hunspell: disallow hidden title-case entries from compound middle/end (#12220)

if we only have custom-case uART and capitalized UART, we shouldn't accept StandUart as a compound (although we keep hidden "Uart" dictionary entries for internal purposes)

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

@@ -164,7 +164,7 @@ public class Hunspell {
   Root<CharsRef> findStem(
       char[] wordChars, int offset, int length, WordCase originalCase, WordContext context) {
     checkCanceled.run();
-    boolean checkCase = context != COMPOUND_MIDDLE && context != COMPOUND_END;
+    WordCase toCheck = context != COMPOUND_MIDDLE && context != COMPOUND_END ? originalCase : null;
     @SuppressWarnings({"rawtypes", "unchecked"})
     Root<CharsRef>[] result = new Root[1];
     stemmer.doStem(
@@ -173,7 +173,7 @@ public class Hunspell {
         length,
         context,
         (stem, formID, morphDataId, outerPrefix, innerPrefix, outerSuffix, innerSuffix) -> {
-          if (checkCase && !acceptCase(originalCase, formID, stem)) {
+          if (!acceptCase(toCheck, formID, stem)) {
             return dictionary.hasFlag(formID, Dictionary.HIDDEN_FLAG);
           }
           if (acceptsStem(formID)) {

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

@@ -205,6 +205,10 @@ public class TestSpellChecking extends LuceneTestCase {
     doTest("germancompounding");
   }
 
+  public void testGermanManualCase() throws Exception {
+    doTest("germanManualCase");
+  }
+
   public void testApplyOconvToSuggestions() throws Exception {
     doTest("oconv");
   }

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

@@ -0,0 +1,51 @@
+# no CHECKCOMPOUNDCASE
+
+# compound flags
+
+COMPOUNDBEGIN U
+COMPOUNDMIDDLE V
+COMPOUNDEND W
+
+ONLYINCOMPOUND X
+COMPOUNDPERMITFLAG P
+
+COMPOUNDMIN 1
+WORDCHARS -
+
+# dash prefix for compounds with dash (Arbeits-Computer)
+
+PFX - Y 1
+PFX - 0 -/P .
+
+# decapitalizing prefix
+
+PFX D Y 29
+PFX D A a/PX A
+PFX D <20> <20>/PX <20>
+PFX D B b/PX B
+PFX D C c/PX C
+PFX D D d/PX D
+PFX D E e/PX E
+PFX D F f/PX F
+PFX D G g/PX G
+PFX D H h/PX H
+PFX D I i/PX I
+PFX D J j/PX J
+PFX D K k/PX K
+PFX D L l/PX L
+PFX D M m/PX M
+PFX D N n/PX N
+PFX D O o/PX O
+PFX D <20> <20>/PX <20>
+PFX D P p/PX P
+PFX D Q q/PX Q
+PFX D R r/PX R
+PFX D S s/PX S
+PFX D T t/PX T
+PFX D U u/PX U
+PFX D <20> <20>/PX <20>
+PFX D V v/PX V
+PFX D W w/PX W
+PFX D X x/PX X
+PFX D Y y/PX Y
+PFX D Z z/PX Z

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

@@ -0,0 +1,5 @@
+4
+uART/XW-
+bein/XW-
+Stand/UX
+UART/-

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

@@ -0,0 +1,3 @@
+UART
+Standbein
+Stand-uART

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

@@ -0,0 +1,3 @@
+StandUart
+uART
+Uart