AssignmentInSubExpressionCheck.java

/*
 * 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 javax.annotation.Nullable;
import org.sonar.check.Rule;
import org.sonar.java.model.ExpressionUtils;
import org.sonar.plugins.java.api.JavaFileScanner;
import org.sonar.plugins.java.api.JavaFileScannerContext;
import org.sonar.plugins.java.api.tree.AnnotationTree;
import org.sonar.plugins.java.api.tree.AssignmentExpressionTree;
import org.sonar.plugins.java.api.tree.BaseTreeVisitor;
import org.sonar.plugins.java.api.tree.BinaryExpressionTree;
import org.sonar.plugins.java.api.tree.ExpressionStatementTree;
import org.sonar.plugins.java.api.tree.ExpressionTree;
import org.sonar.plugins.java.api.tree.LambdaExpressionTree;
import org.sonar.plugins.java.api.tree.Tree;
import org.sonar.plugins.java.api.tree.Tree.Kind;
import org.sonar.plugins.java.api.tree.VariableTree;
import org.sonar.plugins.java.api.tree.WhileStatementTree;
import org.sonar.plugins.java.api.tree.YieldStatementTree;
import org.sonarsource.analyzer.commons.annotations.DeprecatedRuleKey;

@DeprecatedRuleKey(ruleKey = "AssignmentInSubExpressionCheck", repositoryKey = "squid")
@Rule(key = "S1121")
public class AssignmentInSubExpressionCheck extends BaseTreeVisitor implements JavaFileScanner {

  private JavaFileScannerContext context;

  @Override
  public void scanFile(JavaFileScannerContext context) {
    this.context = context;

    scan(context.getTree());
  }

  @Override
  public void visitAnnotation(AnnotationTree annotationTree) {
    //skip scanning of annotation : assignment in annotation is normal behaviour
    scan(annotationTree.annotationType());
  }

  @Override
  public void visitLambdaExpression(LambdaExpressionTree lambdaExpressionTree) {
    //skip lambda if body is an assignment
    if(!(lambdaExpressionTree.body() instanceof AssignmentExpressionTree)) {
      super.visitLambdaExpression(lambdaExpressionTree);
    }
  }

  @Override
  public void visitExpressionStatement(ExpressionStatementTree tree) {
    ExpressionTree expressionTree = ExpressionUtils.skipParentheses(tree.expression());
    expressionTree = skipChainedAssignments(expressionTree);
    scan(expressionTree);
  }

  private ExpressionTree skipChainedAssignments(ExpressionTree expressionTree) {
    ExpressionTree tree = ExpressionUtils.skipParentheses(expressionTree);
    while (tree instanceof AssignmentExpressionTree assignmentExpressionTree) {
      scan(assignmentExpressionTree.variable());
      tree = ExpressionUtils.skipParentheses(assignmentExpressionTree.expression());
    }
    return tree;
  }

  @Override
  public void visitBinaryExpression(BinaryExpressionTree tree) {
    if (isRelationalExpression(tree)) {
      visitInnerExpression(tree.leftOperand());
      visitInnerExpression(tree.rightOperand());
    } else {
      super.visitBinaryExpression(tree);
    }
  }

  private void visitInnerExpression(ExpressionTree tree) {
    AssignmentExpressionTree assignmentExpressionTree = getInnerAssignmentExpression(tree);
    if (assignmentExpressionTree != null) {
      super.visitAssignmentExpression(assignmentExpressionTree);
    } else {
      scan(tree);
    }
  }

  @Nullable
  private static AssignmentExpressionTree getInnerAssignmentExpression(ExpressionTree tree) {
    ExpressionTree expressionTree = ExpressionUtils.skipParentheses(tree);
    if (expressionTree.is(Kind.ASSIGNMENT)) {
      return (AssignmentExpressionTree) expressionTree;
    }
    return null;
  }

  private static boolean isRelationalExpression(Tree tree) {
    return tree.is(
      Kind.EQUAL_TO,
      Kind.NOT_EQUAL_TO,
      Kind.LESS_THAN,
      Kind.LESS_THAN_OR_EQUAL_TO,
      Kind.GREATER_THAN,
      Kind.GREATER_THAN_OR_EQUAL_TO);
  }

  @Override
  public void visitWhileStatement(WhileStatementTree tree) {
    scan(tree.statement());
  }

  @Override
  public void visitVariable(VariableTree tree) {
    ExpressionTree initializer = tree.initializer();
    if (initializer != null) {
      ExpressionTree expressionTree = skipChainedAssignments(initializer);
      scan(expressionTree);
    }
  }

  @Override
  public void visitYieldStatement(YieldStatementTree tree) {
    if (isWithinSwitchExpression(tree)) {
      super.visitYieldStatement(tree);
    }
  }

  private static boolean isWithinSwitchExpression(YieldStatementTree tree) {
    Tree parent = tree.parent();
    while (!parent.is(Tree.Kind.SWITCH_EXPRESSION, Tree.Kind.SWITCH_STATEMENT, Kind.COMPILATION_UNIT)) {
      parent = parent.parent();
    }
    return parent.is(Tree.Kind.SWITCH_EXPRESSION);
  }

  @Override
  public void visitAssignmentExpression(AssignmentExpressionTree tree) {
    super.visitAssignmentExpression(tree);
    context.reportIssue(this, tree.operatorToken(), "Extract the assignment out of this expression.");
  }

}