QueryNodeProcessorPipeline's listIterator()/subList() views, and replaceAll / Collections.replaceAll built on them, put processors on the pipeline without its QueryConfigHandler, so the flexible query parser silently skips point, boost and default phrase slop handling or throws NullPointerException

Finding LFV-966Area: queryparser / flexible core: QueryNodeProcessorPipeline (java.util.List views and default methods)Priority: lowImpact: silent wrong resultsNovelty: new

Finding page for LFV-966

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

What it shows

You customise a flexible query parser pipeline, for example StandardQueryParser's, by inserting or replacing a processor through the pipeline's java.util.List API: pipeline.listIterator() then add or set, subList(..).set, pipeline.replaceAll or Collections.replaceAll. You expect the processor to receive the pipeline's QueryConfigHandler, as it does with add(k, p) or set(k, p), because the class says it 'takes care of setting this QueryConfigHandler on all processor on pipeline'. Instead those paths write through the private ArrayList's own views and leave the processor with a null handler, so a replaced PointQueryNodeProcessor turns n:5 into a TermQuery that finds 0 of 1 matching documents, a replaced BoostQueryNodeProcessor drops field boosts, and most other stock processors throw NullPointerException at parse.

The test shows that a processor put on a QueryNodeProcessorPipeline through its listIterator() (here replacing StandardQueryParser's PointQueryNodeProcessor with ListIterator.set) never gets the pipeline's QueryConfigHandler, unlike pipeline.set(k, p).

Expected vs actual

Expected n:5 (a field with a PointsConfig) to parse to a PointRangeQuery; actual: TermQuery n:5 (expected a PointRangeQuery, got org.apache.lucene.search.TermQuery n:5), with -ea and -da.

Files

src/org/apache/lucene/queryparser/flexible/core/processors/TestPipelineListIteratorSetConfigHandler.java (JUnit test)

Run it

Tested on Lucene main e1faeba08bde (2026-11-02): still reproduces.
Tested on Lucene main 645d4fe14a20 (2026-10-28): reproduced.
Recorded outcome of run 1 on Lucene main 645d4fe14a20: 1 test(s) run, 1 failed.
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=$CP:$LUCENE/lucene/facet/build/libs/lucene-facet-$V.jar
CP=$CP:$LUCENE/lucene/queries/build/libs/lucene-queries-$V.jar
CP=$CP:$LUCENE/lucene/queryparser/build/libs/lucene-queryparser-$V.jar
CP=$CP:$LUCENE/lucene/sandbox/build/libs/lucene-sandbox-$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.queryparser.flexible.core.processors.TestPipelineListIteratorSetConfigHandler

The module(s) facet also need their third-party runtime jars; ./gradlew -p lucene/<module> dependencies lists them.

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).

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.