WordDelimiterGraphFilter with IGNORE_KEYWORDS moves the position hole of a swallowed delimiter-only token (a standalone '/', '-' or '&') to after the next keyword token, so exact phrases across the keyword miss or over-match (released since 7.4.0)
Finding LFV-353Area: analysis / WordDelimiterGraphFilter position increments (IGNORE_KEYWORDS keyword bypass; factory ignoreKeywords option)Priority: mediumImpact: silent wrong resultsNovelty: 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 analyze 'lucene / solr rocks' with a whitespace tokenizer, a keyword marker that marks 'solr', and WordDelimiterGraphFilter(GENERATE_WORD_PARTS | IGNORE_KEYWORDS), and expect the hole left by the swallowed '/' to stay in front of 'solr' (position increments {1, 2, 1}), exactly as when 'solr' is not a keyword, is marked without IGNORE_KEYWORDS, or is a protected word. Instead the keyword branch returns 'solr' before the pending increment is applied, so 'solr' gets 1 and 'rocks' gets 2 ({1, 1, 2}); with the same analyzer at index and query time the exact phrase "solr rocks" finds 0 of the 1 matching documents, and the phrase "lucene solr" matches the document 'lucene / solr', which the chain without the keyword mark does not.
The test shows that with IGNORE_KEYWORDS, WordDelimiterGraphFilter returns a keyword token before applying the hole left by a swallowed delimiter-only token, so the hole moves to after the keyword.
Expected vs actual
Expected position increments for lucene / solr rocks with solr marked as a keyword: {1, 2, 1}. Actual: {1, 1, 2} (posIncrement 1 term=solr expected:<2> but was:<1>, 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.miscellaneous.TestWdgfIgnoreKeywordsHoleGradle 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.