feat: implement CHECK_IS_NULL handling for undef mock returns

[Koan-Bot]

What

Wire up the CHECK_IS_NULL constant so mock callbacks returning undef cause the OP to return undef to the caller.

Why

CHECK_IS_NULL was exported but never acted on (TODO at XS lines 71, 269). Callbacks returning undef were silently coerced to CHECK_IS_FALSE (0) — harmless for boolean ops, but wrong for numeric ops like -s where 0 means "file has zero size" and undef means "file not found". The _check_from_stat helper already returned CHECK_IS_NULL for missing stat fields (e.g. -M without mtime), but the value was swallowed.

How

• XS layer: _overload_ft_ops() now pops as SV and checks SvOK() to detect undef, returning -2 as a sentinel. All three PP handlers (pp_overload_ft_yes_no, pp_overload_ft_int, pp_overload_ft_nv) route -2/undef through FT_RETURNUNDEF.
• Perl layer: _check() propagates undef early (before the !$out → CHECK_IS_FALSE path). CHECK_IS_NULL added to @CHECK_STATUS exports.

Testing

• New t/check-null.t with 18 tests covering boolean ops (-e, -f, -d), integer op (-s), NV ops (-M, -A, -C), errno behavior, and FALLBACK_TO_REAL_OP coexistence.
• Full suite passes: 52 files, 1249 tests.

🤖 Generated with Claude Code

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Quality Report

Changes: 3 files changed, 240 insertions(+), 17 deletions(-)

Code scan: clean

Tests: passed (0 Tests)

Branch hygiene: clean

Generated by Kōan post-mission quality pipeline

[atoomic]

@Koan-Bot rebase

[Koan-Bot]

Rebase: feat: implement CHECK_IS_NULL handling for undef mock returns

Branch koan.atoomic/implement-check-is-null rebased onto main and force-pushed.

Diff: 3 files changed, 233 insertions(+), 15 deletions(-)

Review feedback was analyzed and applied.

Actions

• Resolved merge conflicts (1 round(s))
• Rebased koan.atoomic/implement-check-is-null onto upstream/main
• Force-pushed koan.atoomic/implement-check-is-null to origin
• CI check enqueued (async)

CI

CI will be checked asynchronously.

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Automated by Kōan

[atoomic]

Failure from smokers

Run make test
"/usr/local/bin/perl" -MExtUtils::Command::MM -e 'cp_nonempty' -- FileCheck.bs blib/arch/auto/Overload/FileCheck/FileCheck.bs 644
PERL_DL_NONLAZY=1 "/usr/local/bin/perl" "-MExtUtils::Command::MM" "-MTest::Harness" "-e" "undef *Test::Harness::Switches; test_harness(0, 'blib/lib', 'blib/arch')" t/*.t
t/00-load.t .......................... ok
t/01_boot.t .......................... ok
t/02_basic-mock.t .................... ok
t/02_import.t ........................ ok

# Failed test '42'
# at t/check-null.t line 86.
# +--------------+----+-------+
# | GOT          | OP | CHECK |
# +--------------+----+-------+
# | /null-test-s | eq | 42    |
# +--------------+----+-------+
(If this table is too small, you can use the TABLE_TERM_SIZE=### env var to set a larger size, detected size is '78')

# -s returns the mocked size

# Failed test '0'
# at t/check-null.t line 89.
# +--------------+----+-------+
# | GOT          | OP | CHECK |
# +--------------+----+-------+
# | /null-test-s | eq | 0     |
# +--------------+----+-------+
(If this table is too small, you can use the TABLE_TERM_SIZE=### env var to set a larger size, detected size is '78')

# -s returns 0 when size is 0
# Seeded srand with seed '20260327' from local date.
t/check-null.t ....................... 
Dubious, test returned 2 (wstat 512, 0x200)
Failed 2/18 subtests 
t/exporter-all.t ..................... ok
t/exporter.t ......................... ok
t/fh-ref-leak.t ...................... ok
t/issue-0001.t ....................... ok
t/mock-all-file-checks.t ............. ok
t/mock-all-from-stat.t ............... ok
t/mock-all-from-stat_advanced.t ...... ok
t/mock-all-from-stat_basic.t ......... ok
t/mock-lstat.t ....................... ok
t/mock-setting-errno.t ............... ok
t/mock-stat.t ........................ ok
t/recycle-stat.t ..................... ok
t/simple-test.t ...................... ok
t/stack-corruption.t ................. ok
t/stat-errno-preservation.t .......... ok
t/stat-helpers-invalid-user-group.t .. ok
# Running privileged (root/root)
t/stat-helpers.t ..................... ok
t/stat-key-normalization.t ........... ok
t/test-A.t ........................... ok
t/test-B-uppercase.t ................. ok
t/test-b.t ........................... ok
t/test-C-uppercase.t ................. ok
t/test-c.t ........................... ok
t/test-d.t ........................... ok
t/test-e-simple.t .................... ok
t/test-e.t ........................... ok
t/test-f.t ........................... ok
t/test-g.t ........................... ok
t/test-integer.t ..................... skipped: This test is designed to be run from one of the symlink: t/test-s.t ...
t/test-k.t ........................... ok
t/test-l.t ........................... ok
t/test-M.t ........................... ok
t/test-O-uppercase.t ................. ok
t/test-o.t ........................... ok
t/test-p.t ........................... ok
t/test-R-uppercase.t ................. ok
t/test-r.t ........................... ok
t/test-S-uppercase.t ................. ok
t/test-s.t ........................... ok
t/test-T-uppercase.t ................. ok
t/test-t.t ........................... ok
t/test-true-false.t .................. skipped: This test is designed to be run from one of the symlink: t/test-e.t ...
t/test-u.t ........................... ok
t/test-W-uppercase.t ................. ok
t/test-w.t ........................... ok
t/test-X-uppercase.t ................. ok
t/test-x.t ........................... ok
t/test-z.t ........................... ok
t/xt-author-check-examples.t ......... ok

Test Summary Report
-------------------
t/check-null.t                     (Wstat: 512 (exited 2) Tests: 18 Failed: 2)
  Failed tests:  7-8
  Non-zero exit status: 2
t/mock-all-from-stat_advanced.t    (Wstat: 0 Tests: 245 Failed: 0)
  TODO passed:   6, 18, 49, 61, 74, 173, 188, 203, 218, 233
t/simple-test.t                    (Wstat: 0 Tests: 14 Failed: 0)
  TODO passed:   3, 5
Files=54, Tests=1349,  4 wallclock secs ( 0.13 usr  0.10 sys +  3.14 cusr  0.75 csys =  4.12 CPU)
Result: FAIL

@Koan-Bot rebase

[Koan-Bot]

Rebase: feat: implement CHECK_IS_NULL handling for undef mock returns

Branch koan.atoomic/implement-check-is-null rebased onto main and force-pushed.

Diff: 3 files changed, 234 insertions(+), 6 deletions(-)

Review feedback was analyzed and applied.

Actions

• Resolved merge conflicts (4 round(s))
• Rebased koan.atoomic/implement-check-is-null onto upstream/main
• Force-pushed koan.atoomic/implement-check-is-null to origin
• CI check enqueued (async)

CI

CI will be checked asynchronously.

---

Automated by Kōan

[atoomic]

Failures from Perl 5.10, 5.12 and 5.14 on smokers view https://github.com/cpan-authors/Overload-FileCheck/actions/runs/23694139455/job/69026556441?pr=39 for more details

Test Summary Report
-------------------
t/check-null.t                     (Wstat: 512 (exited 2) Tests: 18 Failed: 2)
  Failed tests:  7-8
  Non-zero exit status: 2
t/mock-all-from-stat_advanced.t    (Wstat: 0 Tests: 245 Failed: 0)
  TODO passed:   6, 18, 49, 61, 74, 173, 188, 203, 218, 233
t/simple-test.t                    (Wstat: 0 Tests: 14 Failed: 0)
  TODO passed:   3, 5

@Koan-Bot rebase

[Koan-Bot]

Rebase: feat: implement CHECK_IS_NULL handling for undef mock returns

Branch koan.atoomic/implement-check-is-null rebased onto main and force-pushed.

Diff: 3 files changed, 240 insertions(+), 6 deletions(-)

Review feedback was analyzed and applied.

Changes

Fix applied. The -s file-test operator inside is() function calls gets misparsed on some Perl versions — the tokenizer consumes arguments differently when -s EXPR appears directly as a function argument. The existing test suite (test-integer.t) already handles this by using eval or temp variables.

Summary for commit message:

• Fix -s operator parsing ambiguity in t/check-null.t (lines 86, 89): assign -s result to a temp variable before passing to is(), matching the pattern used by existing tests in test-integer.t. The Perl tokenizer misparsed -s "/path" as a direct argument to is() on CI smokers, causing the filename string to be compared instead of the file-test result.

Actions

• Already-solved check: negative (confidence=high, reasoning=CHECK_IS_NULL is exported on main but never acted on — the XS undef detection (-2 sentinel) and PP h)
• Resolved merge conflicts (1 round(s))
• Rebased koan.atoomic/implement-check-is-null onto upstream/main
• Applied review feedback
• Force-pushed koan.atoomic/implement-check-is-null to origin
• CI check enqueued (async)

CI

CI will be checked asynchronously.

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Automated by Kōan