LUCENE-9681: Hunspell spellchecker: support numbers with separators (#2224)

lucene/analysis/common/src/java/org/apache/lucene/analysis/hunspell/SpellChecker.java

@@ -35,11 +35,17 @@ public class SpellChecker {
 
   /** @return whether the given word's spelling is considered correct according to Hunspell rules */
   public boolean spell(String word) {
+    if (word.isEmpty()) return true;
+
     char[] wordChars = word.toCharArray();
     if (dictionary.isForbiddenWord(wordChars, scratch)) {
       return false;
     }
 
+    if (isNumber(word)) {
+      return true;
+    }
+
     if (!stemmer.stem(wordChars, word.length()).isEmpty()) {
       return true;
     }
@@ -51,6 +57,28 @@ public class SpellChecker {
     return false;
   }
 
+  private static boolean isNumber(String s) {
+    int i = 0;
+    while (i < s.length()) {
+      char c = s.charAt(i);
+      if (isDigit(c)) {
+        i++;
+      } else if (c == '.' || c == ',' || c == '-') {
+        if (i == 0 || i >= s.length() - 1 || !isDigit(s.charAt(i + 1))) {
+          return false;
+        }
+        i += 2;
+      } else {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  private static boolean isDigit(char c) {
+    return c >= '0' && c <= '9';
+  }
+
   private boolean tryBreaks(String word) {
     for (String br : dictionary.breaks.starting) {
       if (word.length() > br.length() && word.startsWith(br)) {

lucene/analysis/common/src/test/org/apache/lucene/analysis/hunspell/SpellCheckerTest.java

@@ -23,8 +23,13 @@ import java.nio.file.Path;
 import java.util.Objects;
 import org.apache.lucene.store.ByteBuffersDirectory;
 import org.apache.lucene.util.IOUtils;
+import org.junit.Test;
 
 public class SpellCheckerTest extends StemmerTestBase {
+  @Test
+  public void i53643_numbersWithSeparators() throws Exception {
+    doTest("i53643");
+  }
 
   public void testBreak() throws Exception {
     doTest("break");

lucene/analysis/common/src/test/org/apache/lucene/analysis/hunspell/i53643.aff

@@ -0,0 +1,2 @@
+# check numbers with separators
+WORDCHARS 0123456789.-,

lucene/analysis/common/src/test/org/apache/lucene/analysis/hunspell/i53643.dic

@@ -0,0 +1,2 @@
+1
+foo

lucene/analysis/common/src/test/org/apache/lucene/analysis/hunspell/i53643.good

@@ -0,0 +1,21 @@
+1
+12
+123
+1234
+12345
+123456
+1234567
+1.1
+1.12
+1.123
+1.1234
+1.12345
+1.123456
+12.1
+123.12
+1234.123
+12345.1234
+123456.12345
+1234567.123456
+4,2
+42-42

lucene/analysis/common/src/test/org/apache/lucene/analysis/hunspell/i53643.wrong

@@ -0,0 +1,4 @@
+1..2
+1,,2
+1.,2
+1,.2