LUCENE-8305: ComplexPhraseQuery.rewrite now handles an embedded MultiTermQuery

that rewrites to a MatchNoDocsQuery instead of throwing an exception.
Fixes #258
Fixes #327

lucene/CHANGES.txt

@@ -198,6 +198,10 @@ Bug Fixes
 * LUCENE-8244: Do not leak open file descriptors in SearcherTaxonomyManager's
   refresh on exception (Mike McCandless)
 
+* LUCENE-8305: ComplexPhraseQuery.rewrite now handles an embedded MultiTermQuery
+  that rewrites to a MatchNoDocsQuery instead of throwing an exception.
+  (Bjarke Mortensen, Andy Tran via David Smiley)
+
 Other
 
 * LUCENE-8301: Update randomizedtesting to 2.6.0. (Dawid Weiss)

lucene/queryparser/src/java/org/apache/lucene/queryparser/complexPhrase/ComplexPhraseQueryParser.java

@@ -398,6 +398,13 @@ public class ComplexPhraseQueryParser extends QueryParser {
         } else if (childQuery instanceof BooleanQuery) {
           BooleanQuery cbq = (BooleanQuery) childQuery;
           addComplexPhraseClause(chosenList, cbq);
+        } else if (childQuery instanceof MatchNoDocsQuery) {
+          // Insert fake term e.g. phrase query was for "Fred Smithe*" and
+          // there were no "Smithe*" terms - need to
+          // prevent match on just "Fred".
+          SpanQuery stq = new SpanTermQuery(new Term(field,
+                                                     "Dummy clause because no terms found - must match nothing"));
+          chosenList.add(stq);
         } else {
           // TODO alternatively could call extract terms here?
           throw new IllegalArgumentException("Unknown query type:"

lucene/queryparser/src/test/org/apache/lucene/queryparser/complexPhrase/TestComplexPhraseQuery.java

@@ -64,6 +64,8 @@ public class TestComplexPhraseQuery extends LuceneTestCase {
     checkMatches("\"john\"", "1,3"); // Simple single-term still works
     checkMatches("\"(john OR johathon)  smith\"", "1,2"); // boolean logic with
     // brackets works.
+    checkMatches("\"(john OR nosuchword*)  smith\"", "1"); // boolean logic with
+    // brackets works when one of the terms in BooleanQuery does not exist (LUCENE-8305).
     checkMatches("\"(jo* -john) smyth~\"", "2"); // boolean logic with
     // brackets works.