////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code for adherence to a set of rules.
// Copyright (C) 2001-2017 the original author or authors.
//
// 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.AbstractCheck;
import com.puppycrawl.tools.checkstyle.api.DetailAST;
import com.puppycrawl.tools.checkstyle.api.TokenTypes;
/**
* <p>
* Checks for assignments in subexpressions, such as in
* {@code String s = Integer.toString(i = 2);}.
* </p>
* <p>
* Rationale: With the exception of {@code for} iterators, all assignments
* should occur in their own top-level 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 AbstractCheck {
/**
* A key is pointing to the warning message text in "messages.properties"
* file.
*/
public static final String MSG_KEY = "assignment.inner.avoid";
/**
* List of allowed AST types from an assignment AST node
* towards the root.
*/
private static final int[][] ALLOWED_ASSIGNMENT_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}, {
TokenTypes.RESOURCE,
TokenTypes.RESOURCES,
TokenTypes.RESOURCE_SPECIFICATION,
},
{TokenTypes.EXPR, TokenTypes.LAMBDA},
};
/**
* List of allowed AST types from an assignment 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 assignment)
* towards the root.
*/
private static final int[][] ALLOWED_ASSIGNMENT_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);
}
@Override
public int[] getDefaultTokens() {
return getAcceptableTokens();
}
@Override
public int[] getAcceptableTokens() {
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, // "&="
};
}
@Override
public int[] getRequiredTokens() {
return getAcceptableTokens();
}
@Override
public void visitToken(DetailAST ast) {
if (!isInContext(ast, ALLOWED_ASSIGNMENT_CONTEXT)
&& !isInNoBraceControlStatement(ast)
&& !isInWhileIdiom(ast)) {
log(ast.getLineNo(), ast.getColumnNo(), MSG_KEY);
}
}
/**
* Determines if ast 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>
* <p>
* This leads to the following AST structure:
* </p>
* <p>
* <pre>
* LITERAL_IF
* LPAREN
* EXPR // test
* RPAREN
* EXPR // body
* SEMI
* </pre>
* </p>
* <p>
* We need to ensure that ast is in the body and not in the test.
* </p>
*
* @param ast an assignment operator AST
* @return whether ast is in the body of a flow control statement
*/
private static boolean isInNoBraceControlStatement(DetailAST ast) {
if (!isInContext(ast, CONTROL_CONTEXT)) {
return false;
}
final DetailAST expr = ast.getParent();
final AST exprNext = expr.getNextSibling();
return exprNext.getType() == TokenTypes.SEMI;
}
/**
* Tests whether the given AST is used in the "assignment in while" idiom.
* <pre>
* String line;
* while ((line = bufferedReader.readLine()) != null) {
* // process the line
* }
* </pre>
* Assignment inside a condition is not a problem here, as the assignment is surrounded by an
* extra pair of parentheses. The comparison is {@code != null} and there is no chance that
* intention was to write {@code line == reader.readLine()}.
*
* @param ast assignment AST
* @return whether the context of the assignment AST indicates the idiom
*/
private static boolean isInWhileIdiom(DetailAST ast) {
if (!isComparison(ast.getParent())) {
return false;
}
return isInContext(
ast.getParent(), ALLOWED_ASSIGNMENT_IN_COMPARISON_CONTEXT);
}
/**
* Checks if an AST is a comparison operator.
* @param ast the AST to check
* @return true iff ast is a comparison operator.
*/
private static boolean isComparison(DetailAST ast) {
final int astType = ast.getType();
return Arrays.binarySearch(COMPARISON_TYPES, astType) >= 0;
}
/**
* Tests whether the provided AST is in
* one of the given contexts.
*
* @param ast the AST from which to start walking towards root
* @param contextSet the contexts to test against.
*
* @return whether the parents nodes of ast match one of the allowed type paths.
*/
private static boolean isInContext(DetailAST ast, int[]... contextSet) {
boolean found = false;
for (int[] element : contextSet) {
DetailAST current = ast;
for (int anElement : element) {
current = current.getParent();
if (current.getType() == anElement) {
found = true;
}
else {
found = false;
break;
}
}
if (found) {
break;
}
}
return found;
}
}