#1338·auto

Nullable field nondeterministically has null check inserted anyhow

Author: kennknowlesCreated Jun 16, 2022Updated May 21, 2025

Labelstype=defectComponent: valueP3

Summary of issue: A field that is nullable is nondeterministically having a null check in the generated code, depending on what other build tasks occurred.

See https://lists.apache.org/thread/cdw4y50r3hl37z8y7x470m2mddclkqgv (from here you can gather more info from the thread)

Inline, paraphrasing the thread...

To reproduce:

bash

git clone https://github.com/apache/beam
cd beam
git checkout 4ffeae4d2b800f2df36d2ea2eab549f2204d5691~1
./gradlew :runners:direct-java:compileJava
less
./runners/direct-java/build/generated/sources/annotationProcessor/java/main/org/apache/beam/runners/direct/AutoValue_ImmutableListBundleFactory_CommittedImmutableListBundle.java

git checkout 4ffeae4d2b800f2df36d2ea2eab549f2204d5691
./gradlew :runners:direct-java:compileJava
less
./runners/direct-java/build/generated/sources/annotationProcessor/java/main/org/apache/beam/runners/direct/AutoValue_ImmutableListBundleFactory_CommittedImmutableListBundle.java

./gradlew :runners:direct-java:compileJava --rerun-tasks
less
./runners/direct-java/build/generated/sources/annotationProcessor/java/main/org/apache/beam/runners/direct/AutoValue_ImmutableListBundleFactory_CommittedImmutableListBundle.java

The class at https://github.com/apache/beam/blob/1dff59b4ff26310f88f927edfcf44709ed6ea9c2/runners/direct-java/src/main/java/org/apache/beam/runners/direct/ImmutableListBundleFactory.java#L130

java

abstract static class CommittedImmutableListBundle<T> implements CommittedBundle<T> {
    public static <T> CommittedImmutableListBundle<T> create(
        @Nullable PCollection<T> pcollection,
        StructuralKey<?> key,
        Iterable<WindowedValue<T>> committedElements,
        Instant minElementTimestamp,
        Instant synchronizedCompletionTime) {
      return new AutoValue_ImmutableListBundleFactory_CommittedImmutableListBundle<>(
          pcollection, key, committedElements, minElementTimestamp, synchronizedCompletionTime);
    }
  ...
}

extends https://github.com/apache/beam/blob/1dff59b4ff26310f88f927edfcf44709ed6ea9c2/runners/direct-java/src/main/java/org/apache/beam/runners/direct/CommittedBundle.java#L35

java

interface CommittedBundle<T> extends Bundle<T, PCollection<T>> {
  /** Returns the PCollection that the elements of this bundle belong to. */
  @Override
  @Nullable
  PCollection<T> getPCollection();

  ...
}

In all cases the PCollection field should be nullable.

In a "good" build, the AutoValue generated code constructor does not check for null

java

AutoValue_ImmutableListBundleFactory_CommittedImmutableListBundle(
    @Nullable PCollection<T> PCollection,
    StructuralKey<?> key,
    Iterable<WindowedValue<T>> elements,
    Instant minimumTimestamp,
    Instant synchronizedProcessingOutputWatermark) {
  this.PCollection = PCollection;

in a 'bad' build, the autovalue java is re-generated, but has an added nullness check:

java

AutoValue_ImmutableListBundleFactory_CommittedImmutableListBundle(
    PCollection<T> PCollection,
    StructuralKey<?> key,
    Iterable<WindowedValue<T>> elements,
    Instant minimumTimestamp,
    Instant synchronizedProcessingOutputWatermark) {
  if (PCollection == null) {
    throw new NullPointerException("Null PCollection");
  }
  this.PCollection = PCollection;

and then with --rerun-tasks it gets re-re-generated without the nullness check.

Source: google/auto

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