[GitHub] [lucene] janhoy commented on a change in pull request #84: LUCENE-9929 Make ScandinavianNormalizationFilter configurable wrt fol…

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janhoy commented on a change in pull request #84:
URL: https://github.com/apache/lucene/pull/84#discussion_r613595880



##########
File path: lucene/analysis/common/src/java/org/apache/lucene/analysis/miscellaneous/ScandinavianNormalizationFilter.java
##########
@@ -33,14 +34,45 @@
  * <p>blåbærsyltetøj == blåbärsyltetöj == blaabaarsyltetoej but not blabarsyltetoj räksmörgås ==
  * ræksmørgås == ræksmörgaos == raeksmoergaas but not raksmorgas
  *
+ * <p>You can choose which of the foldings to apply (aa, ao, ae, oe, oo) through a parameter.
+ *
  * @see ScandinavianFoldingFilter
  */
 public final class ScandinavianNormalizationFilter extends TokenFilter {
 
+  /**
+   * Create the filter with default folding rules, backward compatible with all earlier versions
+   *
+   * @param input the TokenStream
+   */
   public ScandinavianNormalizationFilter(TokenStream input) {
     super(input);
+    this.foldings = ALL_FOLDINGS;
   }
 
+  /**
+   * Create the filter using custom folding rules.
+   *
+   * @param input the TokenStream
+   * @param foldings a Set of Foldings to apply (i.e. AE, OE, AA, AO, OO)
+   */
+  public ScandinavianNormalizationFilter(TokenStream input, Set<Foldings> foldings) {

Review comment:
       We can obtain a similar Lucene API usability by adding helper vars:
   ```java
   public static final Set<Foldings> ALL_FOLDINGS = Set.of(AA, AO, OO, AE, OE);
   public static final Set<Foldings> NORWEGIAN_FOLDINGS = Set.of(AE, OE, AA);
   public static final Set<Foldings> DANISH_FOLDINGS = NORWEGIAN_FOLDINGS;
   public static final Set<Foldings> SWEDISH_FOLDINGS = ALL_FOLDINGS;
   ```
   In the factory that would translate to perhaps a "language" parameter with predefined settings.
   
   I'm not opposed to thin wrapper filters for each language, but I'd like some feedback from other Scandinavian users on what those should default to.




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