LUCENE-9702: Hunspell: support alternate casing for short language codes (#2253)

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

@@ -374,7 +374,9 @@ public class Dictionary {
         fullStrip = true;
       } else if ("LANG".equals(firstWord)) {
         language = singleArgument(reader, line);
-        alternateCasing = "tr_TR".equals(language) || "az_AZ".equals(language);
+        int underscore = language.indexOf("_");
+        String langCode = underscore < 0 ? language : language.substring(0, underscore);
+        alternateCasing = langCode.equals("tr") || langCode.equals("az");
       } else if ("BREAK".equals(firstWord)) {
         breaks = parseBreaks(reader, line);
       } else if ("FORBIDDENWORD".equals(firstWord)) {

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

@@ -56,6 +56,11 @@ public class SpellCheckerTest extends StemmerTestBase {
     doTest("i53643");
   }
 
+  @Test
+  public void dotless_i() throws Exception {
+    doTest("dotless_i");
+  }
+
   @Test
   public void needAffixOnAffixes() throws Exception {
     doTest("needaffix5");

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

@@ -0,0 +1,2 @@
+SET UTF-8
+LANG tr

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

@@ -0,0 +1,4 @@
+3
+iç
+ışık
+Diyarbakır

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

@@ -0,0 +1,8 @@
+Diyarbakır
+DİYARBAKIR
+iç
+İç
+ışık
+Işık
+İÇ
+IŞIK

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

@@ -0,0 +1,6 @@
+Diyarbakir
+DIYARBAKIR
+Iç
+İşık
+IÇ
+İŞIK