matchhighlight PassageFormatter closes crossing markers in opening order instead of innermost first, so per-marker end strings come out mis-nested (e.g. '<a>one <b>two</a></b><b> three</b>' instead of '<a>one <b>two</b></a><b> three</b>')

Finding LFV-609Area: highlighter / matchhighlight: PassageFormatter multi-marker formatting (crossing markers with per-marker end strings; also end to end through MatchHighlighter, FieldValueHighlighters.highlighted and MatchHighlighter.QueryOffsetRange)Priority: lowImpact: minorNovelty: new

Finding page for LFV-609

AI-assisted finding, confirmed by automated checks, not yet triaged by a human Lucene committer. This site files nothing upstream.

What it shows

You format the passage 'one two three' with two crossing markers, [0,7) written as <a>...</a> and [4,13) as <b>...</b>, using PassageFormatter's Function constructor, or you highlight the crossing phrase queries 'one two' and 'two three' with MatchHighlighter.highlight(topDocs, q1, q2) and one tag per query. You expect well-nested output, '<a>one <b>two</b></a><b> three</b>', because when a marker ends the formatter closes and re-opens the markers opened after it precisely to resolve the overlap into nested markup (Passage javadoc: markers 'can be overlapping or nested'). Instead it closes those markers in opening order rather than innermost first and returns '<a>one <b>two</a></b><b> three</b>' (end to end '<q1>one <q2>two</q1></q2><q2> three</q2>'), which an XML parser rejects.

The test shows that matchhighlight PassageFormatter, with per-marker end strings, closes two crossing markers in opening order instead of innermost first, so the end tags come out mis-nested.

Expected vs actual

For 'foo bar baz' with [0,7) as <a> and [4,11) as <b>: expected <a>foo <b>bar</b></a><b> baz</b>; actual <a>foo <b>bar</a></b><b> baz</b>, with -ea and -da.

Files

Run it

# 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/highlighter/build/libs/lucene-highlighter-$V.jar
CP=$CP:$LUCENE/lucene/memory/build/libs/lucene-memory-$V.jar
CP=$CP:$LUCENE/lucene/queries/build/libs/lucene-queries-$V.jar
CP=$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.search.matchhighlight.TestPassageFormatterCrossingMarkers

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.