/*
* SonarQube Java
* Copyright (C) 2012-2016 SonarSource SA
* mailto:contact AT sonarsource DOT com
*
* 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 02110-1301, USA.
*/
package org.sonar.java.checks;
import org.sonar.check.Rule;
import org.sonar.java.JavaVersionAwareVisitor;
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.JavaVersion;
import org.sonar.plugins.java.api.tree.Arguments;
import org.sonar.plugins.java.api.tree.BaseTreeVisitor;
import org.sonar.plugins.java.api.tree.BinaryExpressionTree;
import org.sonar.plugins.java.api.tree.BlockTree;
import org.sonar.plugins.java.api.tree.ExpressionStatementTree;
import org.sonar.plugins.java.api.tree.ExpressionTree;
import org.sonar.plugins.java.api.tree.IdentifierTree;
import org.sonar.plugins.java.api.tree.LambdaExpressionTree;
import org.sonar.plugins.java.api.tree.MemberSelectExpressionTree;
import org.sonar.plugins.java.api.tree.MethodInvocationTree;
import org.sonar.plugins.java.api.tree.NewClassTree;
import org.sonar.plugins.java.api.tree.ParenthesizedTree;
import org.sonar.plugins.java.api.tree.ReturnStatementTree;
import org.sonar.plugins.java.api.tree.Tree;
import org.sonar.plugins.java.api.tree.VariableTree;
import javax.annotation.Nullable;
import java.util.List;
import java.util.Optional;
import java.util.stream.IntStream;
@Rule(key = "S1612")
public class ReplaceLambdaByMethodRefCheck extends BaseTreeVisitor implements JavaFileScanner, JavaVersionAwareVisitor {
private JavaFileScannerContext context;
@Override
public boolean isCompatibleWithJavaVersion(JavaVersion version) {
return version.isJava8Compatible();
}
@Override
public void scanFile(JavaFileScannerContext context) {
this.context = context;
if (context.getSemanticModel() != null) {
scan(context.getTree());
}
}
@Override
public void visitLambdaExpression(LambdaExpressionTree tree) {
if (isReplaceableSingleMethodInvocation(tree) || isBodyBlockInvokingMethod(tree)) {
context.reportIssue(this, tree.arrowToken(), "Replace this lambda with a method reference." + context.getJavaVersion().java8CompatibilityMessage());
} else {
getNullCheck(tree)
.ifPresent(nullMethod ->
context.reportIssue(this, tree.arrowToken(),
"Replace this lambda with method reference 'Objects::" + nullMethod + "'." + context.getJavaVersion().java8CompatibilityMessage())
);
}
super.visitLambdaExpression(tree);
}
private static Optional<String> getNullCheck(LambdaExpressionTree lambda) {
Tree lambdaBody = lambda.body();
if (isBlockWithOneStatement(lambdaBody)) {
return getNullCheckFromReturn(((BlockTree) lambdaBody).body().get(0), lambda);
}
return getNullCheck(lambdaBody, lambda);
}
private static Optional<String> getNullCheckFromReturn(Tree statement, LambdaExpressionTree lambda) {
if (statement.is(Tree.Kind.RETURN_STATEMENT)) {
return getNullCheck(((ReturnStatementTree) statement).expression(), lambda);
}
return Optional.empty();
}
private static Optional<String> getNullCheck(@Nullable Tree statement, LambdaExpressionTree tree) {
if (statement == null) {
return Optional.empty();
}
Tree expr = statement;
if (expr.is(Tree.Kind.PARENTHESIZED_EXPRESSION)) {
expr = ExpressionUtils.skipParentheses((ParenthesizedTree) statement);
}
if (expr.is(Tree.Kind.EQUAL_TO, Tree.Kind.NOT_EQUAL_TO)) {
BinaryExpressionTree bet = (BinaryExpressionTree) expr;
ExpressionTree leftOperand = ExpressionUtils.skipParentheses(bet.leftOperand());
ExpressionTree rightOperand = ExpressionUtils.skipParentheses(bet.rightOperand());
if (nullAgainstParam(leftOperand, rightOperand, tree) || nullAgainstParam(rightOperand, leftOperand, tree)) {
return Optional.of(expr.is(Tree.Kind.EQUAL_TO) ? "isNull" : "nonNull");
}
}
return Optional.empty();
}
private static boolean nullAgainstParam(ExpressionTree o1, ExpressionTree o2, LambdaExpressionTree tree) {
if (o1.is(Tree.Kind.NULL_LITERAL) && o2.is(Tree.Kind.IDENTIFIER)) {
List<VariableTree> parameters = tree.parameters();
return parameters.size() == 1 && parameters.get(0).symbol().equals(((IdentifierTree) o2).symbol());
}
return false;
}
private static boolean isReplaceableSingleMethodInvocation(LambdaExpressionTree lambdaTree) {
return isMethodInvocation(lambdaTree.body(), lambdaTree);
}
private static boolean isBodyBlockInvokingMethod(LambdaExpressionTree lambdaTree) {
Tree lambdaBody = lambdaTree.body();
if (isBlockWithOneStatement(lambdaBody)) {
Tree statement = ((BlockTree) lambdaBody).body().get(0);
return isExpressionStatementInvokingMethod(statement, lambdaTree) || isReturnStatementInvokingMethod(statement, lambdaTree);
}
return false;
}
private static boolean isBlockWithOneStatement(Tree tree) {
return tree.is(Tree.Kind.BLOCK) && ((BlockTree) tree).body().size() == 1;
}
private static boolean isExpressionStatementInvokingMethod(Tree statement, LambdaExpressionTree lambdaTree) {
return statement.is(Tree.Kind.EXPRESSION_STATEMENT) && isMethodInvocation(((ExpressionStatementTree) statement).expression(), lambdaTree);
}
private static boolean isReturnStatementInvokingMethod(Tree statement, LambdaExpressionTree lambdaTree) {
return statement.is(Tree.Kind.RETURN_STATEMENT) && isMethodInvocation(((ReturnStatementTree) statement).expression(), lambdaTree);
}
private static boolean isMethodInvocation(@Nullable Tree tree, LambdaExpressionTree lambdaTree) {
if (tree != null && tree.is(Tree.Kind.METHOD_INVOCATION, Tree.Kind.NEW_CLASS)) {
Arguments arguments;
if(tree.is(Tree.Kind.NEW_CLASS)) {
if(((NewClassTree) tree).classBody() != null) {
return false;
}
arguments = ((NewClassTree) tree).arguments();
} else {
arguments = ((MethodInvocationTree) tree).arguments();
}
List<VariableTree> parameters = lambdaTree.parameters();
return matchingParameters(parameters, arguments) || (arguments.isEmpty() && isNoArgMethodInvocationFromLambdaParam(tree, parameters));
}
return false;
}
private static boolean matchingParameters(List<VariableTree> parameters, Arguments arguments) {
return arguments.size() == parameters.size() &&
IntStream.range(0, arguments.size()).allMatch(i -> {
List<IdentifierTree> usages = parameters.get(i).symbol().usages();
return usages.size() == 1 && usages.get(0).equals(arguments.get(i));
});
}
private static boolean isNoArgMethodInvocationFromLambdaParam(Tree tree, List<VariableTree> parameters) {
if (!tree.is(Tree.Kind.METHOD_INVOCATION) || parameters.size() != 1) {
return false;
}
ExpressionTree methodSelect = ((MethodInvocationTree) tree).methodSelect();
if (methodSelect.is(Tree.Kind.MEMBER_SELECT)) {
ExpressionTree expression = ((MemberSelectExpressionTree) methodSelect).expression();
return expression.is(Tree.Kind.IDENTIFIER) && parameters.get(0).symbol().equals(((IdentifierTree) expression).symbol());
}
return false;
}
}