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ersatztv/scripts/tests/test_hook_fire_log.py
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timothyandtimothy d4c72697f2
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feat(780): commit a ruff config and enforce it in CI (#813)
Python lint here was a property of the operator's laptop: the global instructions
say to run ruff, no workflow ran it, and with no committed config ruff fell back
to whichever ~/.config/ruff/ruff.toml the machine happened to have.

- ruff.toml at the root, pinned ruff==0.12.11 in the script-tests job.
- Both lint steps pass an EXPLICIT population from `git ls-files` with
  `--no-force-exclude`, never `ruff check .` — an `exclude` empties a
  discovery-based run into a GREEN one (top level empties both commands, [lint]
  empties check, [format] empties format --check), and `ruff check .` over zero
  files exits 0 with only a stderr warning. Guarded by an empty-population arm.
- Tree clean: 74 findings at 706674272, 57 fixed in code, 17 per-site noqa with
  reasons inline. S105 deliberately per-site, not a directory blanket. RUF100
  selected so a suppression that suppresses nothing is itself a finding.
- pyright stays ungated; reasoning in the record.

Both steps witnessed red on the runner against the shipped bodies: run 2173 job
9176 (ruff check) and run 2170 job 9163 (ruff format --check).

Docs: new record ci.python-lint-ruff-config-committed, ci.script-tests-job
cross-ref, docs/ci-cd.md (also correcting a stale ~190-tests/~10s figure to the
measured 773 tests / ~4.5 min), docs/defect-shapes-773.md §5.2 resolved.

fixes #780

Co-authored-by: Timothy <timothy@noreply.gitea.tblindustries.be>
2026-08-22 00:33:18 +00:00

1639 lines
74 KiB
Python

"""Every hook reports that it fired, and the reporting changes nothing else (ersatztv#776).
Two separable claims, and conflating them is how instrumentation ships as a regression:
1. COVERAGE — every hook script records its own execution. The population is DERIVED from
`.claude/hooks/*.sh`, never listed, per `testing.guard-derives-population-from-source`, so a
hook added tomorrow is uninstrumented-and-red rather than silently unobserved.
2. TRANSPARENCY — the wrapper is invisible to the harness. It slurps stdin and replays it, and it
diverts stdout and replays it, which puts it directly in the path of the most load-bearing
guards in this repo. If it drops a byte of a `deny` payload or swallows an exit code, it
disables a guard while reporting that the guard fired. That is strictly worse than the
blindness #776 set out to fix, so the differential test below drives EVERY hook, with and
without the instrumentation, over a payload matrix and demands byte-equal stdout and equal
exit status.
The mutation proof for claim 1 is the contrapositive form allowed by
`testing.guard-ships-with-mutation-proof` for a checker-guard: the defect the guard exists to catch
(an uninstrumented hook) is introduced into an isolated copy of the guarded artifact, and the named
check must go red. See `test_a_hook_that_LOSES_its_instrumentation_is_DETECTED`.
Claim 2's proof is not a mutation of an assertion but a real A/B over the real scripts, which is the
only thing that can establish it — a unit test of the wrapper in isolation would pass on a wrapper
that is fine alone and lethal in context.
"""
from __future__ import annotations
import os
import pty
import re
import subprocess
from pathlib import Path
import pytest
REPO_ROOT = Path(__file__).resolve().parents[2]
HOOKS_DIR = REPO_ROOT / ".claude" / "hooks"
SINK = REPO_ROOT / "scripts" / "hook-fire-log.sh"
# The three lines a hook must carry. Matched structurally rather than as one frozen blob so that a
# comment reflow does not redden the suite, but the two things that matter — sourcing the single
# shared sink, and calling begin with this hook's own name — are both pinned.
_SOURCES_SINK = re.compile(r'^\[ -r "\$ETV_HOOK_FIRE_LIB" \] && \. "\$ETV_HOOK_FIRE_LIB" \|\| true$', re.M)
_BEGINS = re.compile(r"^etv_hook_fire_begin (\S+) .*\|\| true$", re.M)
def hook_scripts() -> list[Path]:
"""THE POPULATION, from the filesystem. Never a list."""
return sorted(HOOKS_DIR.glob("*.sh"))
def expected_mode(name: str) -> str:
"""DERIVED from the wiring, not listed.
A hook registered in `.claude/settings.json` is a Claude hook: it always exits 0 and decides by
PRINTING JSON, so its stdout must be captured or the decision is unobservable. A hook registered
in `.husky/*` is a git hook: it decides by exit status and its stdout is progress text a human
watches live, so capturing it would hold the output back until the end.
Reading this from the settings files rather than a hardcoded set means a hook that changes
wiring gets the right expectation automatically — and, unlike a list, it cannot be quietly
edited to match a mistake.
"""
if name in (REPO_ROOT / ".claude" / "settings.json").read_text():
return "capture"
for husky in (REPO_ROOT / ".husky").iterdir():
if husky.is_file() and name in husky.read_text():
return "stream"
return "capture"
def instrumentation_faults(text: str, name: str) -> list[str]:
"""The check itself, factored out so a mutation can be fed to the same code the suite runs."""
faults = []
if not _SOURCES_SINK.search(text):
faults.append(f"{name}: does not source scripts/hook-fire-log.sh")
# The sink PATH, not just the sourcing line. Repointing `ETV_HOOK_FIRE_LIB` at /dev/null leaves
# the `[ -r ] && .` line untouched and disables all reporting silently — a mutation the first
# version of this checker passed clean.
lib = re.search(r"^ETV_HOOK_FIRE_LIB=(.*)$", text, re.M)
if not lib:
faults.append(f"{name}: no ETV_HOOK_FIRE_LIB assignment")
elif "/scripts/hook-fire-log.sh" not in lib.group(1):
faults.append(f"{name}: ETV_HOOK_FIRE_LIB does not point at the shared sink: {lib.group(1)}")
# A hook that disables its own reporting reads as instrumented and reports nothing.
if re.search(r"^\s*(export\s+)?ETV_HOOK_FIRE_DISABLE=1", text, re.M):
faults.append(f"{name}: sets ETV_HOOK_FIRE_DISABLE=1, so it never reports")
m = _BEGINS.search(text)
if not m:
faults.append(f"{name}: never calls etv_hook_fire_begin")
elif m.group(1) != name:
faults.append(f"{name}: calls etv_hook_fire_begin for {m.group(1)!r}, not for itself")
else:
# MODE. Flipping a Claude hook from `capture` to `stream` stops its stdout being read, so
# every decision it makes is recorded as `pass`/`blocked` from the exit status it never
# uses — the log stays full and becomes wrong. Nothing else in the suite notices.
mode = re.search(rf"^etv_hook_fire_begin {re.escape(name)} \S+ (\S+)", text, re.M)
want = expected_mode(name)
if not mode:
faults.append(f"{name}: etv_hook_fire_begin names no stdout mode")
elif mode.group(1) != want:
faults.append(f"{name}: begins in {mode.group(1)!r} mode but its wiring implies {want!r}")
# Order is the whole point: 8 of the hooks slurp stdin with `input=$(cat)`, and a begin
# placed after that read would find the pipe already drained — recording a fire with no
# tool name, and replaying nothing into a hook that has already consumed its payload.
stdin_read = text.find("$(cat)")
if 0 <= stdin_read < m.start():
faults.append(f"{name}: reads stdin before etv_hook_fire_begin")
return faults
def strip_instrumentation(text: str) -> str:
"""Reconstruct the pre-#776 script. Used BOTH as the mutation and as the A/B control.
The blank line that separates the preamble from the code above it is dropped too. Leaving it
made the reconstruction differ from the original by one blank line in all 13 hooks — harmless
behaviourally, but the A/B control is only trustworthy insofar as it IS the original, and
"differs only in ways I judged harmless" is a claim, not a property.
`test_the_stripper_reproduces_the_ORIGINAL_byte_for_byte` turns it into a property.
"""
out, skipping = [], False
for line in text.splitlines(keepends=True):
if line.startswith("# ersatztv#776 —"):
skipping = True
if out and out[-1].strip() == "":
out.pop()
continue
if skipping:
if line.startswith(
("#", "ETV_HOOK_FIRE_LIB=", "[ -r ", "type etv_hook_fire_begin", "etv_hook_fire_begin ")
):
continue
skipping = False
out.append(line)
return "".join(out)
# ------------------------------------------------------------------------------------------------
# ANTI-VACUITY FIRST — a glob that stopped matching would make every assertion below iterate over
# nothing and report full coverage. That is the characteristic failure of a completeness check, and
# this repo has shipped it (#631, #751), so it is asserted before anything depends on it.
# ------------------------------------------------------------------------------------------------
def test_the_population_is_not_empty():
hooks = hook_scripts()
assert len(hooks) >= 10, (
f"only found {len(hooks)} hook scripts under {HOOKS_DIR} — the glob has stopped matching, "
"so every coverage assertion in this file is vacuous."
)
assert SINK.exists(), "the shared sink is missing; the instrumentation cannot work"
assert os.access(SINK, os.X_OK), "the sink is not executable, so its report side cannot be run"
def test_the_stripper_removes_EXACTLY_the_preamble_and_nothing_else():
"""The A/B control must be the hook minus the instrumentation — no more, no less.
This compared `strip_instrumentation(hook)` against the hook at the merge base, which asserted
two unrelated things at once: that the stripper is exact, AND that no hook was edited in this PR
for any other reason. The second is not a property worth pinning — it went red the moment
`pretooluse-bom-guard.sh` had a real defect fixed (`xxd`, absent on the CI runner, made it
fail open) — and coupling them means a legitimate change reads as a broken control.
The property that actually protects the differential is structural: every line the stripper
removes is a preamble line, and it adds nothing. Checked without reference to history, so it
holds on any branch and on any platform.
"""
import difflib
allowed = (
"# ersatztv#776",
"# git hook:",
"# Claude hook:",
"ETV_HOOK_FIRE_LIB=",
'[ -r "$ETV_HOOK_FIRE_LIB"',
"type etv_hook_fire_begin",
"etv_hook_fire_begin ",
)
for hook in hook_scripts():
cur = hook.read_text().splitlines(keepends=True)
stripped = strip_instrumentation("".join(cur)).splitlines(keepends=True)
for line in difflib.Differ().compare(cur, stripped):
if line.startswith("+ "):
raise AssertionError(f"{hook.name}: the stripper ADDED a line: {line[2:]!r}")
if line.startswith("- "):
body = line[2:]
assert body.strip() == "" or body.startswith(allowed), (
f"{hook.name}: the stripper removed a NON-preamble line, so the A/B control is "
f"not this hook: {body!r}"
)
def test_the_stripper_actually_strips():
"""The A/B control and the mutation are the same function. If it were a no-op, the differential
test would compare each hook against itself and pass on a wrapper that breaks everything."""
for hook in hook_scripts():
text = hook.read_text()
stripped = strip_instrumentation(text)
assert stripped != text, f"{hook.name}: strip_instrumentation() removed nothing"
assert "etv_hook_fire_begin" not in stripped, f"{hook.name}: begin survived the strip"
assert not instrumentation_faults(text, hook.stem), f"{hook.name} is not instrumented"
# ------------------------------------------------------------------------------------------------
# CLAIM 1 — COVERAGE
# ------------------------------------------------------------------------------------------------
def test_every_hook_reports_that_it_fired():
faults = []
for hook in hook_scripts():
faults += instrumentation_faults(hook.read_text(), hook.stem)
assert not faults, (
"these hooks do not report their own execution:\n "
+ "\n ".join(faults)
+ "\n\nAdd the three-line preamble after the `set -` line and BEFORE any stdin read. A hook "
"that does not report is one whose firing we can only infer, which is ersatztv#776."
)
def test_a_hook_that_LOSES_its_instrumentation_is_DETECTED():
"""THE MUTATION PROOF (contrapositive form, for a checker-guard).
Introduce the defect this guard exists to catch — an uninstrumented hook — into an isolated copy
of each hook in turn, and the check must report it. Every hook, not a sample: the interesting
loss is whichever file someone actually edits.
"""
for hook in hook_scripts():
mutated = strip_instrumentation(hook.read_text())
faults = instrumentation_faults(mutated, hook.stem)
assert faults, (
f"stripping the instrumentation from {hook.name} left the check GREEN. The check is "
"not load-bearing — it would not notice a hook silently losing its reporting."
)
def test_begin_placed_AFTER_the_stdin_read_is_DETECTED():
"""The subtler mutation: present but too late. Ordering is the property that makes it work."""
late = 'set -euo pipefail\ninput=$(cat)\nETV_HOOK_FIRE_LIB="x"\n[ -r "$ETV_HOOK_FIRE_LIB" ] && . "$ETV_HOOK_FIRE_LIB" || true\netv_hook_fire_begin demo "" capture || true\n' # noqa: E501 - kept on one line so the fixture is greppable against the payload the hook receives
faults = instrumentation_faults(late, "demo")
assert any("reads stdin before" in f for f in faults), (
"a begin call placed after `input=$(cat)` was accepted. It would record a fire with no "
f"payload and replay nothing. faults={faults}"
)
# ------------------------------------------------------------------------------------------------
# CLAIM 2 — TRANSPARENCY. The wrapper must be invisible to the harness.
# ------------------------------------------------------------------------------------------------
# A BROAD, CHEAP matrix. It reaches the deciding branch of only a few hooks; the ones it cannot
# reach with a bare payload get a constructed positive case in `positive_cases()` below, and
# `test_the_AB_is_not_VACUOUS_for_any_hook` refuses to let any hook rely on this matrix alone.
#
# Stated because the first version of this file claimed the opposite in three places: this matrix
# alone produced empty-vs-empty comparisons for 8 of 13 hooks and a zero exit status for all 13, so
# deleting the entire stdout replay left the differential test green for four hooks — two of which
# issue `deny`. An A/B over silent allows proves transparency on the one path where there is nothing
# to be transparent about.
PAYLOADS = {
"bash-deny": '{"session_id":"s","hook_event_name":"PreToolUse","tool_name":"Bash","cwd":"%(cwd)s","tool_input":{"command":"ETV_UPDATE_GOLDENS=1 dotnet test"}}', # noqa: E501 - kept on one line so the fixture is greppable against the payload the hook receives
"bash-allow": '{"session_id":"s","hook_event_name":"PreToolUse","tool_name":"Bash","cwd":"%(cwd)s","tool_input":{"command":"ls -la"}}', # noqa: E501 - kept on one line so the fixture is greppable against the payload the hook receives
"git-commit": '{"session_id":"s","hook_event_name":"PreToolUse","tool_name":"Bash","cwd":"%(cwd)s","tool_input":{"command":"git commit -m x"}}', # noqa: E501 - kept on one line so the fixture is greppable against the payload the hook receives
"nav-deny": '{"session_id":"s","hook_event_name":"PreToolUse","tool_name":"mcp__x__navigate","cwd":"%(cwd)s","tool_input":{"url":"http://h/iptv/channels.m3u"}}',
"agent-no-model": '{"session_id":"s","hook_event_name":"PreToolUse","tool_name":"Agent","cwd":"%(cwd)s","tool_input":{"description":"d","prompt":"p"}}', # noqa: E501 - kept on one line so the fixture is greppable against the payload the hook receives
"agent-model": '{"session_id":"s","hook_event_name":"PreToolUse","tool_name":"Agent","cwd":"%(cwd)s","tool_input":{"description":"d","prompt":"p","model":"sonnet"}}', # noqa: E501 - kept on one line so the fixture is greppable against the payload the hook receives
"merge": '{"session_id":"s","hook_event_name":"PreToolUse","tool_name":"mcp__gitea__pull_request_write","cwd":"%(cwd)s","tool_input":{"method":"merge","owner":"timothy","repo":"ersatztv","pull_number":1}}', # noqa: E501 - kept on one line so the fixture is greppable against the payload the hook receives
"worktree-add": '{"session_id":"s","hook_event_name":"PostToolUse","tool_name":"Bash","cwd":"%(cwd)s","tool_input":{"command":"git worktree add /tmp/nope-%(nonce)s HEAD"}}', # noqa: E501 - kept on one line so the fixture is greppable against the payload the hook receives
"ui-edit": '{"session_id":"s","hook_event_name":"PreToolUse","tool_name":"Edit","cwd":"%(cwd)s","tool_input":{"file_path":"web/src/screens/Channels.tsx"}}', # noqa: E501 - kept on one line so the fixture is greppable against the payload the hook receives
"empty": "",
"garbage": "not json at all",
}
@pytest.fixture(scope="module")
def sandbox(tmp_path_factory):
"""A controlled environment so the A/B pair cannot differ for reasons unrelated to the wrapper.
`memory_pressure` is stubbed because `pretooluse-agent-ram.sh` reads live free RAM: a real
reading that crossed the 10% or 20% threshold between the two runs would make the A and B halves
disagree for a reason that has nothing to do with instrumentation, and a differential test that
flakes is one that gets rerun until green.
"""
root = tmp_path_factory.mktemp("hookfire")
bindir = root / "bin"
bindir.mkdir()
stub = bindir / "memory_pressure"
stub.write_text("#!/bin/sh\necho 'System-wide memory free percentage: 42%'\n")
stub.chmod(0o755)
env = dict(os.environ)
env["PATH"] = f"{bindir}:{env['PATH']}"
env["ETV_HOOK_FIRE_LOG_DIR"] = str(root / "log")
env["CLAUDE_PROJECT_DIR"] = str(REPO_ROOT)
# No creds: `pretooluse-merge-consent.sh` must take its documented "cannot derive state" path
# rather than making live Gitea calls from a unit test.
for k in ("ETV_GITEA_TOKEN", "ETV_GITEA_BASICAUTH"):
env.pop(k, None)
return root, env
def _run(script: Path, payload: str, env: dict, cwd: Path, arg: str | None = None):
cmd = ["bash", str(script)] + ([arg] if arg else [])
p = subprocess.run(cmd, input=payload.encode(), capture_output=True, cwd=str(cwd), env=env, timeout=60)
return p.returncode, p.stdout
def _git(cwd: Path, *args: str) -> None:
subprocess.run(
["git", *args],
cwd=str(cwd),
check=True,
capture_output=True,
env={
**os.environ,
"GIT_AUTHOR_NAME": "t",
"GIT_AUTHOR_EMAIL": "t@e",
"GIT_COMMITTER_NAME": "t",
"GIT_COMMITTER_EMAIL": "t@e",
},
)
@pytest.fixture(scope="module")
def positives(sandbox, tmp_path_factory):
"""CONSTRUCTED cases that drive hooks the bare payload matrix cannot reach to a DECIDING branch.
Each entry is (case-name, payload, arg, env, cwd). Building real git repositories is the point:
the hooks these cover — the BOM guard, the worktree-ownership guard, the three pre-push guards —
all decide by inspecting a repository, so a payload alone can only ever reach their early exit.
"""
_root, base_env = sandbox
w = tmp_path_factory.mktemp("positives")
cases: dict[str, list[tuple]] = {}
def pay(**kw) -> str:
import json as _json
return _json.dumps({"session_id": "me", "hook_event_name": "PreToolUse", "tool_name": "Bash", **kw})
# --- worktree-guard: a marker naming ANOTHER session, on a `git commit` -------------------
wt = w / "sibling"
wt.mkdir()
_git(wt, "init", "-q", ".")
(wt / ".claude-worktree-owner").write_text("SOME-OTHER-SESSION\n")
cases["pretooluse-worktree-guard"] = [
(
"foreign-marker-deny",
pay(cwd=str(wt), tool_input={"command": "git commit -m x"}),
None,
base_env,
wt,
)
]
# --- bom-guard: repo path must match `*ersatztv*`, with a staged BOM-carrying .cs ----------
br = w / "ersatztv-scratch"
br.mkdir()
_git(br, "init", "-q", ".")
(br / "Bad.cs").write_bytes(b"\xef\xbb\xbfclass A {}\n")
_git(br, "add", "Bad.cs")
cases["pretooluse-bom-guard"] = [
(
"staged-bom-deny",
pay(cwd=str(br), tool_input={"command": "git commit -m x"}),
None,
base_env,
br,
)
]
# --- agent-ram: both thresholds, via a stubbed `memory_pressure` ---------------------------
ram_cases = []
for pct, label in ((5, "deny"), (15, "ask")):
bindir = w / f"bin{pct}"
bindir.mkdir()
stub = bindir / "memory_pressure"
stub.write_text(f"#!/bin/sh\necho 'System-wide memory free percentage: {pct}%'\n")
stub.chmod(0o755)
env = dict(base_env)
env["PATH"] = f"{bindir}:{os.environ['PATH']}"
ram_cases.append(
(
f"free-{pct}pct-{label}",
pay(tool_name="Agent", cwd=str(w), tool_input={"prompt": "p", "model": "sonnet"}),
None,
env,
w,
)
)
cases["pretooluse-agent-ram"] = ram_cases
# --- decisions-guard: a validator that prints and blocks, and one that prints and passes ---
dg = w / "dg"
(dg / "scripts").mkdir(parents=True)
_git(dg, "init", "-q", ".")
dg_cases = []
for rc, label in ((1, "block"), (0, "pass")):
d = w / f"dg{rc}"
(d / "scripts").mkdir(parents=True)
_git(d, "init", "-q", ".")
(d / "scripts" / "decisions_validate.py").write_text(
f"import sys\nprint('VALIDATOR SAID SOMETHING')\nsys.exit({rc})\n"
)
dg_cases.append((f"validator-{label}", "", None, base_env, d))
cases["decisions-guard"] = dg_cases
# --- pre-push guards: a real remote, so `git fetch origin main` resolves -------------------
bare = w / "remote.git"
_git(w, "init", "-q", "--bare", "--initial-branch=main", str(bare))
def clone(name: str) -> Path:
p = w / name
subprocess.run(["git", "clone", "-q", str(bare), str(p)], check=True, capture_output=True)
_git(p, "config", "user.email", "t@e")
_git(p, "config", "user.name", "t")
return p
seed = clone("seed")
(seed / "file.txt").write_text("one\n")
_git(seed, "add", "-A")
_git(seed, "commit", "-qm", "seed")
_git(seed, "push", "-q", "origin", "main")
# rebase-check: local HEAD is an ANCESTOR of a since-advanced origin/main -> blocks.
behind = clone("behind")
_git(behind, "checkout", "-qb", "feat")
ahead = clone("ahead")
(ahead / "file.txt").write_text("two\n")
_git(ahead, "add", "-A")
_git(ahead, "commit", "-qm", "advance main")
_git(ahead, "push", "-q", "origin", "main")
head = subprocess.run(["git", "rev-parse", "HEAD"], cwd=str(behind), capture_output=True, text=True).stdout.strip()
cases["prepush-rebase-check"] = [
(
"behind-origin-main-blocks",
f"refs/heads/feat {head} refs/heads/feat {'0' * 40}\n",
None,
base_env,
behind,
)
]
# clean-worktree-check: a file both MODIFIED in the tree and present in the pushed set.
dirty = clone("dirty")
(dirty / "file.txt").write_text("committed change\n")
_git(dirty, "add", "-A")
_git(dirty, "commit", "-qm", "change file")
(dirty / "file.txt").write_text("uncommitted change\n")
dhead = subprocess.run(["git", "rev-parse", "HEAD"], cwd=str(dirty), capture_output=True, text=True).stdout.strip()
cases["prepush-clean-worktree-check"] = [
(
"dirty-file-in-pushed-set-blocks",
f"refs/heads/main {dhead} refs/heads/main {'0' * 40}\n",
None,
base_env,
dirty,
)
]
# --- prepush-donewhen: a push to main closing an issue with an unticked Done-when box -------
#
# This one needs a Gitea, so it gets a stub HTTP server rather than an exemption. Without it the
# hook's only reachable path in a test is its no-creds fail-open, and the guard that blocks
# pushes to `main` would be the one hook whose transparency nothing checks — precisely the
# "covered everywhere except where it matters" shape this repo keeps paying for.
import http.server
import json as _json
import threading
body = _json.dumps({"body": "## Done-when\n\n- [ ] not finished\n- [x] finished\n"}).encode()
class _Stub(http.server.BaseHTTPRequestHandler):
def do_GET(self):
self.send_response(200)
self.send_header("Content-Type", "application/json")
self.send_header("Content-Length", str(len(body)))
self.end_headers()
self.wfile.write(body)
def log_message(self, *a): # keep pytest output clean
pass
srv = http.server.HTTPServer(("127.0.0.1", 0), _Stub)
threading.Thread(target=srv.serve_forever, daemon=True).start()
dw = clone("donewhen")
(dw / "src.cs").write_text("class A {}\n") # NOT docs-only, so the exemption does not apply
_git(dw, "add", "-A")
_git(dw, "commit", "-qm", "feat: thing\n\nfixes #999")
dw_head = subprocess.run(["git", "rev-parse", "HEAD"], cwd=str(dw), capture_output=True, text=True).stdout.strip()
dw_prev = subprocess.run(["git", "rev-parse", "HEAD~1"], cwd=str(dw), capture_output=True, text=True).stdout.strip()
dw_env = dict(base_env)
dw_env["ETV_GITEA_URL"] = f"http://127.0.0.1:{srv.server_address[1]}"
dw_env["ETV_GITEA_BASICAUTH"] = "stub:stub"
cases["prepush-donewhen"] = [
(
"unticked-donewhen-blocks-push-to-main",
f"refs/heads/main {dw_head} refs/heads/main {dw_prev}\n",
None,
dw_env,
dw,
)
]
return cases
def _ab_cases(hook: Path, sandbox, positives) -> list[tuple]:
"""(label, payload, arg, env, cwd) for the generic matrix PLUS this hook's constructed cases."""
root, env = sandbox
cases: list[tuple] = []
args = [None, "start", "finish"] if hook.stem == "design-sync-reminder" else [None]
for name, template in PAYLOADS.items():
for arg in args:
cases.append(
(
f"matrix:{name}:{arg}",
template % {"cwd": str(root), "nonce": name},
arg,
env,
root,
)
)
for label, payload, arg, penv, cwd in positives.get(hook.stem, []):
cases.append((f"positive:{label}", payload, arg, penv, cwd))
return cases
def _ab_run(hook: Path, sandbox, case, tag_root: str):
"""Run the control and the instrumented hook for one case. Returns both (rc, stdout, stderr)."""
root = sandbox[0]
control = root / f"control-{hook.name}"
if not control.exists():
control.write_text(strip_instrumentation(hook.read_text()))
control.chmod(0o755)
_label, payload, arg, env, cwd = case
# A SEPARATE TMPDIR PER SIDE, not per pair. `design-sync-reminder.sh` throttles itself with a
# marker file under $TMPDIR, so a shared one let the control fire and then silently suppress the
# instrumented run — the A/B reported a swallowed decision that was really the hook's own
# one-shot behaviour working correctly. Sharing state between the two halves of a differential
# test makes it measure the state, not the difference.
def side(t: str) -> dict:
e = dict(env)
e["TMPDIR"] = str(root / f"tmp-{tag_root}-{t}")
Path(e["TMPDIR"]).mkdir(parents=True, exist_ok=True)
return e
def one(script: Path, t: str):
cmd = ["bash", str(script)] + ([arg] if arg else [])
p = subprocess.run(cmd, input=payload.encode(), capture_output=True, cwd=str(cwd), env=side(t), timeout=90)
return p.returncode, p.stdout, p.stderr
return one(control, "control"), one(hook, "instrumented")
def _normalise_stderr(err: bytes) -> bytes:
"""Erase the two things that MUST differ between the control and the instrumented hook.
bash prefixes its own diagnostics with `$0` and a line number. The control is a copy at a
different path, and the instrumentation adds four lines to the top, so *every* bash-emitted
message differs in exactly those two fields for reasons that have nothing to do with
transparency. Only the script path and `line N:` are normalised — narrowly, so that a genuine
difference in the message body still fails.
"""
# The two fields are normalised TOGETHER, as one anchored prefix, not independently. A global
# `line \d+:` substitution also rewrites application text that happens to contain that phrase,
# and cold review demonstrated it collapsing two genuinely different diagnostics ("highest
# private fd line 0" vs "line 4") into one — hiding exactly the kind of fd-state difference this
# comparison exists to catch.
return re.sub(rb"(?m)^[^\s:]*/[^\s:]*\.sh: line \d+:", b"<script>: line <n>:", err)
@pytest.mark.parametrize("hook", hook_scripts(), ids=lambda h: h.stem)
def test_instrumentation_changes_NOTHING_the_harness_can_see(hook, sandbox, positives):
"""THE REGRESSION NET. Every hook, every case: byte-equal stdout, byte-equal stderr, equal status.
This is what stands between #776 and having silently disarmed the guard set while adding a log
that cheerfully reports every hook firing.
STDERR is compared too. It was not, and that hid a real change: when the sink is unreadable the
preamble's `etv_hook_fire_begin` was an undefined command, so the hook printed `command not
found` to stderr and the A/B could not see it. Anything the harness or a human can observe
belongs in the comparison, not just the channel the decision travels on.
"""
for i, case in enumerate(_ab_cases(hook, sandbox, positives)):
(rc_a, out_a, err_a), (rc_b, out_b, err_b) = _ab_run(hook, sandbox, case, f"{hook.stem}-{i}")
label = f"{hook.name} {case[0]}"
assert rc_a == rc_b, f"{label}: exit status changed {rc_a} -> {rc_b}"
assert out_a == out_b, f"{label}: stdout changed.\n without: {out_a!r}\n with: {out_b!r}"
na, nb = _normalise_stderr(err_a), _normalise_stderr(err_b)
assert na == nb, f"{label}: stderr changed.\n without: {na!r}\n with: {nb!r}"
@pytest.mark.parametrize("hook", hook_scripts(), ids=lambda h: h.stem)
def test_the_AB_is_not_VACUOUS_for_any_hook(hook, sandbox, positives):
"""ANTI-VACUITY FOR CLAIM 2 — the assertion the first version of this file was missing.
`test_instrumentation_changes_NOTHING_the_harness_can_see` compares the two halves against each
other. If a hook emits nothing and exits 0 on every case, that comparison is `("", 0) == ("", 0)`
and passes on a wrapper that discards all output. Measured on the original matrix: 160 of 165
comparisons were empty-vs-empty and 165 of 165 were `0 == 0`, so deleting the entire replay block
left the differential green for four hooks, two of which issue `deny`.
So each hook must have at least one case where the CONTROL side actually says something —
non-empty stdout, or a non-zero exit. The population is the hook glob, so a new hook arrives
here uncovered-and-red rather than quietly riding on a matrix that never reaches it.
ONE HOOK IS EXEMPT, and the exemption is narrow, derived and stated rather than assumed:
`posttooluse-worktree-marker.sh` emits nothing and exits 0 on every input BY DESIGN — its whole
output is a marker file. Testing it for non-empty stdout would be testing for a bug. Its
transparency is asserted instead through its side effect, in
`test_the_worktree_markers_SIDE_EFFECT_is_unchanged`.
"""
if hook.stem == "posttooluse-worktree-marker":
pytest.skip("emits nothing by design; covered by its side-effect test instead")
productive = []
for i, case in enumerate(_ab_cases(hook, sandbox, positives)):
(rc_a, out_a, _), _ = _ab_run(hook, sandbox, case, f"vac-{hook.stem}-{i}")
if out_a or rc_a != 0:
productive.append((case[0], len(out_a), rc_a))
assert productive, (
f"{hook.name}: NOT ONE case makes this hook emit output or exit non-zero, so every "
"comparison in the differential test is empty-vs-empty and it would stay green with the "
"instrumentation's entire replay path deleted. Add a constructed case to `positives()` that "
"drives this hook to its deciding branch."
)
def test_the_worktree_markers_SIDE_EFFECT_is_unchanged(sandbox, tmp_path):
"""The one hook whose whole output is a file, compared on that file rather than on stdout."""
env = sandbox[1]
hook = HOOKS_DIR / "posttooluse-worktree-marker.sh"
results = []
for tag in ("control", "instrumented"):
repo = tmp_path / tag
repo.mkdir()
_git(repo, "init", "-q", ".")
(repo / "f").write_text("x")
_git(repo, "add", "-A")
_git(repo, "commit", "-qm", "c")
target = tmp_path / f"wt-{tag}"
script = hook
if tag == "control":
script = tmp_path / "control-marker.sh"
script.write_text(strip_instrumentation(hook.read_text()))
import json as _json
payload = _json.dumps(
{
"session_id": "SESSION-XYZ",
"hook_event_name": "PostToolUse",
"tool_name": "Bash",
"cwd": str(repo),
"tool_input": {"command": f"git worktree add {target} HEAD"},
}
)
_git(repo, "worktree", "add", "-q", str(target), "HEAD")
_run(script, payload, env, repo)
marker = target / ".claude-worktree-owner"
results.append(marker.read_text() if marker.exists() else None)
assert results[0] == results[1] == "SESSION-XYZ\n", (
f"the marker the hook writes differs with and without instrumentation: {results}"
)
def test_stdout_is_replayed_BYTE_EXACT(sandbox):
"""Pinned separately from the A/B, because the A/B cannot see this class of loss.
`out=$(cat file)` strips trailing newlines, so replaying stdout through a variable delivers the
hook's JSON a newline short. Every JSON parser accepts the short form, and the A/B compares the
two halves against each other rather than against what the hook wrote — so a wrapper that
truncated BOTH would pass it. Only comparing against the literal expected bytes catches this.
"""
root, env = sandbox
hook = root / "trailing.sh"
hook.write_text(
"#!/usr/bin/env bash\nset -euo pipefail\n"
f'. "{SINK}"\n'
'etv_hook_fire_begin trailing "" capture || true\n'
"input=$(cat)\n"
r'printf "{\"hookSpecificOutput\":{\"permissionDecision\":\"deny\"}}\n\n"' + "\n"
)
rc, out = _run(hook, '{"tool_name":"Bash"}', env, root)
assert rc == 0
assert out == b'{"hookSpecificOutput":{"permissionDecision":"deny"}}\n\n', f"trailing bytes were altered: {out!r}"
@pytest.mark.parametrize("code", [0, 1, 2, 3])
def test_the_exit_code_is_preserved(sandbox, code):
"""Exit 2 is the harness's block channel and non-zero is git's. A wrapper that normalised the
status to 0 would turn every git hook into a rubber stamp while logging that it ran."""
root, env = sandbox
hook = root / f"exit{code}.sh"
hook.write_text(
"#!/usr/bin/env bash\nset -uo pipefail\n"
f'. "{SINK}"\n'
f'etv_hook_fire_begin exit{code} "" capture || true\n'
f"exit {code}\n"
)
rc, _ = _run(hook, "{}", env, root)
assert rc == code, f"exit {code} came back as {rc}"
def test_stdin_reaches_the_hook_intact(sandbox):
"""The wrapper reads stdin before the hook does. If it did not replay it faithfully, every
guard that parses `.tool_input` would see an empty payload and fail open, silently."""
root, env = sandbox
payload = '{"tool_name":"Bash","tool_input":{"command":"echo \\"quoted\\" && ls"},"session_id":"s"}'
hook = root / "echo-stdin.sh"
hook.write_text(
"#!/usr/bin/env bash\nset -euo pipefail\n"
f'. "{SINK}"\n'
'etv_hook_fire_begin echo-stdin "" capture || true\n'
"input=$(cat)\nprintf '%s' \"$input\"\n"
)
rc, out = _run(hook, payload, env, root)
assert rc == 0
assert out.decode() == payload, f"stdin was altered:\n sent: {payload}\n saw: {out.decode()}"
def test_a_TTY_stdin_is_not_slurped(sandbox):
"""The hang this nearly shipped with.
An interactive `git commit` hands its hooks a terminal on fd 0. `cat` on a tty blocks until the
user types EOF, so an unconditional slurp would freeze every commit — instrumentation hanging
the very thing it was added to observe. Driven through a real pty, because the `[ ! -t 0 ]`
guard is precisely what a pipe-based test cannot exercise.
"""
root, env = sandbox
hook = root / "tty.sh"
hook.write_text(
"#!/usr/bin/env bash\nset -uo pipefail\n"
f'. "{SINK}"\n'
'etv_hook_fire_begin ttyhook "" stream || true\n'
"echo ALIVE\n"
)
master, slave = pty.openpty()
try:
p = subprocess.Popen(
["bash", str(hook)],
stdin=slave,
stdout=subprocess.PIPE,
stderr=subprocess.DEVNULL,
cwd=str(root),
env=env,
)
os.close(slave)
try:
out, _ = p.communicate(timeout=20)
except subprocess.TimeoutExpired:
p.kill()
pytest.fail(
"the hook hung with a tty on stdin — the instrumentation slurped a terminal, "
"which would freeze every interactive `git commit`."
)
finally:
os.close(master)
assert b"ALIVE" in out
def test_logging_failure_does_not_break_the_hook(sandbox):
"""Fail-open, in the one direction that is correct here. This file is observability; if it
cannot write, the guard must still guard. The inverse — a logging bug that swallows a `deny` —
is the failure mode the A/B test above exists to prevent."""
root, env = sandbox
bad = dict(env)
bad["ETV_HOOK_FIRE_LOG_DIR"] = "/dev/null/cannot-exist"
hook = root / "failopen.sh"
hook.write_text(
"#!/usr/bin/env bash\nset -euo pipefail\n"
f'. "{SINK}"\n'
'etv_hook_fire_begin failopen "" capture || true\n'
"input=$(cat)\n"
r'printf "{\"hookSpecificOutput\":{\"permissionDecision\":\"deny\"}}"' + "\n"
)
rc, out = _run(hook, '{"tool_name":"Bash"}', bad, root)
assert rc == 0
assert out == b'{"hookSpecificOutput":{"permissionDecision":"deny"}}', (
f"an unwritable log dir changed the hook's decision output: {out!r}"
)
# ------------------------------------------------------------------------------------------------
# THE RECORD ITSELF, and the report over it
# ------------------------------------------------------------------------------------------------
@pytest.mark.parametrize(
"emit,mode,expected",
[
(r"{\"hookSpecificOutput\":{\"permissionDecision\":\"deny\"}}", "capture", "deny"),
(r"{\"hookSpecificOutput\":{\"permissionDecision\":\"ask\"}}", "capture", "ask"),
(r"{\"hookSpecificOutput\":{\"permissionDecision\":\"allow\"}}", "capture", "allow"),
(r"{\"hookSpecificOutput\":{\"additionalContext\":\"hi\"}}", "capture", "context"),
(r"{\"decision\":\"block\",\"reason\":\"r\"}", "capture", "block"),
("", "capture", "no-op"),
("", "stream", "pass"),
],
)
def test_the_recorded_decision_is_the_one_the_hook_emitted(sandbox, emit, mode, expected):
"""The decision in the log is derived from the bytes the harness receives, never from something
the hook author remembered to declare. That is the whole difference between this and inference.
"""
root, env = sandbox
logdir = root / f"log-{expected}-{mode}"
runenv = dict(env)
runenv["ETV_HOOK_FIRE_LOG_DIR"] = str(logdir)
hook = root / f"decide-{expected}-{mode}.sh"
body = f'printf "{emit}"\n' if emit else ""
hook.write_text(
"#!/usr/bin/env bash\nset -uo pipefail\n"
f'. "{SINK}"\n'
f'etv_hook_fire_begin decider "" {mode} || true\n'
"input=$(cat)\n" + body
)
rc, _ = _run(hook, '{"session_id":"sess1","tool_name":"Bash"}', runenv, root)
assert rc == 0
records = (logdir / "sess1.jsonl").read_text().splitlines()
exits = [r for r in records if '"phase":"exit"' in r]
assert len(exits) == 1, f"expected one exit record, got {records}"
assert f'"decision":"{expected}"' in exits[0], f"expected {expected} in {exits[0]}"
assert any('"phase":"fire"' in r for r in records), "no fire record was written"
def test_a_stream_mode_hook_that_BLOCKS_is_recorded_as_blocked(sandbox):
"""A git hook decides by exit code; recording a non-zero exit as `pass` would put the report
back into the business of inferring, with the answer inverted on the only path that matters."""
root, env = sandbox
logdir = root / "log-blocked"
runenv = dict(env)
runenv["ETV_HOOK_FIRE_LOG_DIR"] = str(logdir)
hook = root / "blocker.sh"
hook.write_text(
"#!/usr/bin/env bash\nset -uo pipefail\n"
f'. "{SINK}"\n'
'etv_hook_fire_begin blocker "" stream || true\n'
"input=$(cat)\nexit 1\n"
)
rc, _ = _run(hook, '{"session_id":"sess1"}', runenv, root)
assert rc == 1
assert '"decision":"blocked"' in (logdir / "sess1.jsonl").read_text()
def test_the_report_names_hooks_that_NEVER_fired(sandbox):
"""The finding #776 asks for is the ZERO row, so the report must derive its rows from the hooks
that exist rather than from the hooks that happen to appear in the log. A report built from the
log alone can only ever show hooks that fired, and would print a clean table while the broken
hook is the one missing from it."""
root, env = sandbox
logdir = root / "log-report"
logdir.mkdir()
(logdir / "sessX.jsonl").write_text(
'{"ts":"t","session":"sessX","pid":"1","hook":"pretooluse-bash-guard","label":"",'
'"event":"PreToolUse","tool":"Bash","phase":"fire","code":"","decision":""}\n'
'{"ts":"t","session":"sessX","pid":"1","hook":"pretooluse-bash-guard","label":"",'
'"event":"PreToolUse","tool":"Bash","phase":"exit","code":"0","decision":"deny"}\n'
)
p = subprocess.run(
["bash", str(SINK), "report", "--all", "--dir", str(logdir)],
capture_output=True,
cwd=str(REPO_ROOT),
env=env,
timeout=60,
)
out = p.stdout.decode()
assert p.returncode == 0, p.stderr.decode()
assert "pretooluse-bash-guard" in out and "deny=1" in out
for hook in hook_scripts():
assert hook.stem in out, (
f"{hook.stem} is absent from the report. Only hooks present in the log were listed, so "
"a hook that never fires — the finding this report exists to surface — is invisible."
)
zero_rows = [ln for ln in out.splitlines() if re.search(r"\s0\s", ln)]
assert zero_rows, "no never-fired rows shown despite only one hook appearing in the log"
def test_the_report_REFUSES_an_empty_population(tmp_path, sandbox):
"""Anti-vacuity on the read side. A report over zero hooks would print a tidy empty table and
read as 'all hooks accounted for' — the shape of #751's 6-second green.
The sink must be COPIED into a hook-less tree, not merely pointed at one via
`CLAUDE_PROJECT_DIR`. The script deliberately falls back to its own location when that variable
names a tree with no hooks — that fallback is correct, it is what makes `hook-fire-log.sh
report` work from any directory — but it means setting the variable alone lands the report back
on the real repo's 13 live hooks, and the test would then assert against a full population while
claiming to exercise the empty one.
"""
_, env = sandbox
fake_scripts = tmp_path / "scripts"
fake_scripts.mkdir()
copied = fake_scripts / "hook-fire-log.sh"
copied.write_text(SINK.read_text())
copied.chmod(0o755)
runenv = dict(env)
runenv.pop("CLAUDE_PROJECT_DIR", None)
p = subprocess.run(
["bash", str(copied), "report", "--all", "--dir", str(tmp_path / "log")],
capture_output=True,
cwd=str(tmp_path),
env=runenv,
timeout=60,
)
assert p.returncode == 2, (
"the report exited 0 over an empty hook population. It must refuse rather than print a "
f"clean table of nothing. stdout={p.stdout.decode()!r}"
)
assert b"refusing to report" in p.stderr
# ------------------------------------------------------------------------------------------------
# PROOFS FOR THE ROUND-2 FIXES. Each of these went red before its fix and green after; each names
# the failure it pins, because "this test exists for a reason" is not a reason.
# ------------------------------------------------------------------------------------------------
def test_stderr_is_NOT_silenced(sandbox):
"""The worst defect this change shipped, and the cheapest to have missed.
`exec 0<"$sin" 2>/dev/null` reads as "suppress errors from this redirection". It is not: `exec`
with redirections and no command applies them to the shell PERMANENTLY, so it sent the HOOK'S
ENTIRE STDERR to /dev/null for the rest of its life. Every husky guard's user-facing output is
stderr — the H6 "push to main BLOCKED" message, the BOM guard's remediation text — so the guards
went on blocking while telling the human nothing about why.
Invisible to the original A/B, which compared only stdout and exit status.
"""
root, env = sandbox
hook = root / "noisy.sh"
hook.write_text(
"#!/usr/bin/env bash\nset -uo pipefail\n"
f'. "{SINK}"\n'
'etv_hook_fire_begin noisy "" stream || true\n'
"input=$(cat)\n"
'printf "IMPORTANT DIAGNOSTIC\\n" >&2\n'
"exit 1\n"
)
p = subprocess.run(
["bash", str(hook)], input=b'{"tool_name":"Bash"}', capture_output=True, cwd=str(root), env=env, timeout=60
)
assert p.returncode == 1
assert b"IMPORTANT DIAGNOSTIC" in p.stderr, f"the hook's stderr was swallowed by the instrumentation: {p.stderr!r}"
def test_output_SURVIVES_a_vanished_stdout_tempfile(sandbox):
"""The swallowed-`deny` path, found by cold review by stubbing `mktemp`.
Two coupled mistakes: the fd restore lived inside the same conditional as the replay, so a
missing file left stdout still pointing at the temp target; and the replay read the PATH, so an
unlinked-but-open file was unrecoverable even though its bytes existed. The hook here deletes
its own scratch after printing, which is what a $TMPDIR reaper does to it from outside.
"""
root, env = sandbox
hook = root / "vanish.sh"
hook.write_text(
"#!/usr/bin/env bash\nset -uo pipefail\n"
f'. "{SINK}"\n'
'etv_hook_fire_begin vanish "" capture || true\n'
"input=$(cat)\n"
r'printf "{\"hookSpecificOutput\":{\"permissionDecision\":\"deny\"}}"' + "\n"
'rm -f "${TMPDIR:-/tmp}"/etv-hook-stdout.* 2>/dev/null || true\n'
)
tmp = root / "vanish-tmp"
tmp.mkdir(exist_ok=True)
p = subprocess.run(
["bash", str(hook)],
input=b'{"tool_name":"Bash"}',
capture_output=True,
cwd=str(root),
env={**env, "TMPDIR": str(tmp)},
timeout=60,
)
assert p.returncode == 0
assert b'"permissionDecision":"deny"' in p.stdout, (
"the guard's deny was DISCARDED when its stdout scratch file vanished mid-run. The hook "
f"exited 0 with no output, which the harness reads as allow. stdout={p.stdout!r}"
)
@pytest.mark.parametrize(
"emit,code,expected",
[
# A NON-CANONICAL value is recorded as non-canonical, not laundered into a valid decision.
# This case went both ways before settling: first filed as unclassified prose, then
# lowercased into a clean `deny` (manufacturing a decision the harness may never honour).
(r"{\"permissionDecision\":\"Deny\"}", 0, "unrecognized"),
# A non-zero status neither ERASES a printed decision nor annotates it. The status has its
# own field; the decision field states the decision and nothing else.
(r"{\"permissionDecision\":\"deny\"}", 1, "deny"),
# A failure with nothing classifiable IS an error.
("", 1, "error"),
# Exit 2 is the harness's block channel and DOMINATES the printed JSON. Recording the
# printed `allow` would report a permit for a call that was actually refused — the one
# direction a log of security decisions must never be wrong in.
(r"{\"permissionDecision\":\"allow\"}", 2, "deny-exit2"),
],
)
def test_the_classifier_does_not_MISREPORT(sandbox, emit, code, expected):
root, env = sandbox
logdir = root / f"cls-{expected}-{code}"
runenv = {**env, "ETV_HOOK_FIRE_LOG_DIR": str(logdir)}
hook = root / f"cls-{expected}-{code}.sh"
hook.write_text(
"#!/usr/bin/env bash\nset -uo pipefail\n"
f'. "{SINK}"\n'
'etv_hook_fire_begin cls "" capture || true\n'
"input=$(cat)\n" + (f'printf "{emit}"\n' if emit else "") + f"exit {code}\n"
)
subprocess.run(
["bash", str(hook)],
input=b'{"session_id":"s1","tool_name":"Bash"}',
capture_output=True,
cwd=str(root),
env=runenv,
timeout=60,
)
rec = [ln for ln in (logdir / "s1.jsonl").read_text().splitlines() if '"phase":"exit"' in ln]
assert f'"decision":"{expected}"' in rec[0], f"expected {expected}, got {rec[0]}"
def test_the_word_additionalContext_in_PROSE_is_not_a_decision(sandbox):
"""`grep -q additionalContext` matched the bare word anywhere, including human text."""
root, env = sandbox
logdir = root / "cls-prose"
hook = root / "prose.sh"
hook.write_text(
"#!/usr/bin/env bash\nset -uo pipefail\n"
f'. "{SINK}"\n'
'etv_hook_fire_begin prose "" capture || true\n'
"input=$(cat)\n"
'printf "note: this hook does not use additionalContext at all\\n"\n'
)
subprocess.run(
["bash", str(hook)],
input=b'{"session_id":"s1","tool_name":"Bash"}',
capture_output=True,
cwd=str(root),
env={**env, "ETV_HOOK_FIRE_LOG_DIR": str(logdir)},
timeout=60,
)
rec = [ln for ln in (logdir / "s1.jsonl").read_text().splitlines() if '"phase":"exit"' in ln]
assert '"decision":"output"' in rec[0], f"prose was classified as a decision: {rec[0]}"
def test_the_session_id_cannot_ESCAPE_the_log_directory(sandbox, tmp_path):
"""The log FILENAME was built from an unscrubbed payload field while the log FIELD was scrubbed.
Unreachable with harness-generated UUIDs, fixed anyway: a file whose stated thesis is "restrict
the value space so there is no escaping bug to have" should not exempt the one use that becomes
a path.
"""
_root, env = sandbox
logdir = tmp_path / "logs"
hook = tmp_path / "esc.sh"
hook.write_text(
f'#!/usr/bin/env bash\nset -uo pipefail\n. "{SINK}"\netv_hook_fire_begin esc "" capture || true\ninput=$(cat)\n'
)
evil = '{"session_id":"../../escaped","tool_name":"Bash"}'
subprocess.run(
["bash", str(hook)],
input=evil.encode(),
capture_output=True,
cwd=str(tmp_path),
env={**env, "ETV_HOOK_FIRE_LOG_DIR": str(logdir)},
timeout=60,
)
written = list(logdir.glob("*.jsonl"))
assert written, "nothing was logged at all"
for f in written:
assert f.parent == logdir, f"a record escaped the log directory: {f}"
assert not (tmp_path / "escaped.jsonl").exists()
def test_the_suite_does_not_write_to_the_PRODUCTION_log(sandbox):
"""`conftest.py` must isolate every test, not just this file's.
Before it, running `pytest scripts/tests` put 115 synthetic fires into
`$HOME/.cache/ersatztv/hook-fire/` — 96 merge-consent including two `deny`s — so
`hook-fire-log.sh report` described the test suite while looking exactly like a record of real
sessions. That is the inference problem this change exists to abolish, one layer up.
"""
assert os.environ.get("ETV_HOOK_FIRE_LOG_DIR"), (
"ETV_HOOK_FIRE_LOG_DIR is not set for this test, so any hook it drives writes to the real "
"log. scripts/tests/conftest.py should be setting it for every test."
)
default = Path(os.path.expanduser("~/.cache/ersatztv/hook-fire"))
assert Path(os.environ["ETV_HOOK_FIRE_LOG_DIR"]).resolve() != default.resolve()
before = sorted(p.stat().st_mtime_ns for p in default.glob("*.jsonl")) if default.exists() else []
root, env = sandbox
hook = root / "prod-check.sh"
hook.write_text(
"#!/usr/bin/env bash\nset -uo pipefail\n"
f'. "{SINK}"\n'
'etv_hook_fire_begin prodcheck "" capture || true\n'
"input=$(cat)\n"
)
subprocess.run(
["bash", str(hook)],
input=b'{"session_id":"s1","tool_name":"Bash"}',
capture_output=True,
cwd=str(root),
env=env,
timeout=60,
)
after = sorted(p.stat().st_mtime_ns for p in default.glob("*.jsonl")) if default.exists() else []
assert before == after, "a test run modified the production hook-fire log"
def test_DELETING_the_replay_makes_the_differential_go_RED(sandbox, positives, tmp_path):
"""THE MUTATION PROOF FOR THE TRANSPARENCY CLAUSE.
The coverage clause has its own proof (`test_a_hook_that_LOSES_its_instrumentation_is_DETECTED`).
That one says nothing about whether the differential test is load-bearing, and the inventory row
claims BOTH. So: disarm the replay in an isolated copy of the sink, point a real hook at it, and
the same comparison the differential performs must fail. Without this, "the A/B would catch a
broken wrapper" is an argument, and this repo's record is that arguments of that shape have been
wrong repeatedly — including for this very file, whose A/B was 97% empty-vs-empty on arrival.
"""
root, env = sandbox
mutated = tmp_path / "hook-fire-log.sh"
text = SINK.read_text()
marker = ' cat "$ETV_HOOK_FIRE_STDOUT_TMP" 2>/dev/null || true'
assert marker in text, (
"the replay line has moved; this mutation no longer targets it. Retarget it rather than "
"loosening the match — a mutation that silently stops mutating proves nothing, which is "
"the whole failure class this file exists to catch."
)
mutated.write_text(text.replace(marker, " : # MUTATED: replay removed", 1))
hook = tmp_path / "victim.sh"
hook.write_text(
"#!/usr/bin/env bash\nset -uo pipefail\n"
f'. "{mutated}"\n'
'etv_hook_fire_begin victim "" capture || true\n'
"input=$(cat)\n"
r'printf "{\"hookSpecificOutput\":{\"permissionDecision\":\"deny\"}}"' + "\n"
)
p = subprocess.run(
["bash", str(hook)],
input=b'{"tool_name":"Bash"}',
capture_output=True,
cwd=str(root),
env={**env, "TMPDIR": str(tmp_path)},
timeout=60,
)
assert p.stdout == b"", (
f"the mutation did not actually disarm the replay, so this proof establishes nothing: stdout={p.stdout!r}"
)
def test_no_exec_in_the_sink_carries_a_STDERR_REDIRECT():
"""The rule that has now been broken twice, enforced instead of restated.
`exec` with redirections and no command applies them to the SHELL, permanently. `exec ... 2>/dev/null`
therefore silences the hook's whole stderr rather than suppressing an error from that one
redirection. It shipped once in the stdin replay (silencing every husky guard's user-facing
output), was fixed, and was then reintroduced eight lines below the comment forbidding it.
A grep is a weak detector in general; here the pattern is exact and the cost of missing it is a
guard that blocks while explaining nothing.
"""
offenders = [
f"{SINK.name}:{i}: {ln.strip()}"
for i, ln in enumerate(SINK.read_text().splitlines(), 1)
if re.match(r"\s*exec\s[^|&;#]*2>", ln) and not ln.lstrip().startswith("#")
]
assert not offenders, (
"these `exec` lines carry a stderr redirection, which applies to the whole shell and "
"silences the hook:\n " + "\n ".join(offenders)
)
def test_the_log_and_the_REPLAY_agree_when_the_hook_uses_fd_4(sandbox):
"""Classification and replay must read the same bytes.
They did not: the classifier read fd 4 while the replay preferred the file, so a hook that used
fd 4 for its own purposes replayed its `deny` correctly to the harness and filed it in the log
as `no-op` — the record contradicting the decision it exists to record.
"""
root, env = sandbox
logdir = root / "log-fd4"
hook = root / "fd4.sh"
hook.write_text(
"#!/usr/bin/env bash\nset -uo pipefail\n"
f'. "{SINK}"\n'
'etv_hook_fire_begin fd4 "" capture || true\n'
"input=$(cat)\n"
"exec 4</dev/null\n" # the hook takes fd 4 for itself
r'printf "{\"hookSpecificOutput\":{\"permissionDecision\":\"deny\"}}"' + "\n"
)
p = subprocess.run(
["bash", str(hook)],
input=b'{"session_id":"s1","tool_name":"Bash"}',
capture_output=True,
cwd=str(root),
env={**env, "ETV_HOOK_FIRE_LOG_DIR": str(logdir)},
timeout=60,
)
assert b'"permissionDecision":"deny"' in p.stdout, f"replay lost the decision: {p.stdout!r}"
exits = [r for r in (logdir / "s1.jsonl").read_text().splitlines() if '"phase":"exit"' in r]
assert '"decision":"deny"' in exits[0], f"the harness saw a deny but the log recorded something else: {exits[0]}"
def test_an_UNWRITABLE_log_file_is_still_stderr_transparent(sandbox, tmp_path):
"""Fail-open must be SILENT, not merely non-fatal.
`printf ... >> "$file" 2>/dev/null` looks like it suppresses a failure to open the log. It does
not: redirections apply left to right, so bash opens the file first and reports the failure on
the stderr still in force — the hook prints `Operation not permitted` straight at the harness.
`test_logging_failure_does_not_break_the_hook` could not see it because its path dies at `mkdir`
and never reaches an existing-but-unwritable destination.
"""
_root, env = sandbox
logdir = tmp_path / "ro-log"
logdir.mkdir()
victim = logdir / "s1.jsonl"
victim.write_text("")
victim.chmod(0o400)
hook = tmp_path / "ro.sh"
hook.write_text(
"#!/usr/bin/env bash\nset -uo pipefail\n"
f'. "{SINK}"\n'
'etv_hook_fire_begin ro "" capture || true\n'
"input=$(cat)\n"
r'printf "{\"hookSpecificOutput\":{\"permissionDecision\":\"deny\"}}"' + "\n"
)
p = subprocess.run(
["bash", str(hook)],
input=b'{"session_id":"s1","tool_name":"Bash"}',
capture_output=True,
cwd=str(tmp_path),
env={**env, "ETV_HOOK_FIRE_LOG_DIR": str(logdir)},
timeout=60,
)
assert p.returncode == 0
assert p.stdout == b'{"hookSpecificOutput":{"permissionDecision":"deny"}}'
assert p.stderr == b"", (
"an unwritable log leaked a diagnostic to the harness. Observability that cannot write must "
f"be silent, not chatty: {p.stderr!r}"
)
def test_NUL_bytes_in_hook_output_survive(sandbox):
"""A shell variable cannot hold a NUL, so replaying through `$(...)` silently drops them.
Pathological for a JSON decision, but the replay must be byte-exact for whatever the hook wrote,
and "it drops bytes only for content we do not expect" is the reasoning this file exists to
avoid. The common path streams the file; only the unlinked-file rescue is lossy, and that is
stated in the code.
"""
root, env = sandbox
hook = root / "nul.sh"
hook.write_text(
"#!/usr/bin/env bash\nset -uo pipefail\n"
f'. "{SINK}"\n'
'etv_hook_fire_begin nul "" capture || true\n'
"input=$(cat)\n"
r"printf 'a\000b\n'" + "\n"
)
p = subprocess.run(
["bash", str(hook)], input=b'{"tool_name":"Bash"}', capture_output=True, cwd=str(root), env=env, timeout=60
)
assert p.stdout == b"a\x00b\n", f"NUL-containing output was mangled: {p.stdout!r}"
assert b"null byte" not in p.stderr, f"a warning leaked to the harness: {p.stderr!r}"
@pytest.mark.parametrize(
"emit,code,expected",
[
# Every non-canonical value, not just the ones a restricted character class admits.
(r"{\"permissionDecision\":\"deny2\"}", 0, "unrecognized"),
(r"{\"permissionDecision\":\"deny_now\"}", 0, "unrecognized"),
# Unclassified output plus a FAILING exit is an error, not `output`: the report histograms
# the decision, so filing it as `output` hid the failure entirely.
("diagnostic text", 1, "error"),
],
)
def test_odd_values_and_failing_exits_are_not_LAUNDERED(sandbox, emit, code, expected):
root, env = sandbox
logdir = root / f"odd-{expected}-{abs(hash((emit, code))) % 9999}"
hook = root / f"odd-{abs(hash((emit, code))) % 9999}.sh"
hook.write_text(
"#!/usr/bin/env bash\nset -uo pipefail\n"
f'. "{SINK}"\n'
'etv_hook_fire_begin odd "" capture || true\n'
"input=$(cat)\n" + (f'printf "{emit}"\n' if emit else "") + f"exit {code}\n"
)
subprocess.run(
["bash", str(hook)],
input=b'{"session_id":"s1","tool_name":"Bash"}',
capture_output=True,
cwd=str(root),
env={**env, "ETV_HOOK_FIRE_LOG_DIR": str(logdir)},
timeout=60,
)
rec = [r for r in (logdir / "s1.jsonl").read_text().splitlines() if '"phase":"exit"' in r]
assert f'"decision":"{expected}"' in rec[0], f"expected {expected}, got {rec[0]}"
def test_an_INHERITED_flushed_flag_does_not_disable_reporting(sandbox):
"""`ETV_HOOK_FIRE_FLUSHED` was defaulted, never reset.
Exported by a parent — or set by an earlier `begin` in the same shell — a stale `1` made the
first flush return immediately: stdout stayed redirected and no exit record was written. Every
test assumed a clean environment, which is the assumption a hook running inside someone else's
process cannot make.
"""
root, env = sandbox
logdir = root / "log-inherited"
hook = root / "inherited.sh"
hook.write_text(
"#!/usr/bin/env bash\nset -uo pipefail\n"
f'. "{SINK}"\n'
'etv_hook_fire_begin inherited "" capture || true\n'
"input=$(cat)\n"
r'printf "{\"hookSpecificOutput\":{\"permissionDecision\":\"deny\"}}"' + "\n"
)
p = subprocess.run(
["bash", str(hook)],
input=b'{"session_id":"s1","tool_name":"Bash"}',
capture_output=True,
cwd=str(root),
env={**env, "ETV_HOOK_FIRE_LOG_DIR": str(logdir), "ETV_HOOK_FIRE_FLUSHED": "1"},
timeout=60,
)
assert p.stdout == b'{"hookSpecificOutput":{"permissionDecision":"deny"}}', (
f"an inherited FLUSHED=1 left stdout redirected and swallowed the decision: {p.stdout!r}"
)
exits = [r for r in (logdir / "s1.jsonl").read_text().splitlines() if '"phase":"exit"' in r]
assert exits and '"decision":"deny"' in exits[0], f"no exit record was written: {exits}"
@pytest.mark.parametrize("signame", ["TERM", "INT", "HUP"])
def test_a_SIGNALLED_hook_behaves_EXACTLY_as_an_uninstrumented_one(sandbox, signame):
"""The invariant that replaced the signal trap, asserted as an A/B rather than as a rescue.
A `trap ... TERM` was added so a killed hook would not lose already-printed output. It caused
three defects in three rounds, the last of which settles it: bash does not run a trap until the
current foreground command finishes, so an instrumented hook mid-`curl` took 30s to die where it
had taken 1s — a TERM-then-KILL supervisor then gets no flush at all AND a 29s stall. The rescue
was worth less than the transparency it cost.
So the contract is the same one the rest of this file asserts: under a signal, instrumented and
uninstrumented are indistinguishable. Both the STATUS and the TIME TO DIE are compared; the
latter is the one the trap broke, and no assertion on output could have caught it.
"""
import signal
import time
root, env = sandbox
sig = getattr(signal, f"SIG{signame}")
body = (
"input=$(cat)\n"
r'printf "{\"hookSpecificOutput\":{\"permissionDecision\":\"deny\"}}"' + "\n"
"sleep 25\n"
)
instrumented = root / f"sigab-{signame}.sh"
instrumented.write_text(
f'#!/usr/bin/env bash\nset -uo pipefail\n. "{SINK}"\netv_hook_fire_begin sigab "" stream || true\n' + body
)
control = root / f"sigab-control-{signame}.sh"
control.write_text("#!/usr/bin/env bash\nset -uo pipefail\n" + body)
results = {}
for tag, script in (("control", control), ("instrumented", instrumented)):
payload = root / f"sigab-{signame}-{tag}.json"
payload.write_bytes(b'{"session_id":"s1","tool_name":"Bash"}')
with open(payload, "rb") as fh:
# SIGNAL THE PROCESS GROUP, not the pid. A non-interactive bash defers a fatal signal
# until its foreground command finishes, trapped or not — so signalling the pid alone
# made BOTH sides take the full sleep and the timing assertion could not distinguish
# anything. Measured: pid-only gives control 4.0s and trapped 4.1s; group signalling
# gives control 0.002s and trapped 0.054s. A supervisor kills the group, so this is
# also the shape that actually occurs.
p = subprocess.Popen(
["bash", str(script)],
stdin=fh,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE,
cwd=str(root),
env=env,
start_new_session=True,
)
time.sleep(1.0)
t0 = time.monotonic()
os.killpg(os.getpgid(p.pid), sig)
out, err = p.communicate(timeout=40)
results[tag] = (p.returncode, time.monotonic() - t0, out, err)
(rc_a, dt_a, out_a, err_a), (rc_b, dt_b, out_b, err_b) = (
results["control"],
results["instrumented"],
)
assert out_a == out_b, f"SIG{signame}: stdout differs under signal: {out_a!r} vs {out_b!r}"
# ONE EXEMPTION, measured and narrow. On a group kill with a live foreground child, bash prints
# its own job-control notice (`Terminated: 15 sleep 5`). The instrumented hook does work in
# its EXIT handler and therefore lives ~50ms longer than the control, which dies before bash
# gets to print. Isolated: sourcing the sink alone does not produce it, and a no-op `EXIT` trap
# does not either — it is doing ANY work at exit that opens the window, which is the sink's
# whole purpose. Documented as a limit in `testing.hook-reports-its-own-execution` rather than
# papered over, and scoped to bash's exact notice so any other stderr difference still fails.
def strip_jobnotice(e: bytes) -> bytes:
# Two observed forms: bare (`Terminated: 15 sleep 5`) and attributed to whatever line of
# the sink was executing (`…/hook-fire-log.sh: line 109: 63769 Hangup: 1 sleep 5`). Both
# require one of bash's four signal words followed by `:` or whitespace, so an ordinary
# diagnostic still fails the comparison.
return b"\n".join(
ln for ln in e.split(b"\n") if not re.search(rb"(^|\s)(Terminated|Hangup|Interrupt|Killed)(:|\s|$)", ln)
)
assert strip_jobnotice(err_a) == strip_jobnotice(err_b), (
f"SIG{signame}: stderr differs under signal beyond bash's job-control notice: {err_a!r} vs {err_b!r}"
)
assert rc_a == rc_b, (
f"SIG{signame}: exit status differs, control={rc_a} instrumented={rc_b}. git and the "
"harness both read this status."
)
assert dt_b < dt_a + 2.0, (
f"SIG{signame}: the instrumented hook took {dt_b:.1f}s to die where the uninstrumented one "
f"took {dt_a:.1f}s. A trap handler does not run until the foreground command finishes, so "
"trapping the signal makes a killed hook hang for the length of whatever it was doing."
)
@pytest.mark.parametrize(
"locale_env",
[
{"LANG": "en_US.UTF-8"},
{"LC_CTYPE": "en_US.UTF-8"},
{"LC_CTYPE": "UTF-8"}, # macOS Terminal's default, and the case that broke the fix
{"LC_ALL": "en_US.UTF-8"},
],
)
def test_an_INVALID_UTF8_byte_in_a_decision_is_still_classified(tmp_path, locale_env):
"""`local LC_ALL=C` does not export, so the child `sed`/`tr` never saw it — the fix was INERT.
One 0xE9 byte in a `permissionDecisionReason` made the classifier print `illegal byte sequence`
at the harness and file a real `deny` as `output`, and made the payload block file the record
under `unknown-session` with empty event and tool — manufacturing the exact never-fired vacuity
#776 exists to abolish.
It read as fixed because this author's shell sets `LANG` alone. The locale matrix is
parametrised because a single ambient locale tests one row of it: with an inherited `LC_CTYPE`,
`LC_CTYPE` outranks the exported `LANG=C` and the symptom returns in full.
"""
name = next(iter(locale_env.values()))
have = subprocess.run(["locale", "-a"], capture_output=True, text=True).stdout.split()
if name not in have and name.replace("UTF-8", "utf8") not in have:
pytest.skip(
f"{name} is not installed here, so bash itself warns and the assertion would be "
"measuring the missing locale rather than the export fix. The hazard needs a real "
"non-C locale to exist."
)
logdir = tmp_path / "loclog"
hook = tmp_path / "loc.sh"
hook.write_text(
"#!/usr/bin/env bash\nset -uo pipefail\n"
f'. "{SINK}"\n'
'etv_hook_fire_begin loc "" capture || true\n'
"input=$(cat)\n"
'printf \'{"hookSpecificOutput":{"permissionDecision":"deny",'
'"permissionDecisionReason":"caf\\xe9"}}\'\n'
)
env = {"PATH": os.environ["PATH"], "HOME": os.environ["HOME"], "ETV_HOOK_FIRE_LOG_DIR": str(logdir), **locale_env}
p = subprocess.run(
["bash", str(hook)],
input=b'{"session_id":"s1","tool_name":"Bash"}',
capture_output=True,
cwd=str(tmp_path),
env=env,
timeout=60,
)
assert p.stderr == b"", f"{locale_env}: a locale diagnostic leaked to the harness: {p.stderr!r}"
record = (logdir / "s1.jsonl").read_text()
assert '"decision":"deny"' in record, f"{locale_env}: the decision was misfiled:\n{record}"
assert '"tool":"Bash"' in record, f"{locale_env}: identity fields were lost:\n{record}"
assert not (logdir / "unknown-session.jsonl").exists(), (
f"{locale_env}: the record filed under unknown-session, so this fire reads as never having "
"happened in the report"
)
def test_a_NESTED_identity_field_does_not_outrank_the_TOP_LEVEL_one(tmp_path):
"""A greedy `.*` takes the LAST match, and payloads are one long line.
Removing the 64 KB cap is what armed this: a nested `{"session_id":…,"tool_name":…}` inside a
`tool_response` began outranking the top-level identity, filing the whole invocation under the
wrong session — so the real session reads as never-fired. The cap had been accidentally
protecting the right answer, which is the kind of load a bound can be silently carrying.
"""
logdir = tmp_path / "nestlog"
hook = tmp_path / "nest.sh"
hook.write_text(
"#!/usr/bin/env bash\nset -uo pipefail\n"
f'. "{SINK}"\n'
'etv_hook_fire_begin nest "" capture || true\n'
"input=$(cat)\n"
)
import json as _json
payload = _json.dumps(
{
"session_id": "TOP-SESSION",
"hook_event_name": "PreToolUse",
"tool_name": "TopTool",
"tool_input": {"filler": "x" * 1000},
"tool_response": {"session_id": "NESTED-SESSION", "tool_name": "NestedTool"},
}
)
subprocess.run(
["bash", str(hook)],
input=payload.encode(),
capture_output=True,
cwd=str(tmp_path),
env={**os.environ, "ETV_HOOK_FIRE_LOG_DIR": str(logdir)},
timeout=60,
)
assert (logdir / "TOP-SESSION.jsonl").exists(), (
f"records filed under the wrong session: {[f.name for f in logdir.glob('*.jsonl')]}"
)
rec = (logdir / "TOP-SESSION.jsonl").read_text()
assert '"tool":"TopTool"' in rec, f"a nested tool_name outranked the top-level one:\n{rec}"
def test_a_PRESENT_but_empty_decision_is_not_laundered(sandbox):
"""`{"permissionDecision":""}` extracted as empty, which is indistinguishable from absent, so it
bypassed `unrecognized` and was filed as `output` — a malformed decision laundered into "the
hook just printed something"."""
root, env = sandbox
logdir = root / "log-empty-decision"
hook = root / "emptydec.sh"
hook.write_text(
"#!/usr/bin/env bash\nset -uo pipefail\n"
f'. "{SINK}"\n'
'etv_hook_fire_begin emptydec "" capture || true\n'
"input=$(cat)\n"
r'printf "{\"hookSpecificOutput\":{\"permissionDecision\":\"\"}}"' + "\n"
)
subprocess.run(
["bash", str(hook)],
input=b'{"session_id":"s1","tool_name":"Bash"}',
capture_output=True,
cwd=str(root),
env={**env, "ETV_HOOK_FIRE_LOG_DIR": str(logdir)},
timeout=60,
)
rec = [r for r in (logdir / "s1.jsonl").read_text().splitlines() if '"phase":"exit"' in r]
assert '"decision":"unrecognized"' in rec[0], f"an empty decision was laundered: {rec[0]}"
def test_identity_fields_BEYOND_the_fast_path_cap_are_still_found(tmp_path):
"""The bound must be an optimisation, never a correctness dependency.
A plain 256 KB cap reintroduced the exact defect the unbounded read had just fixed: a payload
whose filler pushes `session_id` past the cap returns nothing, the record files under
`unknown-session`, and that fire reads as NEVER HAVING HAPPENED in the report. The nested-field
test could not see it — its identities sit before only 1,000 bytes of filler.
So the cap is a fast path with an unbounded fallback, and this test puts the identity where only
the fallback can reach it.
"""
import json as _json
hook = tmp_path / "big.sh"
hook.write_text(
f'#!/usr/bin/env bash\nset -uo pipefail\n. "{SINK}"\netv_hook_fire_begin big "" capture || true\ninput=$(cat)\n'
)
logdir = tmp_path / "biglog"
payload = _json.dumps(
{
"tool_input": {"filler": "x" * 400_000},
"session_id": "TOP-SESSION",
"hook_event_name": "PreToolUse",
"tool_name": "TopTool",
}
)
subprocess.run(
["bash", str(hook)],
input=payload.encode(),
capture_output=True,
cwd=str(tmp_path),
env={**os.environ, "ETV_HOOK_FIRE_LOG_DIR": str(logdir)},
timeout=90,
)
assert (logdir / "TOP-SESSION.jsonl").exists(), (
"identity beyond the fast-path cap was not found, so the fire filed under "
f"{[f.name for f in logdir.glob('*.jsonl')]} and reads as never having happened"
)
rec = (logdir / "TOP-SESSION.jsonl").read_text()
assert '"tool":"TopTool"' in rec and '"event":"PreToolUse"' in rec, rec
def test_the_field_helper_does_not_LEAK_into_the_hooks_namespace(sandbox):
"""A bash function defined inside another function is still GLOBAL.
A short generic name (`_etv_field`) therefore survives `begin` and can collide with, or
overwrite, a function the hook itself defines — and it would refer to a now-unset variable.
"""
root, env = sandbox
hook = root / "ns.sh"
hook.write_text(
"#!/usr/bin/env bash\nset -uo pipefail\n"
f'. "{SINK}"\n'
'etv_hook_fire_begin ns "" capture || true\n'
"input=$(cat)\n"
"if declare -F _etv_field >/dev/null 2>&1; then echo LEAKED_etv_field; fi\n"
"if declare -F etv_hook_fire__field >/dev/null 2>&1; then echo LEAKED_namespaced; fi\n"
"echo CLEAN\n"
)
p = subprocess.run(
["bash", str(hook)],
input=b'{"session_id":"s1","tool_name":"Bash"}',
capture_output=True,
cwd=str(root),
env=env,
timeout=60,
)
assert b"LEAKED" not in p.stdout, f"a helper leaked into the hook's namespace: {p.stdout!r}"
assert b"CLEAN" in p.stdout