Add Suppliers2 and Iterators2 to io.spine.util

[alexander-yevsyukov]

Suppliers2 and Iterators2 were introduced in SpineEventEngine/core-jvm#1656 as @Internal wrappers over Guava's Suppliers.memoize and Iterators.filter. Guava declares those methods as <T extends @Nullable Object> — deliberately, so that null values can flow — but under JSpecify semantics that bound stops T's nullness from being inferred from the assignment, so assigning the result to a non-null type in @NullMarked code reads as a nullness mismatch. Declaring plain <T> in a @NullMarked package binds T to non-null types and settles it.

What changed

• The two classes now live in io.spine.util (module base) — joining the established Guava-companion family there (Preconditions2, Predicates2). Hosting them at the bottom of the dependency graph shares them SDK-wide and lets core-jvm drop its copies.
• New Kotlin specs cover both:
  • Suppliers2Spec — the delegate's value is returned; evaluation is lazy and happens exactly once.
  • Iterators2Spec — order-preserving filtering; exhausted iterator when nothing matches; the returned view rejects remove().
  • Both extend UtilityClassTest, inheriting the final-class, private-constructor, and static-method null-hostility checks.
• The config submodule is updated, and the ErrorProne warnings and the PMD error surfaced by the refreshed toolchain are addressed across pre-existing base and environment sources (Identifier, MessageIdToString, FsObject, ComparisonOperator, ApiOption, TestsProperty, TypeSet, AnyPacker).
• Javadoc of the new classes is polished per the documentation review: @return tags added to both methods, and the Suppliers.memoize() link is labeled like the Iterators.filter() one.
• Version: 2.0.0-SNAPSHOT.424 → 2.0.0-SNAPSHOT.425; dependency reports regenerated.

Notes for the reviewer

• In the regenerated docs/dependencies/pom.xml, the error_prone_annotations entry moved 2.42.0 → 2.47.0. This is deterministic generator output — it reflects Guava 33.6.0's requested version, while the classpath resolution still forces 2.42.0 (verified with dependencyInsight); equal values already appear in master's dependencies.md. No dependency pin changed in this PR.
• Verification at PR-creation HEAD: ./gradlew build dokkaGenerate — green; spine-code-review, kotlin-engineer, and review-docs passes all approved.
• Follow-up (out of scope here): once this is published, core-jvm can replace its io.spine.server.Suppliers2/Iterators2 with imports from io.spine.util.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR adds Suppliers2 and Iterators2 utility wrappers to io.spine.util (module base) to avoid JSpecify nullness inference issues caused by Guava’s <T extends @Nullable Object> signatures in @NullMarked code, and introduces Kotlin specs to cover the new utilities. It also bumps the snapshot version and regenerates dependency reports accordingly.

Changes:

• Added io.spine.util.Suppliers2 / io.spine.util.Iterators2 as @Internal Guava-companion utilities.
• Added Kotlin specs (Suppliers2Spec, Iterators2Spec) extending UtilityClassTest.
• Bumped versionToPublish to 2.0.0-SNAPSHOT.425 and regenerated dependency report artifacts.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
version.gradle.kts	Bumps published snapshot version.
docs/dependencies/pom.xml	Regenerated dependency POM reflecting new snapshot + requested dependency versions.
docs/dependencies/dependencies.md	Regenerated dependency/license report with updated version and timestamp.
base/src/main/java/io/spine/util/Suppliers2.java	Introduces memoizing supplier wrapper (has a type mismatch bug to fix).
base/src/main/java/io/spine/util/Iterators2.java	Introduces filtering iterator wrapper (minor signature formatting inconsistency).
base/src/test/kotlin/io/spine/util/Suppliers2Spec.kt	Adds tests for lazy, single-evaluation memoization behavior.
base/src/test/kotlin/io/spine/util/Iterators2Spec.kt	Adds tests for order-preserving filtering and unsupported removal.
.agents/tasks/add-suppliers2-iterators2.md	Agent task tracking file (not reviewed; .agents/** is config-managed in this repo).

[Copilot]

Pull request overview

Copilot reviewed 20 out of 20 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 20 out of 20 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 20 out of 20 changed files in this pull request and generated no new comments.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.02%. Comparing base (3c8533f) to head (a517ec2).
⚠️ Report is 11 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #953      +/-   ##
==========================================
- Coverage   94.02%   94.02%   -0.01%     
==========================================
  Files         192      194       +2     
  Lines        4187     4182       -5     
  Branches      345      345              
==========================================
- Hits         3937     3932       -5     
  Misses        149      149              
  Partials      101      101              

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