Undefined CLONES array dereference aborts DBIx::Abstract test on both backends

Start by reproducing the failure with the upstream t/2-dbix-abstract.t from DBIx-Abstract-1.04, which fails at line 55 on the is( @{$dbh->{'CLONES'}}, 0, ...) assertion. The issue says the standalone expression does not reproduce it, so reduce the disconnect, reconnect and explicit DESTROY sequence before looking into the runtime. Done means the minimized case passes on both JVM and interpreter backends, and t/2-dbix-abstract.t completes all 27 tests.

Summary

DBIx-Abstract-1.04 passes its complete upstream test suite under system Perl but aborts under PerlOnJava on both execution backends. The failure occurs at the CLONES count assertion after a DBIx::Abstract object has been disconnected, reconnected, and another wrapper around its DBI handle has been explicitly destroyed.

Reproduction

Run the upstream t/2-dbix-abstract.t test from distribution DBIx-Abstract-1.04 with Check::ISA-0.09, DBI, and DBD::SQLite available. After the first nine assertions pass, PerlOnJava reports:

Can't use an undefined value as an ARRAY reference at t/2-dbix-abstract.t line 55.

The failing assertion is:

is( @{$dbh->{'CLONES'}}, 0, "no clones yet");

Immediately before it, the test has disconnected and reconnected $dbh, created a second DBIx::Abstract object around $dbh->{'dbh'}, explicitly called $dbh2->DESTROY(), then verified that $dbh is still connected. The CLONES key is absent at this point. System Perl evaluates the array dereference in the is argument list as an empty list and the assertion passes; PerlOnJava aborts while evaluating that expression.

Evidence

• CPAN tester run 20261013-145839-84917, distribution DBIx-Abstract-1.04.
• System Perl 5.42.2: full upstream suite passes, 27/27 tests. Check::ISA-0.09 also passes its available tests; its optional asa test is skipped because asa is not installed.
• PerlOnJava 5.44.1, Java 24.0.2, macOS arm64: the archived JVM run fails at test 10. Re-running the focused upstream file with the archived executable reproduces the same failure on both JVM and interpreter backends.
• DBI and DBD::SQLite load successfully in PerlOnJava, and the first nine DBIx::Abstract assertions pass, ruling out missing DBI/SQLite prerequisites as the cause.
• The standalone expression on a fresh hash does not reproduce the failure. The trigger requires the test's DBIx::Abstract connection/reconnect and explicit-destruction sequence.
• GitHub duplicate search found no issue for the CLONES failure or this array-dereference behavior. Issue #1419 concerns Valiemon test failures and is unrelated.

Root cause

The confirmed compatibility failure is in PerlOnJava's evaluation of the array dereference in this list-valued Test::More::is argument after the DBIx::Abstract lifecycle sequence. The missing CLONES field should contribute zero list elements, as it does under system Perl; instead, PerlOnJava treats it as an invalid array reference and throws before the assertion can run. The failure is shared by both execution backends, so the defect is in shared runtime semantics rather than backend-specific execution or DBIx::Abstract itself.

The minimal trigger has not yet been reduced below the upstream lifecycle sequence. Investigation should trace how the undefined CLONES hash value and its context are represented after the explicit DESTROY call, then identify why the array dereference is rejected here while ordinary cases pass.

Proposed fix

Correct the shared runtime's handling of an undefined hash-element value dereferenced as an array in list context so that it follows Perl's behavior and yields an empty list in this case. Preserve an integration regression covering the DBIx::Abstract disconnect/reconnect and explicit-DESTROY sequence, and add a smaller unit regression once the trigger is isolated. Validate the new unit test with system Perl first, then require the focused regression and upstream test to pass on both PerlOnJava backends.

Acceptance criteria

• A minimized test that passes with system Perl also passes on JVM and interpreter backends.
• t/2-dbix-abstract.t completes all 27 tests on both PerlOnJava backends.
• The standard-Perl oracle remains green for any new project-owned unit regression.