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[CALCITE-7736] Replace the Checker Framework with NullAway and JSpecify - #5213

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@vlsi vlsi commented Aug 23, 2026

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Preview, not ready to merge. NullAway still reports 576 errors in calcite-core and 126 in calcite-linq4j, so the nullness CI job is red on purpose. The point is to show the migration and the shape of what remains. See CALCITE-7736.

Why

The Checker Framework needs a Gradle plugin of its own, 48 .astub files that patch the nullness of the JDK and of third-party libraries, and two dedicated CI jobs. NullAway is a single Error Prone check: no separate plugin, no stub files, and nullness models for the JDK and for popular libraries out of the box. The annotations come from JSpecify, a specification that several checkers read, rather than from one checker's own package.

What

Six commits, each doing one thing:

Commit
Replace the Checker Framework with NullAway and JSpecify build and CI only
Move @Nullable and @NonNull from the Checker Framework to JSpecify mechanical rename; 1197 insertions against 1197 deletions, and no changed line touches anything but those two imports
Declare @NullMarked on the packages that NullAway verifies plus LintTest.testLintNullMarked
Migrate the Checker Framework annotations that JSpecify does not define @PolyNull, @MonotonicNonNull, @Pure, the initialization annotations, and the rest
Replace @PolyNull with @Contract 108 clauses
Give type parameters the nullable bounds the Checker Framework inferred 61 declarations

The rename commit is worth skimming rather than reading. Commits 1 to 3 do not build on their own, because the source still carries Checker Framework annotations after checker-qual is gone; from commit 4 onward every commit compiles.

NullAway is configured in JSpecify mode with the experimental generics support (JSpecifyExperimental, HandleWildcardGenerics, JSpecifyJDKModels, WarnOnGenericInferenceFailure) and with CheckContracts. It is an error in the projects listed in nullawayProjects and off elsewhere, so a nullness problem fails one CI job rather than every test job.

org.apache.calcite.linq4j.annotations is new and holds @Contract, @MonotonicNonNull, @RequiresNonNull, @EnsuresNonNull and @EnsuresNonNullIf. NullAway matches these by the last component of their name rather than by their package, so Calcite declares its own and takes no dependency on the checker.

The part worth reviewing

The two tools default an unwritten type parameter bound in opposite directions. CLIMB-to-top gives implicit bounds the top qualifier, so <T> under the Checker Framework means <T extends @Nullable Object>; JSpecify fills in Object, which under @NullMarked is non-null. Every unbounded type parameter therefore changed meaning, and Calcite relied on the Checker Framework reading — SqlShuttle extends SqlBasicVisitor<@Nullable SqlNode> was passed to SqlNode.accept(SqlVisitor<R>) with no suppression, which typechecks only if R admits a nullable argument.

Writing the bound out at 61 declarations took NullAway from 1126 errors to 576. Pair.of alone was worth 132: its class already had the bounds, but a static factory declares type parameters of its own.

The erasure is unchanged, so these are binary compatible.

How to verify

./gradlew -PenableErrorprone :linq4j:classes :core:classes

Needs JDK 21, which Error Prone 2.43 and later require.

classes, testClasses, checkstyleMain, checkstyleTest and autostyleCheck pass. :core:test and :linq4j:test run 18866 tests with no failures.

Open questions

  • nullawayProjects lists :linq4j and :core. The Checker Framework jobs also covered :server.
  • Should the annotations live in a separate calcite-annotations module rather than in calcite-linq4j?
  • NullAway crashes with an IndexOutOfBoundsException when a @Contract clause names more arguments than the call site passes: ContractHandler.onDataflowVisitMethodInvocation reads arguments by the antecedent's length, and validates the arity on declarations but not at call sites. Worth reporting upstream. Avoided here by not annotating receiver parameters or varargs methods.

*/
public void request(QueryType queryType, String data, Sink sink,
List<String> fieldNames, List<ColumnMetaData.Rep> fieldTypes,
List<String> fieldNames, List<ColumnMetaData.@Nullable Rep> fieldTypes,

@vlsi vlsi Aug 25, 2026

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This might better be List<? extends ColumnMetaData.@Nullable Rep>, however, AFAIK it would change public API signature, so it would not be 100% backward compatible

@sonarqubecloud

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@@ -403,6 +411,11 @@
actualMessage = Util.toLinux(actualMessage);
}

if (expectedMsgPattern == null) {
actualException.printStackTrace();
mihaibudiu and others added 13 commits August 26, 2026 13:51
…erator

Signed-off-by: Mihai Budiu <mbudiu@feldera.com>
…the compiler

Signed-off-by: Mihai Budiu <mbudiu@feldera.com>
…ted LATERAL sub-queries with window functions
…Y clause in window function within correlated subquery
…nested ROW values

Signed-off-by: Mihai Budiu <mbudiu@feldera.com>
…th ROW_NUMBER window function due to RexOver nullability mismatch
…cket behind

Signed-off-by: Mihai Budiu <mbudiu@feldera.com>
vlsi and others added 29 commits August 26, 2026 13:53
…alues

A profiled row carries a value per column, and a column may have none, so
`Collector.add` and its three overrides take `List<@nullable Comparable>` and
`CompositeCollector` keeps a `@Nullable Comparable[]`.

`FlatLists.of(T, T, T)`, the six statics of `CompositeList` and
`SqlBasicCall.set` take the nullable element bound of the lists they build.
`LatticeSuggester` keys a node by its parent, and a root has none;
`AggregateReduceFunctionsRule` names the extra columns it projects, of which the
new ones have no name yet.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
…ived its reason

`SqlToRelConverter` reads the project it has just cast rather than casting it at
each use, and asks for a `DmlNamespace` after `isWrapperFor` has established
there is one. `SqlValidatorImpl` collects aliases into a list that admits the
null a child of the FROM clause may have, and looks up a column by an index it
took from the map it is reading.

`JavaRowFormat.copy` returns a list of statements and never null, so the
`castNonNull` around it in `EnumUtils` goes away.

`FilterProjectTransposeRule` answers `replaceIfs` with null when the input has
no distribution, rather than a singleton list holding null. `replaceIfs` takes a
supplier that may answer null, and does the same thing with it.

`CalciteCatalogReader` falls back on a family constant, which is what
`firstNonNull` is for.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
`ProfilerImpl` separates the two kinds of row it works with: a scanned row uses
`NullSentinel` for a SQL null and so holds no Java null, while the sketch path
builds a sparse row filled only at the ordinals of the space it feeds.
`Collector.add` takes `List<? extends @nullable Comparable>` so it accepts
both, and each collector casts the ordinals its own space owns.

Type parameters that carry the nullable bound of what they build:
`RexWindowBound.accept` and its override, `Functions.ignore2`, `Util.combine`,
`SqlNodeList.toArray`, `HepPlanner.onCopyHook`, `EnumerableTableModify.keyOf`
and the maps keyed by it, and `ArrayTable.asList`.

`SqlNode.toList` and `RelBuilder` replace a method reference and a Guava call
whose wildcard comes from bytecode with a lambda and a direct iterator check.
`TableFunctionScanNode` drops its raw `Enumerable` for a typed one.

`ArrayTable.permute` is suppressed: an array creation keeps a non-null component
type whatever it is assigned to, so writing a nullable element reports even
though both arrays are declared `@Nullable Comparable[]`.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
…nterface declares

A visitor over SqlNode declares itself SqlBasicVisitor<@nullable Void> or
SqlVisitor<@nullable Void>, so its visit methods return @nullable Void. The
overrides narrowed that to Void, which for a type whose only value is null
promises nothing, and NullAway could not infer R for SqlNode.accept: the
argument constrained it to be both @nonnull and @nullable.

See uber/NullAway#1733

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
NullAway 0.12.13 and later ship a RequireExplicitNullMarking Error Prone check
that fails a top-level class which is neither annotated nor covered by an
annotated package or module. It is what the OnlyNullMarked setting needs, and
it is stricter than the LintTest check it replaces: a class that sits in a
package with no package-info.java is reported by name, whether or not the
package holds a package-info.java at all.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
The Checker Framework covered :server as well, so NullAway takes it over. The
module needs no source changes: its four main classes live in
org.apache.calcite.server, a package that :core already declares @NullMarked,
and the generated DDL parser sits under a javacc directory, which the
XepExcludedPaths setting skips the way AskipDefs used to.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
The Druid adapter now declares its package @NullMarked, and NullAway verifies
it. Most of the change is stating in the signatures what the bodies already
did: a visitor over a Druid column returns a pair whose halves are both absent
when the column cannot be pushed down, an extraction function carries no
granularity and no locale, and the filters and plans that writeFieldIf skips
take an absent value.

Three places said something the code did not mean. Only the Checker Framework
needed the preconditions on DruidTable.create and DruidType.getTypeFromMetric,
whose callers are now the ones that check. DruidProjectRule named a field null
for an expression that is not an input reference, but splitProjects puts
nothing but input references there, so the branch was dead. And a rolled-up
column with no parent node dereferenced that parent, where the Table contract
has said it may be absent since the method was introduced.

The Jackson result classes keep non-null fields under a NullAway.Init
suppression, since Druid always populates them; the three that depend on the
analysis types the query asked for are @nullable, which is what the reader of
aggregators already assumed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
The file adapter now declares its package @NullMarked, and NullAway verifies
it. A CSV cell, a table name in a model, and a field configuration are all
absent-able, and the signatures now say so: field() reads a row whose cells may
be absent, the row converters carry a nullable element type, and FileSchema
falls back to the source path through Util.firstNonNull rather than through the
@contract on Util.first, which NullAway cannot read.

Two lazily populated fields were the reason for the remaining reports.
FileReader.getTable wrote its result into tableElement and returned nothing, so
no caller could see that the field was populated; it is now readTable, which
returns the element it read. The bad-source-column check in FileRowConverter
looked the heading up twice, once to validate and once to take the index, and
now does both at once.

A model that names no file for a CSV table, or no url for an HTML table, was
already a NullPointerException deeper in; requireNonNull names the missing
operand instead.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
The model that the adapter's own test uses names neither bootstrap.servers nor
topic.name, because a table that injects its own consumer needs neither, so
both options are optional and KafkaTableOptions now says so. That reaches
KafkaRowConverter.rowDataType, whose topic name is absent for such a table;
neither implementation looks at it. The bootstrap servers are required on the
path that builds a consumer, and requireNonNull there names the missing operand
rather than letting the Kafka client report it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
SparkValues read the rowType field, which AbstractRelNode keeps as a lazily
computed cache, where it meant the row type its constructor was given;
getRowType() is the accessor that always has one. EnumerableToSparkConverter
throws before it reaches its unfinished body, so the body is gone and the
comment that describes what it would generate stays.

RexToLixTranslator.translateCondition passes its correlates argument straight
to setCorrelates, which has always accepted null, so the parameter says so now.
That is what lets SparkCalc convert a program that has no correlates.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
The call factory for Babel's CREATE TABLE takes the collection type out of a
symbol literal, and SqlLiteral.symbolValue returns null for a literal that
holds no symbol. The parser always writes one, so requireNonNull states that
rather than leaving the constructor to find out.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
A Redis schema with no password is the ordinary case, and it reaches the pool
config through RedisConfig and RedisJedisManager, both of which say so now.
RedisSchema validated its operands through isEmptyObject, whose result NullAway
cannot connect back to the value, so the checks name the value they read and
read it once. RedisTable had a RedisEnumerator field that nothing ever read.

The anonymous Enumerable in RedisTable.scan is now a named inner class. NullAway
checks an anonymous class's overrides against the erased supertype, dropping the
@nullable on its type argument, so it reported the enumerator() override as a
nullability mismatch; a named subclass with the same type argument is accepted.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
The push-down rule builds a search string from whichever of the two projections
and the two row types the match happened to have, so those parameters are
optional and the signature says so. A literal that is neither numeric nor CHAR
yields no search text, which is how getFilter already reads the result.

SplunkResultEnumerator reads the CSV header in its constructor, and a header it
could not read leaves the field names absent; moveNext now stops instead of
dereferencing them. close() swallowed the NullPointerException it raised on a
null Closeable, and returns early instead.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
A MongoDB document has no value for a field it does not carry, so a projection
of one field enumerates nulls, and the getter, the enumerator and the enumerable
that carry it now say so. That needed the element type of AbstractEnumerable to
admit null, which Enumerable and Queryable have admitted all along; the four
interfaces between them said otherwise, and now agree.

The filter translator builds its documents with JsonBuilder, whose maps and
lists hold absent values, and it passes a null operator to mean equality, which
translateOp2 has always read that way.

The two anonymous Enumerables in MongoTable are named classes, to avoid
uber/NullAway#1746.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
A Cassandra row has no value for a column it never set, so the enumerator and
the enumerable that carries it enumerate nulls. The tuple components a STRUCT
holds are already collected through requireNonNull, which is where the comment
saying null cannot appear inside a collection lives.

The enumerable is a named class rather than an anonymous one, to avoid
uber/NullAway#1746.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
The Pig rel nodes look down the tree for the table they act on, and a tree with
no table underneath returns none, which is what RelNode.getTable has always
said. PigToEnumerableConverter read the rowType field, AbstractRelNode's lazily
computed cache, where it meant this node's row type.

A model that names no file or no columns for a Pig table reached the File and
the array with a null; requireNonNull names the missing operand.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
An Arrow vector holds a null wherever the column has no value, which getValue
returns for a timestamp and the enumerator hands on, so the enumerator, the
enumerable and the query that builds it carry a nullable element type. The
precondition on query's field list is one the ImmutableIntList parameter
already makes.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
An InnoDB row has no value for a column that holds none, which the enumerator
returns and the row array carries. The implementor and the internal expression
node are filled in as the translation proceeds, so their fields are marked
NullAway.Init rather than pretending a half-built object never exists. A model
that names no sql file or no data file path reached the schema with a null;
requireNonNull names the missing operand.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Piglet keeps four maps from a relation to its alias and its Pig operator, and
looking a name up in them can miss, which the getters now say. Handler looked
its relations up the same way and pushed whatever came back, including nothing;
it now reports the unknown name instead of failing later in the builder.

PigTable.scan returned null rather than an enumerable, and nothing could have
used it; it throws. SqlUserDefinedFunction declared its operand type inference
non-null though SqlFunction below it has always accepted none, which is what
PigUserDefinedFunction passes.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
…left behind

The query enumerable still had the non-null element type, and its anonymous
form ran into uber/NullAway#1746 once the type argument admitted null. It is a
named class now, like the ones in :redis, :mongodb and :cassandra.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
…e class allows

Aggregate.copy is handed no grouping sets when the aggregate has a single
group, and PigAggregate.copy passes that straight to its own constructor,
which declared them required.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
…autostyle wants

Lint:skip

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
A Geode entry has no value for a field it does not carry, which the converters
return and the enumerator hands on. The two schema factories read four operands
out of the model and passed them on unchecked; requireNonNull names whichever
one is missing. The lazily built table maps and the limit an implement context
may not have say so.

Region's value type is a bytecode wildcard whose upper bound reads as nullable,
so the value constraint cannot be held in a Class<?>; a raw Class avoids it.
See uber/NullAway#1732.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
An Elasticsearch hit carries either _source or fields and never both, so each
of the two is absent half the time, and a document has no value for a field it
does not carry. That runs through the getters, the row converters and the
aggregation buckets, whose key is absent for a missing bucket.

The predicate analyzer reads a literal that may hold no value: a range bound
needs one and says so, while a term query writes whatever it got. A LIKE with
no escape, a projection that is not an item reference, and an expression the
analyzer cannot convert are all absent results the callers already handled.

The schema factory takes the credentials and the path prefix from the model,
where they are optional.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
An os table function returns a row whose columns are absent wherever the
command printed nothing, which the enumerators and the line parsers now carry.
Ten of them built the same anonymous enumerable over an osquery table; they
share OsQueryEnumerable instead, which also avoids uber/NullAway#1746, as do
the named enumerator in the stdin function and the named line parser in vmstat.

os.name is absent on a JVM that does not publish it, and the table functions
switch on it. SqlShell prints a column that has no value, and looks a column
label up in a map that may not hold it. The Avatica server for Chinook holds
its server and its meta instance from the point it starts them.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
…verification

A model that names no directory for a CSV schema, and no file for a CSV table,
reached the File with a null; requireNonNull names the missing operand. The
filterable table pushed down a literal that may hold no value. The maze
enumerates without a solution set when the table is asked for the maze alone,
which is what the null argument means.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
The test fixtures carry absent values everywhere a SQL value can be null: the
expected result of checkScalar and checkString, the column a result set reads,
the origins and unique keys the metadata query may not know, and the alias a
Pig relation may not have. The mock catalog and the mock planner fill their
fields in as registration proceeds, so those are marked NullAway.Init.

Twelve classes took the @nullable argument that Object.equals has always
allowed. DiffRepository reads a DOM, where a node list yields no node past its
length and an attribute may carry no value; the reads that cannot miss say so
by name. The eight schemata packages that had no package-info.java now have
one.

BaseQueryable in :linq4j required a provider, though Smalls builds one that
overrides enumerator() and never asks a provider to execute it; getProvider
still refuses to return null. Four anonymous enumerables became named classes,
to avoid uber/NullAway#1746.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
The benchmarks keep their sources in the jmh source set rather than a main one,
so the verification follows them there, and the errorprone CI job builds
jmhClasses alongside classes. A JMH state class is filled in by the @setup
methods and the @PARAM values, which is what NullAway.Init says; the rest is the
usual: a statistics map that a phase may not have produced, an employee with no
commission, and an edge the graph may not hold.

Two Error Prone warnings that the jmh source set had never been built against
are fixed rather than suppressed: a helper that reads no instance state is
static, and a parse failure during setup is thrown rather than printed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Co-Authored-By: Codex GPT 5.6-Terra <codex@openai.com>
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