org.sonar.java.checks.StringConcatenationInLoopCheck Maven / Gradle / Ivy

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/*
 * SonarQube Java
 * Copyright (C) 2012 SonarSource
 * [email protected]
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 3 of the License, or (at your option) any later version.
 *
 * 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 GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02
 */
package org.sonar.java.checks;

import org.sonar.api.rule.RuleKey;
import org.sonar.check.Priority;
import org.sonar.check.Rule;
import org.sonar.java.model.SyntacticEquivalence;
import org.sonar.java.model.expression.AssignmentExpressionTreeImpl;
import org.sonar.java.resolve.SemanticModel;
import org.sonar.java.resolve.Symbol;
import org.sonar.java.resolve.Type;
import org.sonar.plugins.java.api.JavaFileScanner;
import org.sonar.plugins.java.api.JavaFileScannerContext;
import org.sonar.plugins.java.api.tree.ArrayAccessExpressionTree;
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.DoWhileStatementTree;
import org.sonar.plugins.java.api.tree.ExpressionTree;
import org.sonar.plugins.java.api.tree.ForEachStatement;
import org.sonar.plugins.java.api.tree.ForStatementTree;
import org.sonar.plugins.java.api.tree.IdentifierTree;
import org.sonar.plugins.java.api.tree.MemberSelectExpressionTree;
import org.sonar.plugins.java.api.tree.MethodInvocationTree;
import org.sonar.plugins.java.api.tree.ParenthesizedTree;
import org.sonar.plugins.java.api.tree.Tree;
import org.sonar.plugins.java.api.tree.WhileStatementTree;

import java.util.Deque;
import java.util.LinkedList;

@Rule(
    key = StringConcatenationInLoopCheck.RULE_KEY,
    priority = Priority.MAJOR,
    tags = {"performance"})
public class StringConcatenationInLoopCheck extends BaseTreeVisitor implements JavaFileScanner {

  public static final String RULE_KEY = "S1643";
  private final RuleKey ruleKey = RuleKey.of(CheckList.REPOSITORY_KEY, RULE_KEY);

  private JavaFileScannerContext context;
  private Deque loopLevel = new LinkedList();
  private SemanticModel semanticModel;

  @Override
  public void scanFile(JavaFileScannerContext context) {
    this.context = context;
    loopLevel.clear();
    semanticModel = (SemanticModel) context.getSemanticModel();
    scan(context.getTree());
  }


  @Override
  public void visitAssignmentExpression(AssignmentExpressionTree tree) {
    if (!loopLevel.isEmpty() && isStringConcatenation(tree) && isNotLoopLocalVar(tree)) {
      context.addIssue(tree, ruleKey, "Use a StringBuilder instead.");
    }
    super.visitAssignmentExpression(tree);
  }

  private boolean isNotLoopLocalVar(AssignmentExpressionTree tree) {
    IdentifierTree idTree = getIdentifierTree(tree.variable());
    Tree envTree = semanticModel.getTree(semanticModel.getEnv(semanticModel.getReference(idTree)));
    Tree loopTree = loopLevel.peek();
    if(envTree!= null && (envTree.equals(loopTree) || envTree.equals(loopStatement(loopTree)))) {
      return false;
    }
    return true;
  }

  private IdentifierTree getIdentifierTree(ExpressionTree tree) {
    IdentifierTree idTree;
    if(tree.is(Tree.Kind.MEMBER_SELECT)) {
      idTree = getIdentifierTree(((MemberSelectExpressionTree) tree).expression());
    } else if(tree.is(Tree.Kind.ARRAY_ACCESS_EXPRESSION)){
      idTree = getIdentifierTree(((ArrayAccessExpressionTree)tree).expression());
    } else if(tree.is(Tree.Kind.METHOD_INVOCATION)){
      idTree = getIdentifierTree(((MethodInvocationTree) tree).methodSelect());
    } else {
      idTree = (IdentifierTree)tree;
    }
    return idTree;
  }

  private Tree loopStatement(Tree loopTree) {
    if(loopTree.is(Tree.Kind.FOR_STATEMENT)) {
      return ((ForStatementTree) loopTree).statement();
    } else if(loopTree.is(Tree.Kind.DO_STATEMENT)) {
      return ((DoWhileStatementTree) loopTree).statement();
    } else if(loopTree.is(Tree.Kind.WHILE_STATEMENT)) {
      return ((WhileStatementTree) loopTree).statement();
    } else if(loopTree.is(Tree.Kind.FOR_EACH_STATEMENT)) {
      return ((ForEachStatement) loopTree).statement();
    }
    return null;
  }

  private boolean isStringConcatenation(AssignmentExpressionTree tree) {
    return isString(((AssignmentExpressionTreeImpl) tree).getSymbolType()) && isConcatenation(tree);
  }

  private boolean isConcatenation(AssignmentExpressionTree tree) {
    return tree.is(Tree.Kind.PLUS_ASSIGNMENT) || (tree.is(Tree.Kind.ASSIGNMENT) && removeParenthesis(tree.expression()).is(Tree.Kind.PLUS)
      && concatenateVariable(tree.variable(), (BinaryExpressionTree) removeParenthesis(tree.expression()))
    );
  }

  private boolean concatenateVariable(ExpressionTree variable, BinaryExpressionTree plus) {
    return concatenateVariable(variable, plus.leftOperand()) || concatenateVariable(variable, plus.rightOperand());
  }

  private boolean concatenateVariable(ExpressionTree variable, ExpressionTree operand) {
    if(operand.is(Tree.Kind.PLUS)) {
      return concatenateVariable(variable, (BinaryExpressionTree) operand);
    }
    return SyntacticEquivalence.areEquivalent(variable, operand);
  }

  private Tree removeParenthesis(Tree tree) {
    Tree result = tree;
    while(result.is(Tree.Kind.PARENTHESIZED_EXPRESSION)) {
      result = ((ParenthesizedTree) result).expression();
    }
    return result;
  }

  private boolean isString(Type type) {
    if (type.isTagged(Type.CLASS)) {
      Symbol.TypeSymbol typeSymbol = ((Type.ClassType) type).getSymbol();
      return "String".equals(typeSymbol.getName()) && "java.lang".equals(typeSymbol.owner().getName());
    }
    return false;
  }

  @Override
  public void visitForEachStatement(ForEachStatement tree) {
    loopLevel.push(tree);
    super.visitForEachStatement(tree);
    loopLevel.pop();
  }

  @Override
  public void visitForStatement(ForStatementTree tree) {
    loopLevel.push(tree);
    super.visitForStatement(tree);
    loopLevel.pop();
  }

  @Override
  public void visitWhileStatement(WhileStatementTree tree) {
    loopLevel.push(tree);
    super.visitWhileStatement(tree);
    loopLevel.pop();
  }

  @Override
  public void visitDoWhileStatement(DoWhileStatementTree tree) {
    loopLevel.push(tree);
    super.visitDoWhileStatement(tree);
    loopLevel.pop();
  }


}