LUCENE-10312: Make stemming configurable on PersianAnalyzer

lucene/analysis/common/src/java/org/apache/lucene/analysis/fa/PersianAnalyzer.java

@@ -88,30 +88,43 @@ private static class DefaultSetHolder {
   }
 
   private final CharArraySet stemExclusionSet;
+  private final boolean useStemming;
 
   /** Builds an analyzer with the default stop words: {@link #DEFAULT_STOPWORD_FILE}. */
   public PersianAnalyzer() {
     this(DefaultSetHolder.DEFAULT_STOP_SET);
   }
 
   /**
-   * Builds an analyzer with the given stop words
+   * Builds an analyzer with the default stop words: {@link #DEFAULT_STOPWORD_FILE}
+   *
+   * @param useStemming whether or not to enable stemming
+   */
+  public PersianAnalyzer(boolean useStemming) {
+    this(DefaultSetHolder.DEFAULT_STOP_SET, useStemming, CharArraySet.EMPTY_SET);
+  }
+
+  /**
+   * Builds an analyzer with the given stop words and no stemming
    *
    * @param stopwords a stopword set
    */
   public PersianAnalyzer(CharArraySet stopwords) {
-    this(stopwords, CharArraySet.EMPTY_SET);
+    this(stopwords, false, CharArraySet.EMPTY_SET);
   }
 
   /**
-   * Builds an analyzer with the given stop word. If a none-empty stem exclusion set is provided
-   * this analyzer will add a {@link SetKeywordMarkerFilter} before {@link PersianStemFilter}.
+   * Builds an analyzer with the given stop word. If a non-empty stem exclusion set is provided this
+   * analyzer will add a {@link SetKeywordMarkerFilter} before {@link PersianStemFilter}.
    *
    * @param stopwords a stopword set
+   * @param useStemming whether or not to enable stemming
    * @param stemExclusionSet a set of terms not to be stemmed
    */
-  public PersianAnalyzer(CharArraySet stopwords, CharArraySet stemExclusionSet) {
+  public PersianAnalyzer(
+      CharArraySet stopwords, boolean useStemming, CharArraySet stemExclusionSet) {
     super(stopwords);
+    this.useStemming = useStemming;
     this.stemExclusionSet = CharArraySet.unmodifiableSet(CharArraySet.copy(stemExclusionSet));
   }
 
@@ -140,7 +153,10 @@ protected TokenStreamComponents createComponents(String fieldName) {
     if (!stemExclusionSet.isEmpty()) {
       result = new SetKeywordMarkerFilter(result, stemExclusionSet);
     }
-    return new TokenStreamComponents(source, new PersianStemFilter(result));
+    if (useStemming) {
+      result = new PersianStemFilter(result);
+    }
+    return new TokenStreamComponents(source, result);
   }
 
   @Override

lucene/analysis/common/src/test/org/apache/lucene/analysis/fa/TestPersianAnalyzer.java

@@ -227,4 +227,15 @@ public void testRandomStrings() throws Exception {
     checkRandomData(random(), a, 200 * RANDOM_MULTIPLIER);
     a.close();
   }
+
+  public void testStemming() throws Exception {
+    {
+      PersianAnalyzer a = new PersianAnalyzer();
+      checkOneTerm(a, "دوستان", "دوستان");
+    }
+    {
+      PersianAnalyzer a = new PersianAnalyzer(true);
+      checkOneTerm(a, "دوستان", "دوست");
+    }
+  }
 }

lucene/analysis/common/src/test/org/apache/lucene/analysis/fa/TestPersianStemFilter.java

@@ -32,7 +32,7 @@ public class TestPersianStemFilter extends BaseTokenStreamTestCase {
   @Override
   public void setUp() throws Exception {
     super.setUp();
-    a = new PersianAnalyzer();
+    a = new PersianAnalyzer(true);
   }
 
   @Override