//                 ^^^^^^^^^^^^^^^^^
+      // fix@qf11 {{Remove the redundant qualifier}}
+      // edit@qf11 [[sc=20;ec=33]] {{}}
+    }
+  }
+
+  enum Status {
+    OPEN;
+
+    String ownQualifierIsRedundant() {
+      return Status.this.name(); // Noncompliant [[quickfixes=qf12]]
+//           ^^^^^^^^^^^
+      // fix@qf12 {{Remove the redundant qualifier}}
+      // edit@qf12 [[sc=14;ec=21]] {{}}
+    }
+  }
+
+  record Point(int x, int y) {
+    int ownQualifierIsRedundant() {
+      return Point.this.x; // Noncompliant [[quickfixes=qf13]]
+//           ^^^^^^^^^^
+      // fix@qf13 {{Remove the redundant qualifier}}
+      // edit@qf13 [[sc=14;ec=20]] {{}}
+    }
+  }
+}
+

java-checks/src/main/java/org/sonar/java/checks/RedundantQualifiedThisCheck.java

@@ -0,0 +1,81 @@
+/*
+ * SonarQube Java
+ * Copyright (C) SonarSource Sàrl
+ * mailto:info AT sonarsource DOT com
+ *
+ * You can redistribute and/or modify this program under the terms of
+ * the Sonar Source-Available License Version 1, as published by SonarSource Sàrl.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the Sonar Source-Available License for more details.
+ *
+ * You should have received a copy of the Sonar Source-Available License
+ * along with this program; if not, see https://sonarsource.com/license/ssal/
+ */
+package org.sonar.java.checks;
+
+import java.util.List;
+import javax.annotation.CheckForNull;
+import org.sonar.check.Rule;
+import org.sonar.java.checks.helpers.QuickFixHelper;
+import org.sonar.java.model.ExpressionUtils;
+import org.sonar.java.reporting.JavaQuickFix;
+import org.sonar.java.reporting.JavaTextEdit;
+import org.sonar.plugins.java.api.IssuableSubscriptionVisitor;
+import org.sonar.plugins.java.api.semantic.Symbol;
+import org.sonar.plugins.java.api.tree.ClassTree;
+import org.sonar.plugins.java.api.tree.MemberSelectExpressionTree;
+import org.sonar.plugins.java.api.tree.Tree;
+
+@Rule(key = "S9434")
+public class RedundantQualifiedThisCheck extends IssuableSubscriptionVisitor {
+
+  private static final String MESSAGE = "Remove this redundant qualifier.";
+
+  @Override
+  public List<Tree.Kind> nodesToVisit() {
+    return List.of(Tree.Kind.MEMBER_SELECT);
+  }
+
+  @Override
+  public void visitNode(Tree tree) {
+    MemberSelectExpressionTree memberSelect = (MemberSelectExpressionTree) tree;
+    if (!ExpressionUtils.isThis(memberSelect.identifier())) {
+      return;
+    }
+    Symbol qualifier = memberSelect.expression().symbolType().symbol();
+    if (!qualifier.isUnknown() && qualifier.equals(innermostEnclosingClass(memberSelect))) {
+      QuickFixHelper.newIssue(context)
+        .forRule(this)
+        .onTree(memberSelect)
+        .withMessage(MESSAGE)
+        .withQuickFix(() -> removeQualifier(memberSelect))
+        .report();
+    }
+  }
+
+  private static JavaQuickFix removeQualifier(MemberSelectExpressionTree memberSelect) {
+    return JavaQuickFix.newQuickFix("Remove the redundant qualifier")
+      .addTextEdit(JavaTextEdit.removeBetweenTree(memberSelect.expression(), memberSelect.operatorToken()))
+      .build();
+  }
+
+  /**
+   * Returns the symbol of the class whose instance an unqualified {@code this} would denote at the given position.
+   * Lambda bodies are transparent because a lambda does not introduce its own {@code this}, while anonymous and
+   * local classes do and are therefore returned like any other class.
+   */
+  @CheckForNull
+  private static Symbol innermostEnclosingClass(Tree tree) {
+    Tree parent = tree.parent();
+    while (parent != null) {
+      if (parent instanceof ClassTree classTree) {
+        return classTree.symbol();
+      }
+      parent = parent.parent();
+    }
+    return null;
+  }
+}

java-checks/src/test/java/org/sonar/java/checks/RedundantQualifiedThisCheckTest.java

@@ -0,0 +1,45 @@
+/*
+ * SonarQube Java
+ * Copyright (C) SonarSource Sàrl
+ * mailto:info AT sonarsource DOT com
+ *
+ * You can redistribute and/or modify this program under the terms of
+ * the Sonar Source-Available License Version 1, as published by SonarSource Sàrl.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the Sonar Source-Available License for more details.
+ *
+ * You should have received a copy of the Sonar Source-Available License
+ * along with this program; if not, see https://sonarsource.com/license/ssal/
+ */
+package org.sonar.java.checks;
+
+import org.junit.jupiter.api.Test;
+import org.sonar.java.checks.verifier.CheckVerifier;
+
+import static org.sonar.java.checks.verifier.TestUtils.mainCodeSourcesPath;
+
+class RedundantQualifiedThisCheckTest {
+
+  private static final String SAMPLE = "checks/RedundantQualifiedThisCheckSample.java";
+  private static final RedundantQualifiedThisCheck CHECK = new RedundantQualifiedThisCheck();
+
+  @Test
+  void test() {
+    CheckVerifier.newVerifier()
+      .onFile(mainCodeSourcesPath(SAMPLE))
+      .withCheck(CHECK)
+      .verifyIssues();
+  }
+
+  @Test
+  void test_without_semantic() {
+    CheckVerifier.newVerifier()
+      .onFile(mainCodeSourcesPath(SAMPLE))
+      .withCheck(CHECK)
+      .withoutSemantic()
+      .verifyIssues();
+  }
+}