LUCENE-6657: don't throw NPE when a given segment never saw all terms used in the TAQ

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1689133 13f79535-47bb-0310-9956-ffa450edef68

lucene/sandbox/src/java/org/apache/lucene/search/TermAutomatonQuery.java

@@ -34,7 +34,6 @@ import org.apache.lucene.index.TermState;
 import org.apache.lucene.index.TermsEnum;
 import org.apache.lucene.search.similarities.Similarity;
 import org.apache.lucene.search.spans.SpanNearQuery;
-import org.apache.lucene.util.Bits;
 import org.apache.lucene.util.BytesRef;
 import org.apache.lucene.util.automaton.Automaton;
 import org.apache.lucene.util.automaton.Operations;
@@ -386,20 +385,25 @@ public class TermAutomatonQuery extends Query {
       // Initialize the enums; null for a given slot means that term didn't appear in this reader
       EnumAndScorer[] enums = new EnumAndScorer[idToTerm.size()];
 
+      boolean any = false;
       for(Map.Entry<Integer,TermContext> ent : termStates.entrySet()) {
         TermContext termContext = ent.getValue();
         assert termContext.topReaderContext == ReaderUtil.getTopLevelContext(context) : "The top-reader used to create Weight (" + termContext.topReaderContext + ") is not the same as the current reader's top-reader (" + ReaderUtil.getTopLevelContext(context);
         BytesRef term = idToTerm.get(ent.getKey());
         TermState state = termContext.get(context.ord);
         if (state != null) {
-
           TermsEnum termsEnum = context.reader().terms(field).iterator();
           termsEnum.seekExact(term, state);
           enums[ent.getKey()] = new EnumAndScorer(ent.getKey(), termsEnum.postings(null, PostingsEnum.POSITIONS));
+          any = true;
         }
       }
 
+      if (any) {
         return new TermAutomatonScorer(this, enums, anyTermID, idToTerm, similarity.simScorer(stats, context));
+      } else {
+        return null;
+      }
     }
     
     @Override

lucene/sandbox/src/test/org/apache/lucene/search/TestTermAutomatonQuery.java

@@ -738,4 +738,51 @@ public class TestTermAutomatonQuery extends LuceneTestCase {
     r.close();
     dir.close();
   }
+
+  public void testTermDoesNotExist() throws Exception {
+    Directory dir = newDirectory();
+    RandomIndexWriter w = new RandomIndexWriter(random(), dir);
+    Document doc = new Document();
+    doc.add(newTextField("field", "x y z", Field.Store.NO));
+    w.addDocument(doc);
+
+    IndexReader r = w.getReader();
+    IndexSearcher s = newSearcher(r);
+
+    TokenStream ts = new CannedTokenStream(new Token[] {
+        token("a", 1, 1),
+      });
+
+    TermAutomatonQuery q = new TokenStreamToTermAutomatonQuery().toQuery("field", ts);
+    // System.out.println("DOT: " + q.toDot());
+    assertEquals(0, s.search(q, 1).totalHits);
+
+    w.close();
+    r.close();
+    dir.close();
+  }
+
+  public void testOneTermDoesNotExist() throws Exception {
+    Directory dir = newDirectory();
+    RandomIndexWriter w = new RandomIndexWriter(random(), dir);
+    Document doc = new Document();
+    doc.add(newTextField("field", "x y z", Field.Store.NO));
+    w.addDocument(doc);
+
+    IndexReader r = w.getReader();
+    IndexSearcher s = newSearcher(r);
+
+    TokenStream ts = new CannedTokenStream(new Token[] {
+        token("a", 1, 1),
+        token("x", 1, 1),
+      });
+
+    TermAutomatonQuery q = new TokenStreamToTermAutomatonQuery().toQuery("field", ts);
+    // System.out.println("DOT: " + q.toDot());
+    assertEquals(0, s.search(q, 1).totalHits);
+
+    w.close();
+    r.close();
+    dir.close();
+  }
 }