/*
* Copyright 2000-2014 JetBrains s.r.o.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.intellij.codeInsight.daemon.impl.quickfix;
import com.intellij.psi.*;
import com.intellij.psi.util.PsiUtil;
import com.intellij.util.IncorrectOperationException;
import com.siyeh.ig.psiutils.SideEffectChecker;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;
import java.util.ArrayList;
import java.util.List;
public class RemoveUnusedVariableUtil {
public enum RemoveMode {
MAKE_STATEMENT,
DELETE_ALL,
CANCEL
}
public static boolean checkSideEffects(PsiExpression element, @Nullable PsiVariable variableToIgnore, List<PsiElement> sideEffects) {
if (sideEffects == null || element == null) return false;
List<PsiElement> writes = new ArrayList<>();
SideEffectChecker.checkSideEffects(element, writes);
if (variableToIgnore != null) {
for (int i = writes.size() - 1; i >= 0; i--) {
PsiElement write = writes.get(i);
if (!(write instanceof PsiAssignmentExpression)) continue;
PsiExpression lExpression = ((PsiAssignmentExpression)write).getLExpression();
if (lExpression instanceof PsiReference && ((PsiReference)lExpression).resolve() == variableToIgnore) {
writes.remove(i);
}
}
}
sideEffects.addAll(writes);
return !writes.isEmpty();
}
static PsiElement replaceElementWithExpression(PsiExpression expression,
PsiElementFactory factory,
PsiElement element) throws IncorrectOperationException {
PsiElement elementToReplace = element;
PsiElement expressionToReplaceWith = expression;
if (element.getParent() instanceof PsiExpressionStatement) {
elementToReplace = element.getParent();
expressionToReplaceWith =
factory.createStatementFromText((expression == null ? "" : expression.getText()) + ";", null);
}
else if (element.getParent() instanceof PsiDeclarationStatement) {
expressionToReplaceWith =
factory.createStatementFromText((expression == null ? "" : expression.getText()) + ";", null);
}
return elementToReplace.replace(expressionToReplaceWith);
}
static PsiElement createStatementIfNeeded(PsiExpression expression,
PsiElementFactory factory,
PsiElement element) throws IncorrectOperationException {
// if element used in expression, subexpression will do
if (!(element.getParent() instanceof PsiExpressionStatement) &&
!(element.getParent() instanceof PsiDeclarationStatement)) {
return expression;
}
return factory.createStatementFromText((expression == null ? "" : expression.getText()) + ";", null);
}
static void deleteWholeStatement(PsiElement element, PsiElementFactory factory)
throws IncorrectOperationException {
// just delete it altogether
if (element.getParent() instanceof PsiExpressionStatement) {
PsiExpressionStatement parent = (PsiExpressionStatement)element.getParent();
if (parent.getParent() instanceof PsiCodeBlock) {
parent.delete();
}
else {
// replace with empty statement (to handle with 'if (..) i=0;' )
parent.replace(createStatementIfNeeded(null, factory, element));
}
}
else {
element.delete();
}
}
static void deleteReferences(PsiVariable variable, List<PsiElement> references, @NotNull RemoveMode mode) throws IncorrectOperationException {
for (PsiElement expression : references) {
processUsage(expression, variable, null, mode);
}
}
static void collectReferences(@NotNull PsiElement context, final PsiVariable variable, final List<PsiElement> references) {
context.accept(new JavaRecursiveElementWalkingVisitor() {
@Override public void visitReferenceExpression(PsiReferenceExpression expression) {
if (expression.resolve() == variable) references.add(expression);
super.visitReferenceExpression(expression);
}
});
}
/**
* @param sideEffects if null, delete usages, otherwise collect side effects
* @return true if there are at least one unrecoverable side effect found, false if no side effects,
* null if read usage found (may happen if interval between fix creation in invoke() call was long enough)
* @throws com.intellij.util.IncorrectOperationException
*/
static Boolean processUsage(PsiElement element, PsiVariable variable, List<PsiElement> sideEffects, @NotNull RemoveMode deleteMode)
throws IncorrectOperationException {
if (!element.isValid()) return null;
PsiElementFactory factory = JavaPsiFacade.getInstance(variable.getProject()).getElementFactory();
while (element != null) {
if (element instanceof PsiAssignmentExpression) {
PsiAssignmentExpression expression = (PsiAssignmentExpression)element;
PsiExpression lExpression = expression.getLExpression();
// there should not be read access to the variable, otherwise it is not unused
if (!(lExpression instanceof PsiReferenceExpression) || variable != ((PsiReferenceExpression)lExpression).resolve()) {
return null;
}
PsiExpression rExpression = expression.getRExpression();
rExpression = PsiUtil.deparenthesizeExpression(rExpression);
if (rExpression == null) return true;
// replace assignment with expression and resimplify
boolean sideEffectFound = checkSideEffects(rExpression, variable, sideEffects);
if (!(element.getParent() instanceof PsiExpressionStatement) || PsiUtil.isStatement(rExpression)) {
if (deleteMode == RemoveMode.MAKE_STATEMENT ||
deleteMode == RemoveMode.DELETE_ALL && !(element.getParent() instanceof PsiExpressionStatement)) {
element = replaceElementWithExpression(rExpression, factory, element);
while (element.getParent() instanceof PsiParenthesizedExpression) {
element = element.getParent().replace(element);
}
List<PsiElement> references = new ArrayList<>();
collectReferences(element, variable, references);
deleteReferences(variable, references, deleteMode);
}
else if (deleteMode == RemoveMode.DELETE_ALL) {
deleteWholeStatement(element, factory);
}
return true;
}
else {
if (deleteMode != RemoveMode.CANCEL) {
deleteWholeStatement(element, factory);
}
return !sideEffectFound;
}
}
else if (element instanceof PsiExpressionStatement && deleteMode != RemoveMode.CANCEL) {
final PsiElement parent = element.getParent();
if (parent instanceof PsiIfStatement || parent instanceof PsiLoopStatement && ((PsiLoopStatement)parent).getBody() == element) {
element.replace(JavaPsiFacade.getElementFactory(element.getProject()).createStatementFromText(";", element));
} else {
element.delete();
}
break;
}
else if (element instanceof PsiVariable && element == variable) {
PsiExpression expression = variable.getInitializer();
if (expression != null) {
expression = PsiUtil.deparenthesizeExpression(expression);
}
boolean sideEffectsFound = checkSideEffects(expression, variable, sideEffects);
if (expression != null && PsiUtil.isStatement(expression) && variable instanceof PsiLocalVariable
&&
!(variable.getParent() instanceof PsiDeclarationStatement &&
((PsiDeclarationStatement)variable.getParent()).getDeclaredElements().length > 1)) {
if (deleteMode == RemoveMode.MAKE_STATEMENT) {
element = element.replace(createStatementIfNeeded(expression, factory, element));
List<PsiElement> references = new ArrayList<>();
collectReferences(element, variable, references);
deleteReferences(variable, references, deleteMode);
}
else if (deleteMode == RemoveMode.DELETE_ALL) {
element.delete();
}
return true;
}
else {
if (deleteMode != RemoveMode.CANCEL) {
if (element instanceof PsiField) {
((PsiField)element).normalizeDeclaration();
}
element.delete();
}
return !sideEffectsFound;
}
}
element = element.getParent();
}
return true;
}
}