////////////////////////////////////////////////////////////////////////////////
// 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;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.regex.Pattern;
import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
import com.puppycrawl.tools.checkstyle.api.DetailAST;
import com.puppycrawl.tools.checkstyle.api.TextBlock;
import com.puppycrawl.tools.checkstyle.utils.CommonUtils;
/**
* <p>
* The check to ensure that comments are the only thing on a line.
* For the case of // comments that means that the only thing that should
* precede it is whitespace.
* It doesn't check comments if they do not end line, i.e. it accept
* the following:
* {@code Thread.sleep( 10 <some comment here> );}
* Format property is intended to deal with the "} // while" example.
* </p>
*
* <p>Rationale: Steve McConnel in "Code Complete" suggests that endline
* comments are a bad practice. An end line comment would
* be one that is on the same line as actual code. For example:
* <pre>
* a = b + c; // Some insightful comment
* d = e / f; // Another comment for this line
* </pre>
* Quoting "Code Complete" for the justification:
* <ul>
* <li>
* "The comments have to be aligned so that they do not
* interfere with the visual structure of the code. If you don't
* align them neatly, they'll make your listing look like it's been
* through a washing machine."
* </li>
* <li>
* "Endline comments tend to be hard to format...It takes time
* to align them. Such time is not spent learning more about
* the code; it's dedicated solely to the tedious task of
* pressing the spacebar or tab key."
* </li>
* <li>
* "Endline comments are also hard to maintain. If the code on
* any line containing an endline comment grows, it bumps the
* comment farther out, and all the other endline comments will
* have to bumped out to match. Styles that are hard to
* maintain aren't maintained...."
* </li>
* <li>
* "Endline comments also tend to be cryptic. The right side of
* the line doesn't offer much room and the desire to keep the
* comment on one line means the comment must be short.
* Work then goes into making the line as short as possible
* instead of as clear as possible. The comment usually ends
* up as cryptic as possible...."
* </li>
* <li>
* "A systemic problem with endline comments is that it's hard
* to write a meaningful comment for one line of code. Most
* endline comments just repeat the line of code, which hurts
* more than it helps."
* </li>
* </ul>
* His comments on being hard to maintain when the size of
* the line changes are even more important in the age of
* automated refactorings.
*
* <p>To configure the check so it enforces only comment on a line:
* <pre>
* <module name="TrailingComment">
* <property name="format" value="^\\s*$"/>
* </module>
* </pre>
*
* @author o_sukhodolsky
*/
public class TrailingCommentCheck extends AbstractCheck {
/**
* A key is pointing to the warning message text in "messages.properties"
* file.
*/
public static final String MSG_KEY = "trailing.comments";
/** Pattern for legal trailing comment. */
private Pattern legalComment;
/** The regexp to match against. */
private Pattern format = Pattern.compile("^[\\s});]*$");
/**
* Sets patter for legal trailing comments.
* @param legalComment pattern to set.
*/
public void setLegalComment(final Pattern legalComment) {
this.legalComment = legalComment;
}
/**
* Set the format for the specified regular expression.
* @param pattern a pattern
*/
public final void setFormat(Pattern pattern) {
format = pattern;
}
@Override
public int[] getDefaultTokens() {
return CommonUtils.EMPTY_INT_ARRAY;
}
@Override
public int[] getAcceptableTokens() {
return CommonUtils.EMPTY_INT_ARRAY;
}
@Override
public int[] getRequiredTokens() {
return CommonUtils.EMPTY_INT_ARRAY;
}
@Override
public void visitToken(DetailAST ast) {
throw new IllegalStateException("visitToken() shouldn't be called.");
}
@Override
public void beginTree(DetailAST rootAST) {
final Map<Integer, TextBlock> cppComments = getFileContents()
.getSingleLineComments();
final Map<Integer, List<TextBlock>> cComments = getFileContents()
.getBlockComments();
final Set<Integer> lines = new HashSet<>();
lines.addAll(cppComments.keySet());
lines.addAll(cComments.keySet());
for (Integer lineNo : lines) {
final String line = getLines()[lineNo - 1];
final String lineBefore;
final TextBlock comment;
if (cppComments.containsKey(lineNo)) {
comment = cppComments.get(lineNo);
lineBefore = line.substring(0, comment.getStartColNo());
}
else {
final List<TextBlock> commentList = cComments.get(lineNo);
comment = commentList.get(commentList.size() - 1);
lineBefore = line.substring(0, comment.getStartColNo());
// do not check comment which doesn't end line
if (comment.getText().length == 1
&& !CommonUtils.isBlank(line
.substring(comment.getEndColNo() + 1))) {
continue;
}
}
if (!format.matcher(lineBefore).find()
&& !isLegalComment(comment)) {
log(lineNo, MSG_KEY);
}
}
}
/**
* Checks if given comment is legal (single-line and matches to the
* pattern).
* @param comment comment to check.
* @return true if the comment if legal.
*/
private boolean isLegalComment(final TextBlock comment) {
final boolean legal;
// multi-line comment can not be legal
if (legalComment == null || comment.getStartLineNo() != comment.getEndLineNo()) {
legal = false;
}
else {
String commentText = comment.getText()[0];
// remove chars which start comment
commentText = commentText.substring(2);
// if this is a C-style comment we need to remove its end
if (commentText.endsWith("*/")) {
commentText = commentText.substring(0, commentText.length() - 2);
}
commentText = commentText.trim();
legal = legalComment.matcher(commentText).find();
}
return legal;
}
}