Hunspell Dictionary throws NullPointerException instead of a parse error when a REP, MAP, ICONV/OCONV, COMPOUNDRULE, BREAK or CHECKCOMPOUNDPATTERN table at the end of the .aff file has fewer lines than its count

Finding LFV-345Area: analysis / hunspell (Dictionary affix-file parsing)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 load a hunspell dictionary whose .aff file ends with a REP, MAP, ICONV/OCONV, COMPOUNDRULE, BREAK or CHECKCOMPOUNDPATTERN table that announces more lines than it holds (for example 'REP 2' followed by a single REP line, as a cut-off download or a careless hand edit leaves it), and expect the parse error that the Dictionary constructors document (ParseException), which is what Lucene already throws for a PFX/SFX table cut short ('Premature end of rules') and, since 10.2.0, what the tolerateRepRuleCountMismatches() javadoc promises for a wrong REP count by default. Instead the parser passes the null that readLine() returns at end of file straight into a string method and throws NullPointerException ('Cannot invoke "String.split(String)" because "line" is null'), with no directive or line number, which also bypasses HunspellStemFilterFactory's 'Unable to load hunspell data!' wrapping of ParseException. The file is refused either way; only the error is wrong.

The test shows that hunspell Dictionary built from an .aff file that ends in REP 2 followed by only one REP a b line fails with a NullPointerException.

Expected vs actual

Expected: ParseException (tolerateRepRuleCountMismatches() is false by default: "a ParseException will happen"). Actual: NullPointerException: Cannot invoke "String.split(String)" because "line" is null.

Files

src/org/apache/lucene/analysis/hunspell/TestTruncatedRepTable.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/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.TestTruncatedRepTable

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.