LUCENE-6093: don't throw NPE when BlendedInfixSuggester.lookup doesn't have a prefix token

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1656173 13f79535-47bb-0310-9956-ffa450edef68

lucene/CHANGES.txt

@@ -484,6 +484,10 @@ Bug Fixes
   high frequency terms in extremely large indices (Robert Muir, Mike
   McCandless)
 
+* LUCENE-6093: Don't throw NullPointerException from
+  BlendedInfixSuggester for lookups that do not end in a prefix
+  token.  (jane chang via Mike McCandless)
+
 Documentation
 
 * LUCENE-5392: Add/improve analysis package documentation to reflect

lucene/suggest/src/java/org/apache/lucene/search/suggest/analyzing/AnalyzingInfixSuggester.java

@@ -576,7 +576,11 @@ public class AnalyzingInfixSuggester extends Lookup implements Closeable {
 
   /**
    * Create the results based on the search hits.
-   * Can be overridden by subclass to add particular behavior (e.g. weight transformation)
+   * Can be overridden by subclass to add particular behavior (e.g. weight transformation).
+   * Note that there is no prefix toke (the {@code prefixToken} argument will
+   * be null) whenever the final token in the incoming request was in fact finished
+   * (had trailing characters, such as white-space).
+   *
    * @throws IOException If there are problems reading fields from the underlying Lucene index.
    */
   protected List<LookupResult> createResults(IndexSearcher searcher, TopFieldDocs hits, int num,

lucene/suggest/src/java/org/apache/lucene/search/suggest/analyzing/BlendedInfixSuggester.java

@@ -261,7 +261,7 @@ public class BlendedInfixSuggester extends AnalyzingInfixSuggester {
 
       String docTerm = term.utf8ToString();
 
-      if (matchedTokens.contains(docTerm) || docTerm.startsWith(prefixToken)) {
+      if (matchedTokens.contains(docTerm) || (prefixToken != null && docTerm.startsWith(prefixToken))) {
  
         DocsAndPositionsEnum docPosEnum = it.docsAndPositions(null, null, DocsAndPositionsEnum.FLAG_OFFSETS);
         docPosEnum.nextDoc();

lucene/suggest/src/test/org/apache/lucene/search/suggest/analyzing/BlendedInfixSuggesterTest.java

@@ -165,6 +165,33 @@ public class BlendedInfixSuggesterTest extends LuceneTestCase {
     suggester.close();
   }
 
+  /**
+   * Handle trailing spaces that result in no prefix token LUCENE-6093
+   */
+  public void testNullPrefixToken() throws IOException {
+
+    BytesRef payload = new BytesRef("lake");
+
+    Input keys[] = new Input[]{
+        new Input("top of the lake", 8, payload)
+    };
+
+    Path tempDir = createTempDir("BlendedInfixSuggesterTest");
+
+    Analyzer a = new StandardAnalyzer(CharArraySet.EMPTY_SET);
+    BlendedInfixSuggester suggester = new BlendedInfixSuggester(newFSDirectory(tempDir), a, a,
+                                                                AnalyzingInfixSuggester.DEFAULT_MIN_PREFIX_CHARS,
+                                                                BlendedInfixSuggester.BlenderType.POSITION_LINEAR,
+                                                                BlendedInfixSuggester.DEFAULT_NUM_FACTOR, false);
+    suggester.build(new InputArrayIterator(keys));
+
+    getInResults(suggester, "of ", payload, 1);
+    getInResults(suggester, "the ", payload, 1);
+    getInResults(suggester, "lake ", payload, 1);
+
+    suggester.close();
+  }
+
   public void /*testT*/rying() throws IOException {
 
     BytesRef lake = new BytesRef("lake");