apache#12901: add TestBackwardsCompatibility test case that reveals t…

…he block tree IntersectTermsEnum bug apache#12895

lucene/backward-codecs/src/test/org/apache/lucene/backward_index/TestBackwardsCompatibility.java

@@ -109,6 +109,7 @@
 import org.apache.lucene.search.SortField;
 import org.apache.lucene.search.TermQuery;
 import org.apache.lucene.search.TopDocs;
+import org.apache.lucene.search.WildcardQuery;
 import org.apache.lucene.store.ByteBuffersDirectory;
 import org.apache.lucene.store.Directory;
 import org.apache.lucene.store.FSDirectory;
@@ -2268,6 +2269,25 @@ public void testFailOpenOldIndex() throws IOException {
     }
   }
 
+  // #12895: test on a carefully crafted 9.8.0 index (from a small contiguous subset of wikibigall unique terms) that shows the read-time
+  // #exception of IntersectTermsEnum (used by WildcardQuery)
+  public void testWildcardQueryExceptions990() throws IOException {
+    Path path = createTempDir("12895");
+
+    String name = "index.12895.9.8.0.zip";
+    InputStream resource = TestBackwardsCompatibility.class.getResourceAsStream(name);
+    assertNotNull("missing zip file to reproduce #12895", resource);
+    TestUtil.unzip(resource, path);
+
+    try (Directory dir = newFSDirectory(path);
+         DirectoryReader reader = DirectoryReader.open(dir)) {
+      IndexSearcher searcher = new IndexSearcher(reader);
+
+      searcher.count(new WildcardQuery(new Term("field", "*qx*")));
+    }
+  }
+
+
   @Nightly
   public void testReadNMinusTwoCommit() throws IOException {
     for (String name : binarySupportedNames) {