SoraniNormalizer tests for format characters one UTF-16 char at a time, so format characters outside the BMP (U+E0001, the tag characters U+E0020..U+E007F, U+1BCA0..U+1BCA3, U+1D173..U+1D17A and others) are kept in the term, while BMP ones such as RLM and LRM are removed

Finding LFV-752Area: analysis-common / Sorani normalizer (SoraniNormalizer.normalize; SoraniNormalizationFilter, SoraniAnalyzer and the 'soraniNormalization' factory)Priority: lowImpact: silent wrong resultsNovelty: new

Finding page for LFV-752

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 Sorani Kurdish text with the stock SoraniAnalyzer or SoraniNormalizationFilter. The normalizer's javadoc says formatting characters are removed, and it does remove BMP ones such as the right-to-left mark, so کورد + X + ستان should become کوردستان for any invisible format character X. Instead it calls Character.getType on one UTF-16 char at a time, so a format character outside the BMP (for example U+E0001 or a tag character), which Java stores as two surrogate chars, is never recognized: it stays in the term, and the word no longer matches the same word without it, with no error.

The test shows that SoraniNormalizationFilter removes BMP format characters such as U+200F, but it keeps the format character U+E0001, which is outside the BMP, because SoraniNormalizer tests Character.getType on one UTF-16 char at a time.

Expected vs actual

Expected: \u06A9\u0648\u0631\u062F + U+E0001 + \u0633\u062A\u0627\u0646 becomes \u06A9\u0648\u0631\u062F\u0633\u062A\u0627\u0646. Actual (-ea and -da): U+E0001 stays in the term (the ComparisonFailure shows it as an invisible character inside []).

Files

src/org/apache/lucene/analysis/ckb/TestSoraniNormalizationFilterSupplementaryFormatChar.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.ckb.TestSoraniNormalizationFilterSupplementaryFormatChar

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.