LUCENE-9853: Use CJKWidthCharFilter as the default character width normalizer in JapaneseAnalyzer (#26)

lucene/CHANGES.txt

@@ -95,6 +95,9 @@ API Changes
 * LUCENE-9796: SortedDocValues no longer extends BinaryDocValues, as binaryValue() was not performant.
   See MIGRATE.md for details. (Robert Muir)
 
+* LUCENE-9853: JapaneseAnalyzer should use CJKWidthCharFilter for full-width and half-width character normalization.
+  (Tomoko Uchida)
+
 Improvements
 
 * LUCENE-9687: Hunspell support improvements: add API for spell-checking and suggestions, support compound words,

lucene/analysis/kuromoji/src/java/org/apache/lucene/analysis/ja/JapaneseAnalyzer.java

@@ -17,6 +17,7 @@
 package org.apache.lucene.analysis.ja;
 
 import java.io.IOException;
+import java.io.Reader;
 import java.util.HashSet;
 import java.util.Set;
 import org.apache.lucene.analysis.CharArraySet;
@@ -25,7 +26,7 @@ import org.apache.lucene.analysis.StopFilter;
 import org.apache.lucene.analysis.StopwordAnalyzerBase;
 import org.apache.lucene.analysis.TokenStream;
 import org.apache.lucene.analysis.Tokenizer;
-import org.apache.lucene.analysis.cjk.CJKWidthFilter;
+import org.apache.lucene.analysis.cjk.CJKWidthCharFilter;
 import org.apache.lucene.analysis.ja.JapaneseTokenizer.Mode;
 import org.apache.lucene.analysis.ja.dict.UserDictionary;
 
@@ -95,7 +96,6 @@ public class JapaneseAnalyzer extends StopwordAnalyzerBase {
     Tokenizer tokenizer = new JapaneseTokenizer(userDict, true, true, mode);
     TokenStream stream = new JapaneseBaseFormFilter(tokenizer);
     stream = new JapanesePartOfSpeechStopFilter(stream, stoptags);
-    stream = new CJKWidthFilter(stream);
     stream = new StopFilter(stream, stopwords);
     stream = new JapaneseKatakanaStemFilter(stream);
     stream = new LowerCaseFilter(stream);
@@ -104,8 +104,17 @@ public class JapaneseAnalyzer extends StopwordAnalyzerBase {
 
   @Override
   protected TokenStream normalize(String fieldName, TokenStream in) {
-    TokenStream result = new CJKWidthFilter(in);
-    result = new LowerCaseFilter(result);
+    TokenStream result = new LowerCaseFilter(in);
     return result;
   }
+
+  @Override
+  protected Reader initReader(String fieldName, Reader reader) {
+    return new CJKWidthCharFilter(reader);
+  }
+
+  @Override
+  protected Reader initReaderForNormalization(String fieldName, Reader reader) {
+    return new CJKWidthCharFilter(reader);
+  }
 }

lucene/analysis/kuromoji/src/test/org/apache/lucene/analysis/ja/TestJapaneseAnalyzer.java

@@ -146,6 +146,22 @@ public class TestJapaneseAnalyzer extends BaseTokenStreamTestCase {
     a.close();
   }
 
+  public void testCharWidthNormalization() throws Exception {
+    final Analyzer a =
+        new JapaneseAnalyzer(
+            TestJapaneseTokenizer.readDict(),
+            Mode.SEARCH,
+            JapaneseAnalyzer.getDefaultStopSet(),
+            JapaneseAnalyzer.getDefaultStopTags());
+    assertTokenStreamContents(
+        a.tokenStream("foo", "新橋６－２０－１"),
+        new String[] {"新橋", "6", "20", "1"},
+        new int[] {0, 2, 4, 7},
+        new int[] {2, 3, 6, 8},
+        8);
+    a.close();
+  }
+
   // LUCENE-3897: this string (found by running all jawiki
   // XML through JapaneseAnalyzer) caused AIOOBE
   public void testCuriousString() throws Exception {