StandardQueryParser with setMultiFields normalizes field-less prefix and wildcard terms with field null, before the multi-field expansion, so per-field analyzers are ignored for them (and a PerFieldAnalyzerWrapper over Map.of throws NullPointerException)

Finding LFV-560Area: queryparser / flexible StandardQueryParser (processor pipeline order: WildcardQueryNodeProcessor runs before MultiFieldQueryNodeProcessor)Priority: lowImpact: silent wrong resultsNovelty: new

Finding page for LFV-560

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

What it shows

You give StandardQueryParser a PerFieldAnalyzerWrapper (WhitespaceAnalyzer by default, StandardAnalyzer for 'title'), call setMultiFields({title}) and parse 'Luc*' with no field, expecting what the javadoc promises: the clause expanded over the multi fields, i.e. the same query as 'title:Luc*', which becomes title:luc* and finds the document titled 'Lucene'. Instead the pipeline normalizes the prefix in WildcardQueryNodeProcessor before MultiFieldQueryNodeProcessor has set the field, so Analyzer#normalize is called with field null (the wrapper's default analyzer), the query becomes title:Luc* and finds nothing, while plain, fuzzy, regexp and range clauses in the same setup are normalized with the expanded field. If the per-field map is a Map.of, the null lookup makes parse() throw NullPointerException for every field-less prefix or wildcard clause.

The test shows that StandardQueryParser with setMultiFields({title}) normalizes the field-less prefix Luc* with field null (the wrapper's default analyzer) instead of the analyzer of title, the field it expands to.

Expected vs actual

Expected: parse("Luc*", null) equals parse("title:Luc*", null), i.e. title:luc*. Actual: expected:<title:luc*> but was:<title:Luc*> (-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/analysis/common/build/libs/lucene-analysis-common-$V.jar
CP=$CP:$LUCENE/lucene/facet/build/libs/lucene-facet-$V.jar
CP=$CP:$LUCENE/lucene/queries/build/libs/lucene-queries-$V.jar
CP=$CP:$LUCENE/lucene/queryparser/build/libs/lucene-queryparser-$V.jar
CP=$CP:$LUCENE/lucene/sandbox/build/libs/lucene-sandbox-$V.jar
CP=$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.queryparser.flexible.standard.TestMultiFieldWildcardNormalize

The module(s) facet also need their third-party runtime jars; ./gradlew -p lucene/<module> dependencies lists them.

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.