LeafCollector's class javadoc example ('collect docIDs into a BitSet') does not compile on any release since 5.1.0: its anonymous Collector has no scoreMode() (the abstract needsScores() before 8.0.0) and its setScorer(Scorer) does not implement LeafCollector.setScorer(Scorable) (documentation defect)

Finding LFV-1018Area: core / search (LeafCollector class javadoc example)Priority: lowImpact: minorNovelty: new

AI-assisted finding, confirmed by automated checks, not yet triaged by a human Lucene committer. This site files nothing upstream.

What it shows

The LeafCollector class javadoc explains that collect() receives segment-relative doc IDs and shows 'a simple example showing how to collect docIDs into a BitSet' with an anonymous Collector and LeafCollector. Copied into code on any current release it does not compile: the anonymous Collector does not implement the abstract scoreMode() (needsScores() from 5.1.0 to 7.x), and the anonymous LeafCollector does not implement setScorer(Scorable), because the example's setScorer(Scorer) has only been an overload since 8.0.0. With scoreMode() returning ScoreMode.COMPLETE_NO_SCORES and a Scorable parameter the example compiles and collects exactly the expected global doc IDs, so only the javadoc is wrong.

Expected vs actual

Expected: The example compiles, as it did on 5.0.0 and as the corrected example does on main.
Actual: javac reports 2 errors: <anonymous Example$1> does not override abstract method scoreMode() in Collector, and <anonymous Example$1$1> does not override abstract method setScorer(Scorable) in LeafCollector; the same with assertions off.

Files

src/org/apache/lucene/search/TestLeafCollectorJavadocExample.java (JUnit test)

Run it

Tested on Lucene main e1faeba08bde (2026-11-02): still reproduces.
Tested on Lucene main 645d4fe14a20 (2026-10-28): reproduced.
How to read the outcome: a failing test is the finding reproducing (the failure message states expected against actual).
Seeds: a rerun with the same seed replays the same random choices. Assertions off (-da -dsa -Dtests.asserts=false) is the production-like setting.

# Lucene checkout at the tested commit, built with: ./gradlew --no-daemon assemble   (JDK 25)
LUCENE=/path/to/lucene; V=12.0.0-SNAPSHOT
CP=$LUCENE/lucene/core/build/libs/lucene-core-$V.jar
CP=$CP:$LUCENE/lucene/codecs/build/libs/lucene-codecs-$V.jar
CP=$CP:$LUCENE/lucene/test-framework/build/libs/lucene-test-framework-$V.jar
CP=$CP:randomizedtesting-runner-2.9.2.jar:junit-4.13.2.jar:hamcrest-3.0.jar   # test-framework dependencies (Maven Central)
CP=$CP:junit-platform-console-standalone-6.1.3.jar   # JUnit Platform console launcher (Maven Central)

javac -d classes -cp "$CP" $(find src -name '*.java')

# run 1: assertions on, seed DEADBEEF
java -ea -esa --add-modules jdk.incubator.vector --enable-native-access=ALL-UNNAMED -Dtests.seed=DEADBEEF \
     -cp "classes:$CP" org.junit.platform.console.ConsoleLauncher \
     execute --select-class org.apache.lucene.search.TestLeafCollectorJavadocExample

Gradle alternative: copy the test into the matching module's src/test/ tree of the checkout and run ./gradlew -p lucene/<module> test --tests <class> -Ptests.seed=<seed> (add -Ptests.asserts=false for a run without assertions).

Files shown on the finding page

TestLeafCollectorJavadocExample.java

Feedback

Open an issue in lucene-ai-bug-hunt. Please do not open issues or pull requests in apache/lucene about this finding unless a Lucene committer agrees it should be filed.

Snapshot of 2026-11-04. AI-assisted; not yet triaged by a human Lucene committer. Feedback: open an issue in lucene-ai-bug-hunt.