Hunspell getAllWordForms, generateAllSimpleWords and compress never generate a suffix that only a prefix's continuation class allows: with ampere/U and 'PFX U 0 kilo/S', spell() accepts amperes and kiloamperes, but getAllWordForms("ampere") returns only [ampere, kiloampere]
Finding LFV-634Area: analysis / hunspell (WordFormGenerator: getAllWordForms, generateAllSimpleWords, compress)Priority: lowImpact: 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 load a Hunspell dictionary in which a prefix rule's continuation class allows a suffix, for example 'PFX U 0 kilo/S' and 'SFX S 0 s' with the entry ampere/U, and ask Hunspell.getAllWordForms("ampere") for all forms of that entry. You expect ampere, amperes, kiloampere and kiloamperes: Lucene's own spell() accepts all four and analyzeSimpleWord() analyses each one as a form of ampere/U, as C Hunspell 1.7.2 also does. Instead you get only [ampere, kiloampere], because WordFormGenerator applies suffixes only from the entry's own flags and then forbids any suffix once a prefix has been applied (WordFormGenerator.java:378); generateAllSimpleWords misses the same words, and compress() suggests an unneeded flag (for work/P with 'PFX P 0 re/S', compress([work, rework, reworks]) proposes work/PS, which also adds the unrequested word works).
The test shows that Hunspell getAllWordForms never generates a suffix that only a prefix's continuation class allows (PFX U 0 kilo/S, SFX S 0 s, entry ampere/U), although spell("kiloamperes") accepts it.
Expected vs actual
Expected [ampere, kiloampere, kiloamperes]; actual [ampere, kiloampere], 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.hunspell.TestWordFormsPrefixEnabledSuffixGradle 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).
Formal models and scripts this finding's part of the hunt used: hunspell-wordform-generator-munch-differential
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.