QueryBuilder hands a token boost (BoostAttribute) above 1 or equal to 0 on a word that shares its position with a synonym straight to SynonymQuery, which throws IllegalArgumentException, so every query containing that word fails, while the same weight on a word without a synonym works
Finding LFV-588Area: core / util QueryBuilder token boosts on stacked tokens (newSynonymQuery; BoostAttribute from DelimitedBoostTokenFilter and weighted synonyms; reached through the classic and simple query parsers)Priority: lowImpact: wrong errorNovelty: new
AI-assisted finding, confirmed by automated checks, not yet triaged by a human Lucene committer. This site files nothing upstream.
What it shows
You configure weighted synonyms ('leopard, panthera|1.5') or let users type boosts ('leopard|2'), and expect QueryBuilder to apply the weight, as it does for a word without a synonym: 'lion => simba|1.5' gives (body:simba)^1.5 and 'tiger|2' gives (body:tiger)^2.0. But when the boosted token shares its position with another token, QueryBuilder.newSynonymQuery passes the raw boost to SynonymQuery.Builder.addTerm, which accepts only (0, 1], so building the query throws IllegalArgumentException 'boost must be a positive float between 0 (exclusive) and 1 (inclusive)' and QueryParser.parse('spotted leopard') fails with it instead of returning a query or a ParseException. Weights in (0, 1] work on both paths; whether 1.5 or 0 works depends only on whether the analyzer stacked the token.
The test shows that QueryBuilder throws when a weighted synonym (leopard, panthera|1.5 through SynonymGraphFilter then DelimitedBoostTokenFilter) gives a stacked token a boost above 1: newSynonymQuery passes the boost unchanged to SynonymQuery.Builder.addTerm, which accepts only (0, 1].
Expected vs actual
Expected: createBooleanQuery("body", "leopard") returns a query, as the same weight on an unstacked token gives a BoostQuery. Actual: IllegalArgumentException: boost must be a positive float between 0 (exclusive) and 1 (inclusive), with -ea and -da.
Files
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/analysis/common/build/libs/lucene-analysis-common-$V.jar
CP=$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.analysis.boost.TestStackedTokenBoostRangeGradle 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.