InnerAssignmentCheck.java
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com.puppycrawl.tools.checkstyle.checks.coding |
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Checkstyle |
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These are the metrics that contribute to the Enerjy Score for this file, ranked by impact. So the metrics listed at the top influence the score to a greater extent that the metrics listed at the bottom.
////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code for adherence to a set of rules.
// Copyright (C) 2001-2007 Oliver Burn
//
// This library 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 2.1 of the License, or (at your option) any later version.
//
// This library 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 library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
////////////////////////////////////////////////////////////////////////////////
package com.puppycrawl.tools.checkstyle.checks.coding;
import java.util.Arrays;
import antlr.collections.AST;
import com.puppycrawl.tools.checkstyle.api.Check;
import com.puppycrawl.tools.checkstyle.api.TokenTypes;
import com.puppycrawl.tools.checkstyle.api.DetailAST;
/**
* <p>
* Checks for assignments in subexpressions, such as in
* <code>String s = Integer.toString(i = 2);</code>.
* </p>
* <p>
* Rationale: With the exception of <code>for</code> iterators, all assignments
* should occur in their own toplevel statement to increase readability.
* With inner assignments like the above it is difficult to see all places
* where a variable is set.
* </p>
*
* @author lkuehne
*/
public class InnerAssignmentCheck
extends Check
{
/**
* list of allowed AST types from an assignement AST node
* towards the root.
*/
private static final int[][] ALLOWED_ASSIGMENT_CONTEXT = {
{TokenTypes.EXPR, TokenTypes.SLIST},
{TokenTypes.VARIABLE_DEF},
{TokenTypes.EXPR, TokenTypes.ELIST, TokenTypes.FOR_INIT},
{TokenTypes.EXPR, TokenTypes.ELIST, TokenTypes.FOR_ITERATOR},
{TokenTypes.ANNOTATION_MEMBER_VALUE_PAIR},
};
/**
* list of allowed AST types from an assignement AST node
* towards the root.
*/
private static final int[][] CONTROL_CONTEXT = {
{TokenTypes.EXPR, TokenTypes.LITERAL_DO},
{TokenTypes.EXPR, TokenTypes.LITERAL_FOR},
{TokenTypes.EXPR, TokenTypes.LITERAL_WHILE},
{TokenTypes.EXPR, TokenTypes.LITERAL_IF},
{TokenTypes.EXPR, TokenTypes.LITERAL_ELSE},
};
/**
* list of allowed AST types from a comparison node (above an assignement)
* towards the root.
*/
private static final int[][] ALLOWED_ASSIGMENT_IN_COMPARISON_CONTEXT = {
{TokenTypes.EXPR, TokenTypes.LITERAL_WHILE, },
};
/**
* The token types that identify comparison operators.
*/
private static final int[] COMPARISON_TYPES = {
TokenTypes.EQUAL,
TokenTypes.GE,
TokenTypes.GT,
TokenTypes.LE,
TokenTypes.LT,
TokenTypes.NOT_EQUAL,
};
static {
Arrays.sort(COMPARISON_TYPES);
}
/** {@inheritDoc} */
public int[] getDefaultTokens()
{
return new int[] {
TokenTypes.ASSIGN, // '='
TokenTypes.DIV_ASSIGN, // "/="
TokenTypes.PLUS_ASSIGN, // "+="
TokenTypes.MINUS_ASSIGN, //"-="
TokenTypes.STAR_ASSIGN, // "*="
TokenTypes.MOD_ASSIGN, // "%="
TokenTypes.SR_ASSIGN, // ">>="
TokenTypes.BSR_ASSIGN, // ">>>="
TokenTypes.SL_ASSIGN, // "<<="
TokenTypes.BXOR_ASSIGN, // "^="
TokenTypes.BOR_ASSIGN, // "|="
TokenTypes.BAND_ASSIGN, // "&="
};
}
/** {@inheritDoc} */
public void visitToken(DetailAST aAST)
{
if (isInContext(aAST, ALLOWED_ASSIGMENT_CONTEXT)) {
return;
}
if (isInNoBraceControlStatement(aAST)) {
return;
}
if (isInWhileIdiom(aAST)) {
return;
}
log(aAST.getLineNo(), aAST.getColumnNo(), "assignment.inner.avoid");
}
/**
* Determines if aAST is in the body of a flow control statement without
* braces. An example of such a statement would be
* <p>
* <pre>
* if (y < 0)
* x = y;
* </pre>
* <p>
* This leads to the following AST structure:
* <p>
* <pre>
* LITERAL_IF
* LPAREN
* EXPR // test
* RPAREN
* EXPR // body
* SEMI
* </pre>
* <p>
* We need to ensure that aAST is in the body and not in the test.
*
* @param aAST an assignment operator AST
* @return whether aAST is in the body of a flow control statement
*/
private static boolean isInNoBraceControlStatement(DetailAST aAST)
{
if (!isInContext(aAST, CONTROL_CONTEXT)) {
return false;
}
final DetailAST expr = aAST.getParent();
final AST exprNext = expr.getNextSibling();
return (exprNext != null) && (exprNext.getType() == TokenTypes.SEMI);
}
/**
* Tests whether the given AST is used in the "assignment in while test"
* idiom.
* <p>
* <pre>
* while ((b = is.read()) != -1) {
* // work with b
* }
* <pre>
* @param aAST assignment AST
* @return whether the context of the assignemt AST indicates the idiom
*/
private boolean isInWhileIdiom(DetailAST aAST)
{
if (!isComparison(aAST.getParent())) {
return false;
}
return isInContext(
aAST.getParent(), ALLOWED_ASSIGMENT_IN_COMPARISON_CONTEXT);
}
/**
* Checks if an AST is a comparison operator.
* @param aAST the AST to check
* @return true iff aAST is a comparison operator.
*/
private static boolean isComparison(DetailAST aAST)
{
final int astType = aAST.getType();
return (Arrays.binarySearch(COMPARISON_TYPES, astType) >= 0);
}
/**
* Tests whether the provided AST is in
* one of the given contexts.
*
* @param aAST the AST from which to start walking towards root
* @param aContextSet the contexts to test against.
*
* @return whether the parents nodes of aAST match
* one of the allowed type paths
*/
private static boolean isInContext(DetailAST aAST, int[][] aContextSet)
{
for (int i = 0; i < aContextSet.length; i++) {
DetailAST current = aAST;
final int len = aContextSet[i].length;
for (int j = 0; j < len; j++) {
current = current.getParent();
final int expectedType = aContextSet[i][j];
if ((current == null) || (current.getType() != expectedType)) {
break;
}
if (j == len - 1) {
return true;
}
}
}
return false;
}
}
The table below shows all metrics for InnerAssignmentCheck.java.




