001////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code for adherence to a set of rules.
003// Copyright (C) 2001-2020 the original author or authors.
004//
005// This library is free software; you can redistribute it and/or
006// modify it under the terms of the GNU Lesser General Public
007// License as published by the Free Software Foundation; either
008// version 2.1 of the License, or (at your option) any later version.
009//
010// This library is distributed in the hope that it will be useful,
011// but WITHOUT ANY WARRANTY; without even the implied warranty of
012// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
013// Lesser General Public License for more details.
014//
015// You should have received a copy of the GNU Lesser General Public
016// License along with this library; if not, write to the Free Software
017// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
018////////////////////////////////////////////////////////////////////////////////
019
020package com.puppycrawl.tools.checkstyle.checks.javadoc;
021
022import java.util.ArrayDeque;
023import java.util.Arrays;
024import java.util.Collections;
025import java.util.Deque;
026import java.util.List;
027import java.util.Locale;
028import java.util.Set;
029import java.util.TreeSet;
030import java.util.regex.Pattern;
031import java.util.stream.Collectors;
032
033import com.puppycrawl.tools.checkstyle.JavadocDetailNodeParser;
034import com.puppycrawl.tools.checkstyle.StatelessCheck;
035import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
036import com.puppycrawl.tools.checkstyle.api.DetailAST;
037import com.puppycrawl.tools.checkstyle.api.FileContents;
038import com.puppycrawl.tools.checkstyle.api.Scope;
039import com.puppycrawl.tools.checkstyle.api.TextBlock;
040import com.puppycrawl.tools.checkstyle.api.TokenTypes;
041import com.puppycrawl.tools.checkstyle.utils.CheckUtil;
042import com.puppycrawl.tools.checkstyle.utils.CommonUtil;
043import com.puppycrawl.tools.checkstyle.utils.ScopeUtil;
044
045/**
046 * <p>
047 * Validates Javadoc comments to help ensure they are well formed.
048 * </p>
049 * <p>
050 * The following checks are performed:
051 * </p>
052 * <ul>
053 * <li>
054 * Ensures the first sentence ends with proper punctuation
055 * (That is a period, question mark, or exclamation mark, by default).
056 * Javadoc automatically places the first sentence in the method summary
057 * table and index. Without proper punctuation the Javadoc may be malformed.
058 * All items eligible for the {@code {@inheritDoc}} tag are exempt from this
059 * requirement.
060 * </li>
061 * <li>
062 * Check text for Javadoc statements that do not have any description.
063 * This includes both completely empty Javadoc, and Javadoc with only tags
064 * such as {@code @param} and {@code @return}.
065 * </li>
066 * <li>
067 * Check text for incomplete HTML tags. Verifies that HTML tags have
068 * corresponding end tags and issues an "Unclosed HTML tag found:" error if not.
069 * An "Extra HTML tag found:" error is issued if an end tag is found without
070 * a previous open tag.
071 * </li>
072 * <li>
073 * Check that a package Javadoc comment is well-formed (as described above) and
074 * NOT missing from any package-info.java files.
075 * </li>
076 * <li>
077 * Check for allowed HTML tags. The list of allowed HTML tags is
078 * "a", "abbr", "acronym", "address", "area", "b", "bdo", "big", "blockquote",
079 * "br", "caption", "cite", "code", "colgroup", "dd", "del", "dfn", "div", "dl",
080 * "dt", "em", "fieldset", "font", "h1", "h2", "h3", "h4", "h5", "h6", "hr",
081 * "i", "img", "ins", "kbd", "li", "ol", "p", "pre", "q", "samp", "small",
082 * "span", "strong", "sub", "sup", "table", "tbody", "td", "tfoot", "th",
083 * "thead", "tr", "tt", "u", "ul", "var".
084 * </li>
085 * </ul>
086 * <p>
087 * These checks were patterned after the checks made by the
088 * <a href="http://maven-doccheck.sourceforge.net/">DocCheck</a> doclet
089 * available from Sun. Note: Original Sun's DocCheck tool does not exist anymore.
090 * </p>
091 * <ul>
092 * <li>
093 * Property {@code scope} - Specify the visibility scope where Javadoc comments are checked.
094 * Type is {@code com.puppycrawl.tools.checkstyle.api.Scope}.
095 * Default value is {@code private}.
096 * </li>
097 * <li>
098 * Property {@code excludeScope} - Specify the visibility scope where
099 * Javadoc comments are not checked.
100 * Type is {@code com.puppycrawl.tools.checkstyle.api.Scope}.
101 * Default value is {@code null}.
102 * </li>
103 * <li>
104 * Property {@code checkFirstSentence} - Control whether to check the first
105 * sentence for proper end of sentence.
106 * Type is {@code boolean}.
107 * Default value is {@code true}.
108 * </li>
109 * <li>
110 * Property {@code endOfSentenceFormat} - Specify the format for matching
111 * the end of a sentence.
112 * Type is {@code java.util.regex.Pattern}.
113 * Default value is {@code "([.?!][ \t\n\r\f&lt;])|([.?!]$)"}.
114 * </li>
115 * <li>
116 * Property {@code checkEmptyJavadoc} - Control whether to check if the Javadoc
117 * is missing a describing text.
118 * Type is {@code boolean}.
119 * Default value is {@code false}.
120 * </li>
121 * <li>
122 * Property {@code checkHtml} - Control whether to check for incomplete HTML tags.
123 * Type is {@code boolean}.
124 * Default value is {@code true}.
125 * </li>
126 * <li>
127 * Property {@code tokens} - tokens to check
128 * Type is {@code java.lang.String[]}.
129 * Validation type is {@code tokenSet}.
130 * Default value is:
131 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#ANNOTATION_DEF">
132 * ANNOTATION_DEF</a>,
133 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#ANNOTATION_FIELD_DEF">
134 * ANNOTATION_FIELD_DEF</a>,
135 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#CLASS_DEF">
136 * CLASS_DEF</a>,
137 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#CTOR_DEF">
138 * CTOR_DEF</a>,
139 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#ENUM_CONSTANT_DEF">
140 * ENUM_CONSTANT_DEF</a>,
141 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#ENUM_DEF">
142 * ENUM_DEF</a>,
143 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#INTERFACE_DEF">
144 * INTERFACE_DEF</a>,
145 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#METHOD_DEF">
146 * METHOD_DEF</a>,
147 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#PACKAGE_DEF">
148 * PACKAGE_DEF</a>,
149 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#VARIABLE_DEF">
150 * VARIABLE_DEF</a>,
151 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#RECORD_DEF">
152 * RECORD_DEF</a>,
153 * <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#COMPACT_CTOR_DEF">
154 * COMPACT_CTOR_DEF</a>.
155 * </li>
156 * </ul>
157 * <p>
158 * To configure the default check:
159 * </p>
160 * <pre>
161 * &lt;module name="JavadocStyle"/&gt;
162 * </pre>
163 * <p>Example:</p>
164 * <pre>
165 * public class Test {
166 *     &#47;**
167 *      * Some description here. // OK
168 *      *&#47;
169 *     private void methodWithValidCommentStyle() {}
170 *
171 *     &#47;**
172 *      * Some description here // violation, the sentence must end with a proper punctuation
173 *      *&#47;
174 *     private void methodWithInvalidCommentStyle() {}
175 * }
176 * </pre>
177 * <p>
178 * To configure the check for {@code public} scope:
179 * </p>
180 * <pre>
181 * &lt;module name="JavadocStyle"&gt;
182 *   &lt;property name="scope" value="public"/&gt;
183 * &lt;/module&gt;
184 * </pre>
185 * <p>Example:</p>
186 * <pre>
187 * public class Test {
188 *     &#47;**
189 *      * Some description here // violation, the sentence must end with a proper punctuation
190 *      *&#47;
191 *     public void test1() {}
192 *
193 *     &#47;**
194 *      * Some description here // OK
195 *      *&#47;
196 *     private void test2() {}
197 * }
198 * </pre>
199 * <p>
200 * To configure the check for javadoc which is in {@code private}, but not in {@code package} scope:
201 * </p>
202 * <pre>
203 * &lt;module name="JavadocStyle"&gt;
204 *   &lt;property name="scope" value="private"/&gt;
205 *   &lt;property name="excludeScope" value="package"/&gt;
206 * &lt;/module&gt;
207 * </pre>
208 * <p>Example:</p>
209 * <pre>
210 * public class Test {
211 *     &#47;**
212 *      * Some description here // violation, the sentence must end with a proper punctuation
213 *      *&#47;
214 *     private void test1() {}
215 *
216 *     &#47;**
217 *      * Some description here // OK
218 *      *&#47;
219 *     void test2() {}
220 * }
221 * </pre>
222 * <p>
223 * To configure the check to turn off first sentence checking:
224 * </p>
225 * <pre>
226 * &lt;module name="JavadocStyle"&gt;
227 *   &lt;property name="checkFirstSentence" value="false"/&gt;
228 * &lt;/module&gt;
229 * </pre>
230 * <p>Example:</p>
231 * <pre>
232 * public class Test {
233 *     &#47;**
234 *      * Some description here // OK
235 *      * Second line of description // violation, the sentence must end with a proper punctuation
236 *      *&#47;
237 *     private void test1() {}
238 * }
239 * </pre>
240 * <p>
241 * To configure the check to turn off validation of incomplete html tags:
242 * </p>
243 * <pre>
244 * &lt;module name="JavadocStyle"&gt;
245 * &lt;property name="checkHtml" value="false"/&gt;
246 * &lt;/module&gt;
247 * </pre>
248 * <p>Example:</p>
249 * <pre>
250 * public class Test {
251 *     &#47;**
252 *      * Some description here // violation, the sentence must end with a proper punctuation
253 *      * &lt;p // OK
254 *      *&#47;
255 *     private void test1() {}
256 * }
257 * </pre>
258 * <p>
259 * To configure the check for only class definitions:
260 * </p>
261 * <pre>
262 * &lt;module name="JavadocStyle"&gt;
263 * &lt;property name="tokens" value="CLASS_DEF"/&gt;
264 * &lt;/module&gt;
265 * </pre>
266 * <p>Example:</p>
267 * <pre>
268 * &#47;**
269 *  * Some description here // violation, the sentence must end with a proper punctuation
270 *  *&#47;
271 * public class Test {
272 *     &#47;**
273 *      * Some description here // OK
274 *      *&#47;
275 *     private void test1() {}
276 * }
277 * </pre>
278 * <p>
279 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
280 * </p>
281 * <p>
282 * Violation Message Keys:
283 * </p>
284 * <ul>
285 * <li>
286 * {@code javadoc.empty}
287 * </li>
288 * <li>
289 * {@code javadoc.extraHtml}
290 * </li>
291 * <li>
292 * {@code javadoc.incompleteTag}
293 * </li>
294 * <li>
295 * {@code javadoc.missing}
296 * </li>
297 * <li>
298 * {@code javadoc.noPeriod}
299 * </li>
300 * <li>
301 * {@code javadoc.unclosedHtml}
302 * </li>
303 * </ul>
304 *
305 * @since 3.2
306 */
307@StatelessCheck
308public class JavadocStyleCheck
309    extends AbstractCheck {
310
311    /** Message property key for the Missing Javadoc message. */
312    public static final String MSG_JAVADOC_MISSING = "javadoc.missing";
313
314    /** Message property key for the Empty Javadoc message. */
315    public static final String MSG_EMPTY = "javadoc.empty";
316
317    /** Message property key for the No Javadoc end of Sentence Period message. */
318    public static final String MSG_NO_PERIOD = "javadoc.noPeriod";
319
320    /** Message property key for the Incomplete Tag message. */
321    public static final String MSG_INCOMPLETE_TAG = "javadoc.incompleteTag";
322
323    /** Message property key for the Unclosed HTML message. */
324    public static final String MSG_UNCLOSED_HTML = JavadocDetailNodeParser.MSG_UNCLOSED_HTML_TAG;
325
326    /** Message property key for the Extra HTML message. */
327    public static final String MSG_EXTRA_HTML = "javadoc.extraHtml";
328
329    /** HTML tags that do not require a close tag. */
330    private static final Set<String> SINGLE_TAGS = Collections.unmodifiableSortedSet(
331        Arrays.stream(new String[] {"br", "li", "dt", "dd", "hr", "img", "p", "td", "tr", "th", })
332            .collect(Collectors.toCollection(TreeSet::new)));
333
334    /**
335     * HTML tags that are allowed in java docs.
336     * From https://www.w3schools.com/tags/default.asp
337     * The forms and structure tags are not allowed
338     */
339    private static final Set<String> ALLOWED_TAGS = Collections.unmodifiableSortedSet(
340        Arrays.stream(new String[] {
341            "a", "abbr", "acronym", "address", "area", "b", "bdo", "big",
342            "blockquote", "br", "caption", "cite", "code", "colgroup", "dd",
343            "del", "dfn", "div", "dl", "dt", "em", "fieldset", "font", "h1",
344            "h2", "h3", "h4", "h5", "h6", "hr", "i", "img", "ins", "kbd",
345            "li", "ol", "p", "pre", "q", "samp", "small", "span", "strong",
346            "sub", "sup", "table", "tbody", "td", "tfoot", "th", "thead",
347            "tr", "tt", "u", "ul", "var", })
348        .collect(Collectors.toCollection(TreeSet::new)));
349
350    /** Specify the visibility scope where Javadoc comments are checked. */
351    private Scope scope = Scope.PRIVATE;
352
353    /** Specify the visibility scope where Javadoc comments are not checked. */
354    private Scope excludeScope;
355
356    /** Specify the format for matching the end of a sentence. */
357    private Pattern endOfSentenceFormat = Pattern.compile("([.?!][ \t\n\r\f<])|([.?!]$)");
358
359    /**
360     * Control whether to check the first sentence for proper end of sentence.
361     */
362    private boolean checkFirstSentence = true;
363
364    /**
365     * Control whether to check for incomplete HTML tags.
366     */
367    private boolean checkHtml = true;
368
369    /**
370     * Control whether to check if the Javadoc is missing a describing text.
371     */
372    private boolean checkEmptyJavadoc;
373
374    @Override
375    public int[] getDefaultTokens() {
376        return getAcceptableTokens();
377    }
378
379    @Override
380    public int[] getAcceptableTokens() {
381        return new int[] {
382            TokenTypes.ANNOTATION_DEF,
383            TokenTypes.ANNOTATION_FIELD_DEF,
384            TokenTypes.CLASS_DEF,
385            TokenTypes.CTOR_DEF,
386            TokenTypes.ENUM_CONSTANT_DEF,
387            TokenTypes.ENUM_DEF,
388            TokenTypes.INTERFACE_DEF,
389            TokenTypes.METHOD_DEF,
390            TokenTypes.PACKAGE_DEF,
391            TokenTypes.VARIABLE_DEF,
392            TokenTypes.RECORD_DEF,
393            TokenTypes.COMPACT_CTOR_DEF,
394        };
395    }
396
397    @Override
398    public int[] getRequiredTokens() {
399        return CommonUtil.EMPTY_INT_ARRAY;
400    }
401
402    @Override
403    public void visitToken(DetailAST ast) {
404        if (shouldCheck(ast)) {
405            final FileContents contents = getFileContents();
406            // Need to start searching for the comment before the annotations
407            // that may exist. Even if annotations are not defined on the
408            // package, the ANNOTATIONS AST is defined.
409            final TextBlock textBlock =
410                contents.getJavadocBefore(ast.getFirstChild().getLineNo());
411
412            checkComment(ast, textBlock);
413        }
414    }
415
416    /**
417     * Whether we should check this node.
418     *
419     * @param ast a given node.
420     * @return whether we should check a given node.
421     */
422    private boolean shouldCheck(final DetailAST ast) {
423        boolean check = false;
424
425        if (ast.getType() == TokenTypes.PACKAGE_DEF) {
426            check = getFileContents().inPackageInfo();
427        }
428        else if (!ScopeUtil.isInCodeBlock(ast)) {
429            final Scope customScope;
430
431            if (ScopeUtil.isInInterfaceOrAnnotationBlock(ast)
432                    || ast.getType() == TokenTypes.ENUM_CONSTANT_DEF) {
433                customScope = Scope.PUBLIC;
434            }
435            else {
436                customScope = ScopeUtil.getScopeFromMods(ast.findFirstToken(TokenTypes.MODIFIERS));
437            }
438            final Scope surroundingScope = ScopeUtil.getSurroundingScope(ast);
439
440            check = customScope.isIn(scope)
441                    && (surroundingScope == null || surroundingScope.isIn(scope))
442                    && (excludeScope == null
443                        || !customScope.isIn(excludeScope)
444                        || surroundingScope != null
445                            && !surroundingScope.isIn(excludeScope));
446        }
447        return check;
448    }
449
450    /**
451     * Performs the various checks against the Javadoc comment.
452     *
453     * @param ast the AST of the element being documented
454     * @param comment the source lines that make up the Javadoc comment.
455     *
456     * @see #checkFirstSentenceEnding(DetailAST, TextBlock)
457     * @see #checkHtmlTags(DetailAST, TextBlock)
458     */
459    private void checkComment(final DetailAST ast, final TextBlock comment) {
460        if (comment == null) {
461            // checking for missing docs in JavadocStyleCheck is not consistent
462            // with the rest of CheckStyle...  Even though, I didn't think it
463            // made sense to make another check just to ensure that the
464            // package-info.java file actually contains package Javadocs.
465            if (getFileContents().inPackageInfo()) {
466                log(ast, MSG_JAVADOC_MISSING);
467            }
468        }
469        else {
470            if (checkFirstSentence) {
471                checkFirstSentenceEnding(ast, comment);
472            }
473
474            if (checkHtml) {
475                checkHtmlTags(ast, comment);
476            }
477
478            if (checkEmptyJavadoc) {
479                checkJavadocIsNotEmpty(comment);
480            }
481        }
482    }
483
484    /**
485     * Checks that the first sentence ends with proper punctuation.  This method
486     * uses a regular expression that checks for the presence of a period,
487     * question mark, or exclamation mark followed either by whitespace, an
488     * HTML element, or the end of string. This method ignores {_AT_inheritDoc}
489     * comments for TokenTypes that are valid for {_AT_inheritDoc}.
490     *
491     * @param ast the current node
492     * @param comment the source lines that make up the Javadoc comment.
493     */
494    private void checkFirstSentenceEnding(final DetailAST ast, TextBlock comment) {
495        final String commentText = getCommentText(comment.getText());
496
497        if (!commentText.isEmpty()
498            && !endOfSentenceFormat.matcher(commentText).find()
499            && !(commentText.startsWith("{@inheritDoc}")
500            && JavadocTagInfo.INHERIT_DOC.isValidOn(ast))) {
501            log(comment.getStartLineNo(), MSG_NO_PERIOD);
502        }
503    }
504
505    /**
506     * Checks that the Javadoc is not empty.
507     *
508     * @param comment the source lines that make up the Javadoc comment.
509     */
510    private void checkJavadocIsNotEmpty(TextBlock comment) {
511        final String commentText = getCommentText(comment.getText());
512
513        if (commentText.isEmpty()) {
514            log(comment.getStartLineNo(), MSG_EMPTY);
515        }
516    }
517
518    /**
519     * Returns the comment text from the Javadoc.
520     *
521     * @param comments the lines of Javadoc.
522     * @return a comment text String.
523     */
524    private static String getCommentText(String... comments) {
525        final StringBuilder builder = new StringBuilder(1024);
526        for (final String line : comments) {
527            final int textStart = findTextStart(line);
528
529            if (textStart != -1) {
530                if (line.charAt(textStart) == '@') {
531                    // we have found the tag section
532                    break;
533                }
534                builder.append(line.substring(textStart));
535                trimTail(builder);
536                builder.append('\n');
537            }
538        }
539
540        return builder.toString().trim();
541    }
542
543    /**
544     * Finds the index of the first non-whitespace character ignoring the
545     * Javadoc comment start and end strings (&#47** and *&#47) as well as any
546     * leading asterisk.
547     *
548     * @param line the Javadoc comment line of text to scan.
549     * @return the int index relative to 0 for the start of text
550     *         or -1 if not found.
551     */
552    private static int findTextStart(String line) {
553        int textStart = -1;
554        int index = 0;
555        while (index < line.length()) {
556            if (!Character.isWhitespace(line.charAt(index))) {
557                if (line.regionMatches(index, "/**", 0, "/**".length())) {
558                    index += 2;
559                }
560                else if (line.regionMatches(index, "*/", 0, 2)) {
561                    index++;
562                }
563                else if (line.charAt(index) != '*') {
564                    textStart = index;
565                    break;
566                }
567            }
568            index++;
569        }
570        return textStart;
571    }
572
573    /**
574     * Trims any trailing whitespace or the end of Javadoc comment string.
575     *
576     * @param builder the StringBuilder to trim.
577     */
578    private static void trimTail(StringBuilder builder) {
579        int index = builder.length() - 1;
580        while (true) {
581            if (Character.isWhitespace(builder.charAt(index))) {
582                builder.deleteCharAt(index);
583            }
584            else if (index > 0 && builder.charAt(index) == '/'
585                    && builder.charAt(index - 1) == '*') {
586                builder.deleteCharAt(index);
587                builder.deleteCharAt(index - 1);
588                index--;
589                while (builder.charAt(index - 1) == '*') {
590                    builder.deleteCharAt(index - 1);
591                    index--;
592                }
593            }
594            else {
595                break;
596            }
597            index--;
598        }
599    }
600
601    /**
602     * Checks the comment for HTML tags that do not have a corresponding close
603     * tag or a close tag that has no previous open tag.  This code was
604     * primarily copied from the DocCheck checkHtml method.
605     *
606     * @param ast the node with the Javadoc
607     * @param comment the {@code TextBlock} which represents
608     *                 the Javadoc comment.
609     * @noinspection MethodWithMultipleReturnPoints
610     */
611    // -@cs[ReturnCount] Too complex to break apart.
612    private void checkHtmlTags(final DetailAST ast, final TextBlock comment) {
613        final int lineNo = comment.getStartLineNo();
614        final Deque<HtmlTag> htmlStack = new ArrayDeque<>();
615        final String[] text = comment.getText();
616
617        final TagParser parser = new TagParser(text, lineNo);
618
619        while (parser.hasNextTag()) {
620            final HtmlTag tag = parser.nextTag();
621
622            if (tag.isIncompleteTag()) {
623                log(tag.getLineNo(), MSG_INCOMPLETE_TAG,
624                    text[tag.getLineNo() - lineNo]);
625                return;
626            }
627            if (tag.isClosedTag()) {
628                // do nothing
629                continue;
630            }
631            if (tag.isCloseTag()) {
632                // We have found a close tag.
633                if (isExtraHtml(tag.getId(), htmlStack)) {
634                    // No corresponding open tag was found on the stack.
635                    log(tag.getLineNo(),
636                        tag.getPosition(),
637                        MSG_EXTRA_HTML,
638                        tag.getText());
639                }
640                else {
641                    // See if there are any unclosed tags that were opened
642                    // after this one.
643                    checkUnclosedTags(htmlStack, tag.getId());
644                }
645            }
646            else {
647                // We only push html tags that are allowed
648                if (isAllowedTag(tag)) {
649                    htmlStack.push(tag);
650                }
651            }
652        }
653
654        // Identify any tags left on the stack.
655        // Skip multiples, like <b>...<b>
656        String lastFound = "";
657        final List<String> typeParameters = CheckUtil.getTypeParameterNames(ast);
658        for (final HtmlTag htmlTag : htmlStack) {
659            if (!isSingleTag(htmlTag)
660                && !htmlTag.getId().equals(lastFound)
661                && !typeParameters.contains(htmlTag.getId())) {
662                log(htmlTag.getLineNo(), htmlTag.getPosition(),
663                        MSG_UNCLOSED_HTML, htmlTag.getText());
664                lastFound = htmlTag.getId();
665            }
666        }
667    }
668
669    /**
670     * Checks to see if there are any unclosed tags on the stack.  The token
671     * represents a html tag that has been closed and has a corresponding open
672     * tag on the stack.  Any tags, except single tags, that were opened
673     * (pushed on the stack) after the token are missing a close.
674     *
675     * @param htmlStack the stack of opened HTML tags.
676     * @param token the current HTML tag name that has been closed.
677     */
678    private void checkUnclosedTags(Deque<HtmlTag> htmlStack, String token) {
679        final Deque<HtmlTag> unclosedTags = new ArrayDeque<>();
680        HtmlTag lastOpenTag = htmlStack.pop();
681        while (!token.equalsIgnoreCase(lastOpenTag.getId())) {
682            // Find unclosed elements. Put them on a stack so the
683            // output order won't be back-to-front.
684            if (isSingleTag(lastOpenTag)) {
685                lastOpenTag = htmlStack.pop();
686            }
687            else {
688                unclosedTags.push(lastOpenTag);
689                lastOpenTag = htmlStack.pop();
690            }
691        }
692
693        // Output the unterminated tags, if any
694        // Skip multiples, like <b>..<b>
695        String lastFound = "";
696        for (final HtmlTag htag : unclosedTags) {
697            lastOpenTag = htag;
698            if (lastOpenTag.getId().equals(lastFound)) {
699                continue;
700            }
701            lastFound = lastOpenTag.getId();
702            log(lastOpenTag.getLineNo(),
703                lastOpenTag.getPosition(),
704                MSG_UNCLOSED_HTML,
705                lastOpenTag.getText());
706        }
707    }
708
709    /**
710     * Determines if the HtmlTag is one which does not require a close tag.
711     *
712     * @param tag the HtmlTag to check.
713     * @return {@code true} if the HtmlTag is a single tag.
714     */
715    private static boolean isSingleTag(HtmlTag tag) {
716        // If its a singleton tag (<p>, <br>, etc.), ignore it
717        // Can't simply not put them on the stack, since singletons
718        // like <dt> and <dd> (unhappily) may either be terminated
719        // or not terminated. Both options are legal.
720        return SINGLE_TAGS.contains(tag.getId().toLowerCase(Locale.ENGLISH));
721    }
722
723    /**
724     * Determines if the HtmlTag is one which is allowed in a javadoc.
725     *
726     * @param tag the HtmlTag to check.
727     * @return {@code true} if the HtmlTag is an allowed html tag.
728     */
729    private static boolean isAllowedTag(HtmlTag tag) {
730        return ALLOWED_TAGS.contains(tag.getId().toLowerCase(Locale.ENGLISH));
731    }
732
733    /**
734     * Determines if the given token is an extra HTML tag. This indicates that
735     * a close tag was found that does not have a corresponding open tag.
736     *
737     * @param token an HTML tag id for which a close was found.
738     * @param htmlStack a Stack of previous open HTML tags.
739     * @return {@code false} if a previous open tag was found
740     *         for the token.
741     */
742    private static boolean isExtraHtml(String token, Deque<HtmlTag> htmlStack) {
743        boolean isExtra = true;
744        for (final HtmlTag tag : htmlStack) {
745            // Loop, looking for tags that are closed.
746            // The loop is needed in case there are unclosed
747            // tags on the stack. In that case, the stack would
748            // not be empty, but this tag would still be extra.
749            if (token.equalsIgnoreCase(tag.getId())) {
750                isExtra = false;
751                break;
752            }
753        }
754
755        return isExtra;
756    }
757
758    /**
759     * Setter to specify the visibility scope where Javadoc comments are checked.
760     *
761     * @param scope a scope.
762     */
763    public void setScope(Scope scope) {
764        this.scope = scope;
765    }
766
767    /**
768     * Setter to specify the visibility scope where Javadoc comments are not checked.
769     *
770     * @param excludeScope a scope.
771     */
772    public void setExcludeScope(Scope excludeScope) {
773        this.excludeScope = excludeScope;
774    }
775
776    /**
777     * Setter to specify the format for matching the end of a sentence.
778     *
779     * @param pattern a pattern.
780     */
781    public void setEndOfSentenceFormat(Pattern pattern) {
782        endOfSentenceFormat = pattern;
783    }
784
785    /**
786     * Setter to control whether to check the first sentence for proper end of sentence.
787     *
788     * @param flag {@code true} if the first sentence is to be checked
789     */
790    public void setCheckFirstSentence(boolean flag) {
791        checkFirstSentence = flag;
792    }
793
794    /**
795     * Setter to control whether to check for incomplete HTML tags.
796     *
797     * @param flag {@code true} if HTML checking is to be performed.
798     */
799    public void setCheckHtml(boolean flag) {
800        checkHtml = flag;
801    }
802
803    /**
804     * Setter to control whether to check if the Javadoc is missing a describing text.
805     *
806     * @param flag {@code true} if empty Javadoc checking should be done.
807     */
808    public void setCheckEmptyJavadoc(boolean flag) {
809        checkEmptyJavadoc = flag;
810    }
811
812}