arne-bdt opened a new issue, #3941:
URL: https://github.com/apache/jena/issues/3941
### Version
6.2.0-SNAPSHOT
### What happened?
### Description
The spliterators in `org.apache.jena.mem.spliterator` —
`ArraySpliterator`, `ArraySubSpliterator`, `SparseArraySpliterator`,
and `SparseArraySubSpliterator` — report `Spliterator.IMMUTABLE` from
their `characteristics()` method. This is inconsistent with their
actual behavior: each one snapshots `set.size()` at construction time
and throws `ConcurrentModificationException` from `tryAdvance` /
`forEachRemaining` when the underlying collection is structurally
modified during traversal.
The Javadoc for `Spliterator.IMMUTABLE` states that an immutable
spliterator's element source "cannot be structurally modified".
Reporting `IMMUTABLE` while detecting and reporting structural
modification is a contract violation and can mislead stream pipelines
or downstream callers that inspect characteristics.
### Related issue: NONNULL not enforced
The same spliterators also report `NONNULL`, but the backing map and
set implementations (`FastHashMap`, `FastHashSet`, `HashCommonMap`,
`HashCommonSet`) accept `null` keys and values without complaint.
While none of the current internal callers pass `null`, the interface
contract was not documented and not enforced, so the `NONNULL`
characteristic was technically also unsubstantiated.
### Proposed fix
- Drop `IMMUTABLE` from `characteristics()` in the four spliterators.
- Document on `JenaMap`, `JenaMapIndexed`, `JenaSet`,
`JenaSetHashOptimized`, and `JenaSetIndexed` that null keys/values
are not permitted.
- Add `assert` checks on the write paths of the map/set
implementations to catch violations in tests.
### Scope
Internal to `jena-core` memory collections. No public API change; the
affected interfaces are package-internal helpers used by the in-memory
graph stores.
### Relevant output and stacktrace
```shell
```
### Are you interested in making a pull request?
None
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