luozhuang opened a new issue, #12991:
URL: https://github.com/apache/lucene/issues/12991
### Description
I encountered a NullPointerException when I searched with SpanfirstQuery.
The Lucene version is 8.10.
The example call stack is
```
A Java Exception: java.lang.NullPointerException
at #1
org.apache.lucene.search.spans.SpanScorer.scoreCurrentDoc(SpanScorer.java:76)
#2 org.apache.lucene.search.spans.SpanScorer.score(SpanScorer.java:134)
#3
com.dummy.search.mySearcher.DocScoreCollector.collect(MyDocScoreCollector.java:59)
#4
com.dummy.search.mySearcher.DocScoreCollector$1.collect(MyDocScoreCollector.java:108)
#5
org.apache.lucene.search.Weight$DefaultBulkScorer.scoreAll(Weight.java:283)
#6 org.apache.lucene.search.Weight$DefaultBulkScorer.score(Weight.java:232)
#7 org.apache.lucene.search.BulkScorer.score(BulkScorer.java:39)
#8 org.apache.lucene.search.IndexSearcher.search(IndexSearcher.java:659)
#9 org.apache.lucene.search.IndexSearcher.search(IndexSearcher.java:443)
```
The frames #3 and #4 are within my customized collector. This collector has
a SpanScorer. The example code of this class looks like
```
public class MyDocScoreCollector implements Collector {
ScoreMode collectScore;
Scorable scorer;
ArrayList<ScoreDoc> scoreDocs = new ArrayList<ScoreDoc>(100);
int docBase;
public MyDocScoreCollector(boolean collectScore) {
if (collectScore) {
this.collectScore = ScoreMode.COMPLETE;
}
else {
this.collectScore = ScoreMode.COMPLETE_NO_SCORES;
}
}
public void collect(int doc) throws IOException {
float score = 0.0f;
if(collectScore==ScoreMode.COMPLETE)
score = scorer.score();
ScoreDoc sd = new ScoreDoc(docBase + doc, score);
scoreDocs.add(sd);
}
public void setScorer(Scorable scorer) throws IOException {
this.scorer = scorer;
}
@Override
public ScoreMode scoreMode() {
return ScoreMode.COMPLETE_NO_SCORES;
}
public void setNextReader(LeafReaderContext context) throws IOException
{
this.docBase = context.docBase;
}
abstract static class ScorerLeafCollector implements LeafCollector {
public MyDocScoreCollector docScoreCollector = null;
@Override
public void setScorer(Scorable scorer) throws IOException {
docScoreCollector.setScorer(scorer);
}
ScorerLeafCollector(MyDocScoreCollector collector) {
this.docScoreCollector = collector;
}
}
@Override
public LeafCollector getLeafCollector(LeafReaderContext context) throws
IOException {
docBase = context.docBase;
return new ScorerLeafCollector(this) {
@Override
public void setScorer(Scorable scorer) throws IOException {
super.setScorer(scorer);
}
@Override
public void collect(int doc) throws IOException {
docScoreCollector.collect(doc);
}
};
}
}
```
I found the NullPointerException is caused by the empty **SimScorer** on
**SpanWeight**.
Due to the empty **SimScorer** on **SpanWeight**, when getting a
**SpanScorer** from it, it returns a **SpanScorer** with a null
**LeafSimScorer**. Finally, when scoring the doc with the SpanScorer, it
encounters the NullPointerException.
Within the method SpanScorer.scoreCurrentDoc(), it doesn't check if the
**LeafSimScorer** field is null. Instead, only an assertion is there.
I also found there is another [similar issue
](https://github.com/apache/lucene/issues/10564)related to the empty
**SimScorer** on **SpanWeight**. But it has been fixed by adding some
defensive code.
Seems this is another similar case.
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