IGNITE-28831 Fix DTO serializer codegen NPE on type-use annotated qualified types

[anton-vinogradov]

Description

IGNITE-28831

IgniteDataTransferObjectProcessor throws a NullPointerException during annotation processing, which breaks compilation of modules/core from source:

mvn -o -q -pl modules/core -am test-compile -DskipTests -Dcheckstyle.skip=true

Root cause

IDTOSerializerGenerator.className(TypeMirror) stripped everything before the first space to drop a leading type-use annotation (e.g. @NotNull java.util.Collection). But the compiler renders a type-use annotation (@Nullable/@NotNull) inline, right before the simple name of a qualified type:

java.util.@org.jetbrains.annotations.NotNull Collection<...>

The first-space heuristic discarded the java.util. qualifier and returned only Collection, which caused:

1. COLL_IMPL.get("Collection") → null → NPE in simpleName() for fields such as BaselineNode.addrs (@NotNull Collection<ResolvedAddresses>) and IdleVerifyResult.txHashConflicts (@Nullable List<List<TransactionsHashRecord>>).
2. Malformed import String; / import Exception; / import IdleVerifyResult; in the generated serializers for DurableBackgroundCleanupIndexTreeTaskV2, SnapshotPartitionsVerifyResult, VisorTaskResult (the '.' expected compile errors) for @Nullable-annotated fields.

The subsequent cascade of cannot find symbol: class *ViewWalker errors is a side effect: the processor's exception aborts the annotation-processing round, so the separate SystemViewRowAttributeWalkerProcessor output never gets compiled.

Fix

Strip type-use annotations wherever they occur (preserving the package qualifier) instead of the first-space heuristic. The change is confined to the codegen module; DTO classes are not touched.

Verification

mvn -o -q -pl modules/core -am test-compile -DskipTests -Dcheckstyle.skip=true completes with BUILD SUCCESS, and the serializers for BaselineNode, IdleVerifyResult, DurableBackgroundCleanupIndexTreeTaskV2, SnapshotPartitionsVerifyResult, VisorTaskResult are generated and compile.

🤖 Generated with Claude Code

[github-actions]

Possible compatibility issues. Please, check rolling upgrade cases

This PR modifies protected classes (with Order annotation).
Changes to these classes can break rolling upgrade compatibility.

Affected files:

• modules/codegen/src/main/java/org/apache/ignite/internal/idto/IDTOSerializerGenerator.java