Issue #14689: Prevent false positives when first sentence of Javadoc is on its own line

src/it/java/com/google/checkstyle/test/chapter7javadoc/rule72thesummaryfragment/SummaryJavadocTest.java

@@ -54,6 +54,7 @@ public void testIncorrect() throws Exception {
             "summary.javaDoc.missing");
 
         final String[] expected = {
+            "9: " + msgFirstSentence,
             "14: " + msgMissingDoc,
             "32: " + msgMissingDoc,
             "37: " + msgFirstSentence,

src/it/resources/com/google/checkstyle/test/chapter7javadoc/rule72thesummaryfragment/InputIncorrectSummaryJavaDocCheck.java

@@ -6,7 +6,7 @@
  */
 class InputIncorrectSummaryJavaDocCheck {
 
-    /**
+/*warn*//**
      * As of JDK 1.1, replaced by {@link #setBounds(int,int,int,int)}
      */
     void foo3() {}

src/main/java/com/puppycrawl/tools/checkstyle/checks/javadoc/SummaryJavadocCheck.java

@@ -19,10 +19,15 @@
 
 package com.puppycrawl.tools.checkstyle.checks.javadoc;
 
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.BitSet;
+import java.util.List;
 import java.util.Optional;
 import java.util.regex.Pattern;
+import java.util.stream.Stream;
+
+import javax.annotation.Nullable;
 
 import com.puppycrawl.tools.checkstyle.StatelessCheck;
 import com.puppycrawl.tools.checkstyle.api.DetailNode;
@@ -48,7 +53,10 @@
  * Default value is {@code "^$"}.
  * </li>
  * <li>
- * Property {@code period} - Specify the period symbol at the end of first javadoc sentence.
+ * Property {@code period} - Specify the period symbol. Used to check the first sentence ends with a
+ * period. Periods that are not followed by a whitespace character are ignored (eg. the period in
+ * v1.0). Because some periods include whitespace built into the character, if this is set to a
+ * non-default value any period will end the sentence, whether it is followed by whitespace or not.
  * Type is {@code java.lang.String}.
  * Default value is {@code "."}.
  * </li>
@@ -154,7 +162,10 @@ public class SummaryJavadocCheck extends AbstractJavadocCheck {
     private Pattern forbiddenSummaryFragments = CommonUtil.createPattern("^$");
 
     /**
-     * Specify the period symbol at the end of first javadoc sentence.
+     * Specify the period symbol. Used to check the first sentence ends with a period. Periods that
+     * are not followed by a whitespace character are ignored (eg. the period in v1.0). Because some
+     * periods include whitespace built into the character, if this is set to a non-default value
+     * any period will end the sentence, whether it is followed by whitespace or not.
      */
     private String period = DEFAULT_PERIOD;
 
@@ -169,7 +180,11 @@ public void setForbiddenSummaryFragments(Pattern pattern) {
     }
 
     /**
-     * Setter to specify the period symbol at the end of first javadoc sentence.
+     * Setter to specify the period symbol. Used to check the first sentence ends with a period.
+     * Periods that are not followed by a whitespace character are ignored (eg. the period in v1.0).
+     * Because some periods include whitespace built into the character, if this is set to a
+     * non-default value any period will end the sentence, whether it is followed by whitespace or
+     * not.
      *
      * @param period period's value.
      * @since 6.2
@@ -218,14 +233,17 @@ private void validateUntaggedSummary(DetailNode ast) {
             log(ast.getLineNumber(), MSG_SUMMARY_JAVADOC_MISSING);
         }
         else if (!period.isEmpty()) {
-            final String firstSentence = getFirstSentence(ast);
-            final int endOfSentence = firstSentence.lastIndexOf(period);
-            if (!summaryDoc.contains(period)) {
-                log(ast.getLineNumber(), MSG_SUMMARY_FIRST_SENTENCE);
+            if (summaryDoc.contains(period)) {
+                final String firstSentence = getFirstSentenceOrNull(ast, period);
+                if (firstSentence == null) {
+                    log(ast.getLineNumber(), MSG_SUMMARY_FIRST_SENTENCE);
+                }
+                else if (containsForbiddenFragment(firstSentence)) {
+                    log(ast.getLineNumber(), MSG_SUMMARY_JAVADOC);
+                }
             }
-            if (endOfSentence != -1
-                    && containsForbiddenFragment(firstSentence.substring(0, endOfSentence))) {
-                log(ast.getLineNumber(), MSG_SUMMARY_JAVADOC);
+            else {
+                log(ast.getLineNumber(), MSG_SUMMARY_FIRST_SENTENCE);
             }
         }
     }
@@ -576,31 +594,76 @@ private static String getStringInsideTag(String result, DetailNode detailNode) {
     }
 
     /**
-     * Finds and returns first sentence.
+     * Finds and returns the first sentence.
      *
-     * @param ast Javadoc root node.
-     * @return first sentence.
+     * @param ast The Javadoc root node.
+     * @param period The configured period symbol.
+     * @return The first sentence up to and excluding the period, or null if no ending was found.
      */
-    private static String getFirstSentence(DetailNode ast) {
-        final StringBuilder result = new StringBuilder(256);
-        final String periodSuffix = DEFAULT_PERIOD + ' ';
-        for (DetailNode child : ast.getChildren()) {
-            final String text;
-            if (child.getChildren().length == 0) {
-                text = child.getText();
+    @Nullable
+    private static String getFirstSentenceOrNull(DetailNode ast, String period) {
+        final List<String> sentenceParts = new ArrayList<>();
+        String sentence = null;
+        for (String text : (Iterable<String>) streamTextParts(ast)::iterator) {
+            final String sentenceEnding = findSentenceEndingOrNull(text, period);
+            if (sentenceEnding != null) {
+                sentenceParts.add(sentenceEnding);
+                sentence = String.join("", sentenceParts);
+                break;
             }
             else {
-                text = getFirstSentence(child);
+                sentenceParts.add(text);
             }
+        }
+        return sentence;
+    }
 
-            if (text.contains(periodSuffix)) {
-                result.append(text, 0, text.indexOf(periodSuffix) + 1);
+    /**
+     * Streams through all the text under the given node.
+     *
+     * @param node The Javadoc node to examine.
+     * @return All the text in all nodes that have no child nodes.
+     */
+    private static Stream<String> streamTextParts(DetailNode node) {
+        final Stream<String> stream;
+        if (node.getChildren().length == 0) {
+            stream = Stream.of(node.getText());
+        }
+        else {
+            stream = Stream.of(node.getChildren())
+                .flatMap(SummaryJavadocCheck::streamTextParts);
+        }
+        return stream;
+    }
+
+    /**
+     * Finds the end of a sentence. If a sentence ending period was found, returns the whole string
+     * up to and excluding that period. The end of sentence detection here could be replaced in the
+     * future by Java's built-in BreakIterator class.
+     *
+     * @param text The string to search.
+     * @param period The period character to find.
+     * @return The string up to and excluding the period, or null if no ending was found.
+     */
+    @Nullable
+    private static String findSentenceEndingOrNull(String text, String period) {
+        int periodIndex = text.indexOf(period);
+        String sentenceEnding = null;
+        while (periodIndex >= 0) {
+            final int afterPeriodIndex = periodIndex + period.length();
+
+            // Handle western period separately as it is only the end of a sentence if followed
+            // by whitespace. Other period characters often include whitespace in the character.
+            if (!DEFAULT_PERIOD.equals(period)
+                || afterPeriodIndex >= text.length()
+                || Character.isWhitespace(text.charAt(afterPeriodIndex))) {
+                sentenceEnding = text.substring(0, periodIndex);
                 break;
             }
-
-            result.append(text);
+            else {
+                periodIndex = text.indexOf(period, afterPeriodIndex);
+            }
         }
-        return result.toString();
+        return sentenceEnding;
     }
-
 }

src/main/resources/com/puppycrawl/tools/checkstyle/meta/checks/javadoc/SummaryJavadocCheck.xml

@@ -20,7 +20,10 @@
                <description>Specify the regexp for forbidden summary fragments.</description>
             </property>
             <property default-value="." name="period" type="java.lang.String">
-               <description>Specify the period symbol at the end of first javadoc sentence.</description>
+               <description>Specify the period symbol. Used to check the first sentence ends with a
+ period. Periods that are not followed by a whitespace character are ignored (eg. the period in
+ v1.0). Because some periods include whitespace built into the character, if this is set to a
+ non-default value any period will end the sentence, whether it is followed by whitespace or not.</description>
             </property>
             <property default-value="false"
                       name="violateExecutionOnNonTightHtml"

src/test/java/com/puppycrawl/tools/checkstyle/checks/javadoc/SummaryJavadocCheckTest.java

@@ -68,21 +68,22 @@ public void testInlineCorrect() throws Exception {
     @Test
     public void testIncorrect() throws Exception {
         final String[] expected = {
-            "24: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
-            "42: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
-            "47: " + getCheckMessage(MSG_SUMMARY_FIRST_SENTENCE),
-            "57: " + getCheckMessage(MSG_SUMMARY_JAVADOC),
-            "63: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
-            "68: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
-            "79: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
-            "93: " + getCheckMessage(MSG_SUMMARY_JAVADOC),
-            "113: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
-            "126: " + getCheckMessage(MSG_SUMMARY_FIRST_SENTENCE),
-            "131: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
-            "136: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
-            "142: " + getCheckMessage(MSG_SUMMARY_FIRST_SENTENCE),
-            "147: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
-            "150: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
+            "20: " + getCheckMessage(MSG_SUMMARY_FIRST_SENTENCE),
+            "25: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
+            "43: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
+            "48: " + getCheckMessage(MSG_SUMMARY_FIRST_SENTENCE),
+            "58: " + getCheckMessage(MSG_SUMMARY_JAVADOC),
+            "64: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
+            "69: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
+            "80: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
+            "94: " + getCheckMessage(MSG_SUMMARY_JAVADOC),
+            "114: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
+            "127: " + getCheckMessage(MSG_SUMMARY_FIRST_SENTENCE),
+            "132: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
+            "137: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
+            "143: " + getCheckMessage(MSG_SUMMARY_FIRST_SENTENCE),
+            "148: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
+            "151: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
         };
         verifyWithInlineConfigParser(
                 getPath("InputSummaryJavadocIncorrect.java"), expected);
@@ -130,19 +131,20 @@ public void testNoPeriod() throws Exception {
     @Test
     public void testDefaultConfiguration() throws Exception {
         final String[] expected = {
-            "23: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
-            "41: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
-            "46: " + getCheckMessage(MSG_SUMMARY_FIRST_SENTENCE),
-            "62: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
-            "67: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
-            "78: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
-            "112: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
-            "125: " + getCheckMessage(MSG_SUMMARY_FIRST_SENTENCE),
-            "130: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
-            "135: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
-            "141: " + getCheckMessage(MSG_SUMMARY_FIRST_SENTENCE),
-            "146: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
-            "149: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
+            "19: " + getCheckMessage(MSG_SUMMARY_FIRST_SENTENCE),
+            "24: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
+            "42: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
+            "47: " + getCheckMessage(MSG_SUMMARY_FIRST_SENTENCE),
+            "63: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
+            "68: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
+            "79: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
+            "113: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
+            "126: " + getCheckMessage(MSG_SUMMARY_FIRST_SENTENCE),
+            "131: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
+            "136: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
+            "142: " + getCheckMessage(MSG_SUMMARY_FIRST_SENTENCE),
+            "147: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
+            "150: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
         };
 
         verifyWithInlineConfigParser(
@@ -230,12 +232,31 @@ public void testPeriodAtEnd() throws Exception {
             "33: " + getCheckMessage(MSG_SUMMARY_JAVADOC_MISSING),
             "40: " + getCheckMessage(MSG_SUMMARY_FIRST_SENTENCE),
             "60: " + getCheckMessage(MSG_SUMMARY_FIRST_SENTENCE),
+            "70: " + getCheckMessage(MSG_SUMMARY_FIRST_SENTENCE),
         };
 
         verifyWithInlineConfigParser(
                 getPath("InputSummaryJavadocPeriodAtEnd.java"), expected);
     }
 
+    @Test
+    public void testForbiddenFragmentRelativeToPeriod() throws Exception {
+        final String[] expected = {
+            "23: " + getCheckMessage(MSG_SUMMARY_JAVADOC),
+        };
+
+        verifyWithInlineConfigParser(
+                getPath("InputSummaryJavadocForbiddenFragmentRelativeToPeriod.java"), expected);
+    }
+
+    @Test
+    public void testJapanesePeriod() throws Exception {
+        final String[] expected = CommonUtil.EMPTY_STRING_ARRAY;
+
+        verifyWithInlineConfigParser(
+                getPath("InputSummaryJavadocJapanesePeriod.java"), expected);
+    }
+
     @Test
     public void testHtmlFormatSummary() throws Exception {
         final String[] expected = {

src/test/resources/com/puppycrawl/tools/checkstyle/checks/javadoc/summaryjavadoc/InputSummaryJavadocForbiddenFragmentRelativeToPeriod.java

@@ -0,0 +1,28 @@
+/*
+SummaryJavadoc
+violateExecutionOnNonTightHtml = (default)false
+forbiddenSummaryFragments = ^$|fail-summary-fragment
+period = 。
+
+
+*/
+
+package com.puppycrawl.tools.checkstyle.checks.javadoc.summaryjavadoc;
+
+public class InputSummaryJavadocForbiddenFragmentRelativeToPeriod {
+
+    /**
+     * Summary sentence on its own line。
+     * <p>
+     * Another sentence that is not part of the summary,
+     * so this should not matter: fail-summary-fragment。
+     */
+    void foo1() {}
+
+    // violation below 'Forbidden summary fragment.'
+    /**
+     * Summary sentence containing default period mentioning version 1.1, then ending with correct
+     * period after disallowed words, fail-summary-fragment。
+     */
+    void foo2() {}
+}

src/test/resources/com/puppycrawl/tools/checkstyle/checks/javadoc/summaryjavadoc/InputSummaryJavadocIncorrect.java

@@ -16,6 +16,7 @@
  */
 class InputSummaryJavadocIncorrect {
 
+    // violation below 'First sentence .* missing an ending period.'
     /**
      * As of JDK 1.1, replaced by {@link #setBounds(int,int,int,int)}
      */

src/test/resources/com/puppycrawl/tools/checkstyle/checks/javadoc/summaryjavadoc/InputSummaryJavadocIncorrect2.java

@@ -15,6 +15,7 @@
  */
 class InputSummaryJavadocIncorrect2 {
 
+    // violation below 'First sentence .* missing an ending period.'
     /**
      * As of JDK 1.1, replaced by {@link #setBounds(int,int,int,int)}
      */

src/test/resources/com/puppycrawl/tools/checkstyle/checks/javadoc/summaryjavadoc/InputSummaryJavadocJapanesePeriod.java

@@ -0,0 +1,24 @@
+/*
+SummaryJavadoc
+violateExecutionOnNonTightHtml = (default)false
+forbiddenSummaryFragments = (default)^$
+period = 。
+
+
+*/
+
+package com.puppycrawl.tools.checkstyle.checks.javadoc.summaryjavadoc;
+
+public class InputSummaryJavadocJapanesePeriod {
+
+    /**
+     * Summary sentence ending with correct period and no following whitespace。The Japanese
+     * period has whitespace built in!
+     */
+    void foo1() {}
+
+    /**
+     * 要約文。別の文。
+     */
+    void foo2() {}
+}