[LUCENE-6385] NullPointerException from Highlighter.getBestFragment()

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 5.2
• Fix Version/s: 5.2, 6.0
• Component/s: modules/highlighter
• Lucene Fields: New, Patch Available
• Assignee: Robert Muir
• Reporter: Terry Smith
• Created: 01/Apr/15 14:18
• Updated: 28/Aug/22 14:29
• Resolved: 03/Apr/15 13:18

Description

When testing against the 5.1 nightly snapshots I've come across a NullPointerException in highlighting when nothing would be highlighted. This does not happen with 5.0.

java.lang.NullPointerException
	at __randomizedtesting.SeedInfo.seed([3EDC6EB0FA552B34:9971866E394F5FD0]:0)
	at org.apache.lucene.search.highlight.WeightedSpanTermExtractor.extractWeightedSpanTerms(WeightedSpanTermExtractor.java:311)
	at org.apache.lucene.search.highlight.WeightedSpanTermExtractor.extract(WeightedSpanTermExtractor.java:151)
	at org.apache.lucene.search.highlight.WeightedSpanTermExtractor.getWeightedSpanTerms(WeightedSpanTermExtractor.java:515)
	at org.apache.lucene.search.highlight.QueryScorer.initExtractor(QueryScorer.java:219)
	at org.apache.lucene.search.highlight.QueryScorer.init(QueryScorer.java:187)
	at org.apache.lucene.search.highlight.Highlighter.getBestTextFragments(Highlighter.java:196)
	at org.apache.lucene.search.highlight.Highlighter.getBestFragments(Highlighter.java:156)
	at org.apache.lucene.search.highlight.Highlighter.getBestFragment(Highlighter.java:102)
	at org.apache.lucene.search.highlight.Highlighter.getBestFragment(Highlighter.java:80)
	at org.apache.lucene.search.highlight.MissesTest.testPhraseQuery(MissesTest.java:50)

I've written a small unit test and used git bisect to narrow the regression to the following commit:

commit 24e4eefaefb1837d1d4fa35f7669c2b264f872ac
Author: Michael McCandless <[e-mail]>
Date:   Tue Mar 31 08:48:28 2015 +0000

    LUCENE-6308: cutover Spans to DISI, reuse ConjunctionDISI, use two-phased iteration
    
    git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_5x@1670273 13f79535-47bb-0310-9956-ffa450edef68

The problem looks quite simple, WeightedSpanTermExtractor.extractWeightedSpanTerms() needs an early return if SpanQuery.getSpans() returns null. All other callers check against this.

Unit test and fix (against the regressed commit) attached.