plugins/InspectionGadgets/InspectionGadgetsAnalysis/src/com/siyeh/ig/bugs/MismatchedArrayReadWriteInspection.java

/*
 * Copyright 2003-2014 Dave Griffith, Bas Leijdekkers
 *
 * 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.siyeh.ig.bugs;

import com.intellij.codeInsight.daemon.impl.analysis.HighlightUtil;
import com.intellij.psi.*;
import com.intellij.psi.tree.IElementType;
import com.intellij.psi.util.PsiTreeUtil;
import com.intellij.psi.util.PsiUtil;
import com.siyeh.InspectionGadgetsBundle;
import com.siyeh.ig.BaseInspection;
import com.siyeh.ig.BaseInspectionVisitor;
import com.siyeh.ig.psiutils.CloneUtils;
import com.siyeh.ig.psiutils.VariableAccessUtils;
import org.jetbrains.annotations.NonNls;
import org.jetbrains.annotations.NotNull;

public class MismatchedArrayReadWriteInspection extends BaseInspection {

  @Override
  @NotNull
  public String getID() {
    return "MismatchedReadAndWriteOfArray";
  }

  @Override
  @NotNull
  public String getDisplayName() {
    return InspectionGadgetsBundle.message(
      "mismatched.read.write.array.display.name");
  }

  @Override
  @NotNull
  public String buildErrorString(Object... infos) {
    final boolean written = ((Boolean)infos[0]).booleanValue();
    if (written) {
      return InspectionGadgetsBundle.message(
        "mismatched.read.write.array.problem.descriptor.write.not.read");
    }
    else {
      return InspectionGadgetsBundle.message(
        "mismatched.read.write.array.problem.descriptor.read.not.write");
    }
  }

  @Override
  public boolean isEnabledByDefault() {
    return true;
  }

  @Override
  public boolean runForWholeFile() {
    return true;
  }

  @Override
  public BaseInspectionVisitor buildVisitor() {
    return new MismatchedArrayReadWriteVisitor();
  }

  private static class MismatchedArrayReadWriteVisitor extends BaseInspectionVisitor {

    @Override
    public void visitField(@NotNull PsiField field) {
      super.visitField(field);
      if (!field.hasModifierProperty(PsiModifier.PRIVATE)) {
        return;
      }
      if (HighlightUtil.isSerializationImplicitlyUsedField(field)) {
        return;
      }
      final PsiClass containingClass = PsiUtil.getTopLevelClass(field);
      if (!checkVariable(field, containingClass)) {
        return;
      }
      final boolean written = arrayContentsAreWritten(field, containingClass);
      final boolean read = arrayContentsAreRead(field, containingClass);
      if (written == read) {
        return;
      }
      registerFieldError(field, Boolean.valueOf(written));
    }

    @Override
    public void visitLocalVariable(@NotNull PsiLocalVariable variable) {
      super.visitLocalVariable(variable);
      final PsiCodeBlock codeBlock = PsiTreeUtil.getParentOfType(variable, PsiCodeBlock.class);
      if (!checkVariable(variable, codeBlock)) {
        return;
      }
      final boolean written = arrayContentsAreWritten(variable, codeBlock);
      final boolean read = arrayContentsAreRead(variable, codeBlock);
      if (written == read) {
        return;
      }
      registerVariableError(variable, Boolean.valueOf(written));
    }

    private static boolean checkVariable(PsiVariable variable,
                                         PsiElement context) {
      if (context == null) {
        return false;
      }
      final PsiType type = variable.getType();
      if (type.getArrayDimensions() == 0) {
        return false;
      }
      if (VariableAccessUtils.variableIsAssigned(variable, context)) {
        return false;
      }
      if (VariableAccessUtils.variableIsAssignedFrom(variable, context)) {
        return false;
      }
      if (VariableAccessUtils.variableIsReturned(variable, context)) {
        return false;
      }
      return !VariableAccessUtils.variableIsUsedInArrayInitializer(variable, context);
    }

    private static boolean arrayContentsAreWritten(PsiVariable variable,
                                                   PsiElement context) {
      if (VariableAccessUtils.arrayContentsAreAssigned(variable, context)) {
        return true;
      }
      if (!isDefaultArrayInitializer(variable.getInitializer())) {
        return true;
      }
      return variableIsWritten(variable, context);
    }

    private static boolean arrayContentsAreRead(PsiVariable variable,
                                                PsiElement context) {
      if (VariableAccessUtils.arrayContentsAreAccessed(variable, context)) {
        return true;
      }
      if (isPossiblyReferenceThatIsReadLater(variable.getInitializer())) {
        return true;
      }
      return variableIsRead(variable, context);
    }

    private static boolean isPossiblyReferenceThatIsReadLater(PsiExpression initializer) {
      if (initializer == null || initializer instanceof PsiNewExpression || initializer instanceof PsiArrayInitializerExpression) {
        return false;
      }
      if (initializer instanceof PsiMethodCallExpression) {
        final PsiMethodCallExpression methodCallExpression = (PsiMethodCallExpression)initializer;
        final PsiMethod method = methodCallExpression.resolveMethod();
        if (method == null) {
          return true;
        }
        if (CloneUtils.isClone(method)) {
          return false;
        }
        @NonNls final String name = method.getName();
        if (!"copyOf".equals(name) && !"copyOfRange".equals(name)) {
          return true;
        }
        final PsiClass aClass = method.getContainingClass();
        return aClass == null || !CommonClassNames.JAVA_UTIL_ARRAYS.equals(aClass.getQualifiedName());
      }
      return true;
    }

    private static boolean isDefaultArrayInitializer(PsiExpression initializer) {
      if (initializer == null) {
        return true;
      }
      if (initializer instanceof PsiNewExpression) {
        final PsiNewExpression newExpression = (PsiNewExpression)initializer;
        final PsiArrayInitializerExpression arrayInitializer = newExpression.getArrayInitializer();
        return arrayInitializer == null || isDefaultArrayInitializer(arrayInitializer);
      }
      else if (initializer instanceof PsiArrayInitializerExpression) {
        final PsiArrayInitializerExpression arrayInitializerExpression = (PsiArrayInitializerExpression)initializer;
        final PsiExpression[] initializers = arrayInitializerExpression.getInitializers();
        return initializers.length == 0;
      }
      return false;
    }

    public static boolean variableIsWritten(@NotNull PsiVariable variable, @NotNull PsiElement context) {
      final VariableReadWriteVisitor visitor = new VariableReadWriteVisitor(variable, true);
      context.accept(visitor);
      return visitor.isPassed();
    }

    public static boolean variableIsRead(@NotNull PsiVariable variable, @NotNull PsiElement context) {
      final VariableReadWriteVisitor visitor =
        new VariableReadWriteVisitor(variable, false);
      context.accept(visitor);
      return visitor.isPassed();
    }

    static class VariableReadWriteVisitor extends JavaRecursiveElementVisitor {

      @NotNull
      private final PsiVariable variable;
      private final boolean write;
      private boolean passed = false;

      VariableReadWriteVisitor(@NotNull PsiVariable variable, boolean write) {
        this.variable = variable;
        this.write = write;
      }

      @Override
      public void visitElement(@NotNull PsiElement element) {
        if (!passed) {
          super.visitElement(element);
        }
      }

      @Override
      public void visitBinaryExpression(PsiBinaryExpression expression) {
        super.visitBinaryExpression(expression);
        if (write || passed) {
          return;
        }
        final IElementType tokenType = expression.getOperationTokenType();
        if (!JavaTokenType.EQEQ.equals(tokenType) && !JavaTokenType.NE.equals(tokenType)) {
          return;
        }
        final PsiExpression lhs = expression.getLOperand();
        if (!(lhs instanceof PsiBinaryExpression)) {
          if (VariableAccessUtils.mayEvaluateToVariable(lhs, variable)) {
            passed = true;
          }
        }
        final PsiExpression rhs = expression.getROperand();
        if (!(rhs instanceof PsiBinaryExpression)) {
          if (VariableAccessUtils.mayEvaluateToVariable(rhs, variable)) {
            passed = true;
          }
        }
      }

      @Override
      public void visitMethodCallExpression(
        @NotNull PsiMethodCallExpression call) {
        if (passed) {
          return;
        }
        super.visitMethodCallExpression(call);
        final PsiExpressionList argumentList = call.getArgumentList();
        final PsiExpression[] arguments = argumentList.getExpressions();
        for (int i = 0; i < arguments.length; i++) {
          final PsiExpression argument = arguments[i];
          if (VariableAccessUtils.mayEvaluateToVariable(argument, variable)) {
            if (write && i == 0 && isCallToSystemArraycopy(call)) {
              return;
            }
            if (!write && i == 2 && isCallToSystemArraycopy(call)) {
              return;
            }
            passed = true;
          }
        }
      }

      private static boolean isCallToSystemArraycopy(PsiMethodCallExpression call) {
        final PsiReferenceExpression methodExpression = call.getMethodExpression();
        @NonNls final String name = methodExpression.getReferenceName();
        if (!"arraycopy".equals(name)) {
          return false;
        }
        final PsiExpression qualifier = methodExpression.getQualifierExpression();
        if (!(qualifier instanceof PsiReferenceExpression)) {
          return false;
        }
        final PsiReferenceExpression referenceExpression = (PsiReferenceExpression)qualifier;
        final PsiElement element = referenceExpression.resolve();
        if (!(element instanceof PsiClass)) {
          return false;
        }
        return "java.lang.System".equals(((PsiClass)element).getQualifiedName());
      }

      @Override
      public void visitNewExpression(@NotNull PsiNewExpression newExpression) {
        if (passed) {
          return;
        }
        super.visitNewExpression(newExpression);
        visitPsiCall(newExpression);
      }

      @Override
      public void visitEnumConstant(PsiEnumConstant enumConstant) {
        if (passed) {
          return;
        }
        super.visitEnumConstant(enumConstant);
        visitPsiCall(enumConstant);
      }

      private void visitPsiCall(PsiCall newExpression) {
        final PsiExpressionList argumentList = newExpression.getArgumentList();
        if (argumentList == null) {
          return;
        }
        final PsiExpression[] arguments = argumentList.getExpressions();
        for (final PsiExpression argument : arguments) {
          if (VariableAccessUtils.mayEvaluateToVariable(argument, variable)) {
            passed = true;
          }
        }
      }

      public boolean isPassed() {
        return passed;
      }
    }
  }
}