net.sourceforge.pmd.rules.UselessOperationOnImmutable Maven / Gradle / Ivy

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package net.sourceforge.pmd.rules;

import java.util.Iterator;
import java.util.List;
import java.util.Set;

import net.sourceforge.pmd.AbstractRule;
import net.sourceforge.pmd.ast.ASTConditionalExpression;
import net.sourceforge.pmd.ast.ASTExpression;
import net.sourceforge.pmd.ast.ASTLocalVariableDeclaration;
import net.sourceforge.pmd.ast.ASTPrimaryExpression;
import net.sourceforge.pmd.ast.ASTPrimarySuffix;
import net.sourceforge.pmd.ast.ASTType;
import net.sourceforge.pmd.ast.ASTVariableDeclaratorId;
import net.sourceforge.pmd.ast.Node;
import net.sourceforge.pmd.ast.SimpleNode;
import net.sourceforge.pmd.symboltable.NameOccurrence;
import net.sourceforge.pmd.util.CollectionUtil;

/**
 * An operation on an Immutable object (BigDecimal or BigInteger) won't change
 * the object itself. The result of the operation is a new object. Therefore,
 * ignoring the operation result is an error.
 */
public class UselessOperationOnImmutable extends AbstractRule {
    /**
     * These are the methods which are immutable
     */
    private static final Set targetMethods = CollectionUtil.asSet(new String[] { ".add", ".multiply", ".divide", ".subtract", ".setScale", ".negate", ".movePointLeft", ".movePointRight", ".pow", ".shiftLeft", ".shiftRight" });

    /**
     * These are the classes that the rule can apply to
     */
    private static final Set targetClasses = CollectionUtil.asSet(new String[] { "java.math.BigDecimal", "BigDecimal", "java.math.BigInteger", "BigInteger" });

    public Object visit(ASTLocalVariableDeclaration node, Object data) {

        ASTVariableDeclaratorId var = getDeclaration(node);
        if (var == null) {
            return super.visit(node, data);
        }
        String variableName = var.getImage();
        for (NameOccurrence no: var.getUsages()) {
            // FIXME - getUsages will return everything with the same name as the variable, 
            // see JUnit test, case 6. Changing to SimpleNode below, revisit when getUsages is fixed
            SimpleNode sn = no.getLocation();
            Node primaryExpression = sn.jjtGetParent().jjtGetParent();
			Class parentClass = primaryExpression.jjtGetParent().getClass();
            if (!(parentClass.equals(ASTExpression.class) || parentClass.equals(ASTConditionalExpression.class) || 
            		hasComparisons(primaryExpression))) {
                String methodCall = sn.getImage().substring(variableName.length());
                if (targetMethods.contains(methodCall)) {
                    addViolation(data, sn);
                }
            }
        }
        return super.visit(node, data);
    }

    /**
     * Check whether the Immutable is compareTo'd something
     */
	private boolean hasComparisons(Node primaryExpression) {
		if (primaryExpression.getClass().equals(ASTPrimaryExpression.class)) {
			List suffixes = ((ASTPrimaryExpression)primaryExpression).findChildrenOfType(ASTPrimarySuffix.class);
			for (Iterator iterator = suffixes.iterator(); iterator.hasNext();) {
				ASTPrimarySuffix suffix = iterator.next();
				if ("compareTo".equals(suffix.getImage()))
					return true;
			}
		} else {
			//Some weird usage of the Immutable
		}
		return false;	//No comparison
	}

    /**
     * This method checks the variable declaration if it is on a class we care
     * about. If it is, it returns the DeclaratorId
     * 
     * @param node
     *            The ASTLocalVariableDeclaration which is a problem
     * @return ASTVariableDeclaratorId
     */
    private ASTVariableDeclaratorId getDeclaration(ASTLocalVariableDeclaration node) {
        ASTType type = node.getTypeNode();
        if (targetClasses.contains(type.getTypeImage())) {
            return (ASTVariableDeclaratorId) node.jjtGetChild(1).jjtGetChild(0);
        }
        return null;
    }
}