1 Commits
Author SHA1 Message Date
glenn schrooyenandClaude Opus 5 7b4877d56d TEST-15: purge the bytecode cache before a mutation run, not after
checks / unit (pull_request) Successful in 3m35s
FCST-03's developer reverted `self.provisional` to `here.provisional`, re-ran,
and reported the mutation as a survivor. It was not one. CPython validates a
cached `.pyc` on (source size, source mtime truncated to whole seconds), and
that edit moved neither number - same length, same second - so the interpreter
loaded the bytecode it already had. Disassembly settled it at the time: the
source read `here`, the running code loaded `self`. A mutation run had graded
code that was not there, with no error and exit status 0.

This does not make the results already on the record wrong. It makes them
UNVERIFIED, and that distinction is the whole card - so nothing here re-runs a
campaign and nothing here quietly assumes the old numbers hold.

REPRODUCED, THEN CLOSED. test_bytecode.py builds a real package whose two
return values are the same length, imports it in a real subprocess, rewrites it
inside the same second (retrying until both writes land in one whole second -
milliseconds, no sleep) and reads back which value ran. Part 1 shows the
interpreter running SELF off a file that says HERE.

AND THE TWO OBVIOUS MITIGATIONS DO NOT WORK. Measured, not read off
documentation: `python3 -B` and PYTHONDONTWRITEBYTECODE=1 are write-side only.
Neither stops an EXISTING stale .pyc being read, and a mutation run always has
one, because the previous run wrote it. Part 2 grades both still running the old
code. The advice in test_control.py's coverage audit led with `-B`; it is
corrected here - the purge is the half that works, and `-B` earns its place by
keeping THIS run from leaving a cache for the NEXT edit to inherit.

NO SLEEP ANYWHERE. One-second mtime resolution is the mechanism, not the enemy.
Waiting it out would slow every run down and would still only cover the edit
somebody remembered to slow down.

THE HARNESS. tools/mutation_run.sh purges, prints a sha256/byte fingerprint of
every app/*.py it is about to grade - so a mutation report can say WHICH source
produced it, which is the reviewer's addition to this card - runs each suite
under `python3 -B`, refuses a tree with no test_*.py (CI-01's rule, for CI-01's
reason), and fails if a cache appears during the run. It takes the tree as an
argument so the infra repo's replay harnesses can call it without being moved.

WHERE IT IS SAID (AC 2). MUTATION.md carries the mechanism, the measurement,
the reporting rules and the survey, and every one of the 16 suites now points at
it from its docstring. That list is DERIVED FROM THE TREE by test_bytecode.py
part 5, so a new suite that joins this directory without the pointer is red -
the same failure shape CI-01's file glob exists to prevent.

CI WAS ALREADY IMMUNE, AND IS DESCRIBED THAT WAY (AC 4). Verified rather than
reasoned: with the checkout bind mounted `-v "$WS:/w:ro"` the interpreter writes
no __pycache__ into the tree at all, and it fails SILENTLY - no error, exit
status 0 - while the same probe on a writable mount produces one. Each job also
rm -rf's its workspace and clones afresh, so nothing crosses between jobs on the
shared runner. PYTHONDONTWRITEBYTECODE=1 is added as belt and braces only: the
`:ro` is one character wide and the next person debugging a write will be
tempted by it. Part 6 grades both ON THE DOCKER COMMAND LINE rather than on the
file - the first draft searched the whole workflow and stayed green after the
flag was deleted, because the comment explaining it still named it.

THE SHIPPED ADD-ON IS NOT AFFECTED and the question is closed:
goodwe_controller/Dockerfile has set PYTHONDONTWRITEBYTECODE=1 since it was
written. There is no deploy-side finding.

THE SURVEY (AC 3), in MUTATION.md, scoped BY THE PROPERTY. The defect is
one-directional - a mutation that never took leaves the suite green, so stale
bytecode manufactures SURVIVORS and cannot manufacture a red - which puts every
"all red, no survivors" claim in the window out of scope, along with mutations
executed in-process (SAFETY-07's B1/B2/B3, test_peakguard parts 7 and 10, where
no source file is edited) and everything run after the purge discipline landed
on 2026-08-31 (SAFETY-24, SAFETY-26, OPT-04, FCST-03's re-run). What is left is
the recorded SURVIVORS from source-edit runs before that date. Two were re-run
here under the harness and both still stand: TARIFF-01's record_block() ignoring
its policy argument, and SAFETY-03's abs() on the clamp limit - 15 suites green
each, on the tree as it stood. The rest are labelled still-unverified rather
than assumed or re-run; each is one harness run to close, and the moment to
spend it is when somebody next touches that module.

OUT OF SCOPE AND RECORDED: the infra repo's sim/ replay harnesses import the
add-on and write bytecode into both trees (goodwe/sim/__pycache__ exists today),
so SAFETY-02's headline replay carries the same exposure. mutation_run.sh takes
a tree argument for exactly that, but the change belongs in that repo and some
of those harnesses want the rig.

RED AND GREEN. Every new check was broken and watched fail: the purge commented
out of the harness turns part 4 red (and its non-vacuity probe already proves
the fixture would mis-grade without it); one docstring pointer removed turns
part 5 red naming the file; `:ro` and the `-e` flag removed from the workflow
turn part 6 red. Full suite green, 16 files, in the CI image on a read-only
mount - the shape the runner uses.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-09-01 02:07:09 +02:00