script/lint runs the linter directly when it is already inside a
container and otherwise builds Dockerfile.lint, so the linter never runs
on a developer host. That closes three host-only mechanisms: the result
cache golangci-lint keys on file content rather than location, which
produced a confirmed false green and findings reported against other
checkouts; the host-global $TMPDIR/golangci-lint.lock, which fails a run
in a way no caller can distinguish from findings; and host/container
version skew, which hid thirteen findings on one repo.
Detection is on LINT_IN_CONTAINER=1, set by every Dockerfile, and on
nothing else. The two directions are not symmetric: a false negative
inside a container attempts a nested docker build, finds no daemon and
fails loudly, while a false positive on a host silently lints there,
which is the defect this issue exists to kill. /.dockerenv is therefore
rejected even as a fallback -- measured absent inside BuildKit RUN steps
and present on any host that is itself a container, so it fails in both
directions and one of them is the dangerous one.
Nothing else changes shape. The Dockerfile still runs make check,
script/check still runs test, lint and fmt-check, script/cibuild is
still a single docker build with CHECK_EPOCH and VERSION, and the Go
multistage lint stage and its COPY --from=lint ordering dependency
survive with ENV LINT_IN_CONTAINER=1 added. Dockerfile.lint is the
standalone developer-host path and carries the same CHECK_EPOCH guard,
with the ARG below the dependency layer so only the lint re-runs.
The script/bootstrap golangci-lint install and the per-checkout
GOLANGCI_LINT_CACHE/TMPDIR wrapper are deleted as superseded. Neither
has a caller left. A JS repo's yarn install stays: the rule is that no
lint verdict may come from a host invocation, not that no linter binary
may exist there, and in a repo whose formatter is its linter the
formatter necessarily runs on the host.
golangci-lint config verify is kept, on measurement. Under the pinned
v2.12.2 a bogus top-level key and a bogus key under linters.settings.lll
both pass `golangci-lint run` with exit 0 and `0 issues` while config
verify exits 3 and names them; an unknown linter name fails run and
passes config verify. It needs no network: every case reproduced
byte-identically under `docker run --network none`, in a container where
`getent hosts golangci-lint.run` exits 2.
Comment blocks were cut hard across every file this unit touches.
.dockerignore drops from 67 comment lines to 28, script/cibuild from 17
to 12, script/docker from 18 to 12, and prompts/REPO_POLICIES.md from
1182 lines to 907. What remains says why a line is load-bearing; the
discovery narratives are gone.
script/cibuild was a plain `docker build .`, and the Dockerfile does
`COPY . .` followed by `RUN make check`. Docker invalidates a COPY layer
only when the copied content changes, so on an unchanged tree the check
layer was served from cache, the suite never ran, and the build still
exited 0. Measured here: run 1 took 18.5s and ran the suite; run 2 on a
byte-identical tree took 0.286s with `RUN make check` CACHED.
script/cibuild and script/docker now assign a per-invocation nonce on its
own line and pass it as --build-arg CHECK_EPOCH. The Dockerfile declares
ARG CHECK_EPOCH, guards it with `[ -n "$CHECK_EPOCH" ] || exit 1`, and
expands it into the check command. Post-fix, two consecutive runs both
execute make check (17.4s / 8.1s) with `RUN script/bootstrap` still
CACHED, so dependency layers are untouched and the build ceiling is not
at risk.
The guard is what makes a bare `docker build .` — the command
REPO_POLICIES named verbatim — fail closed rather than reuse the empty
and therefore stable cache key; verified failing in 0.455s. Holding the
epoch constant restores the false green (run 2 fully CACHED), which pins
the varying value as the operative mechanism rather than a coincidence.
Because the guard references $CHECK_EPOCH it is itself value-keyed:
BuildKit renders the epoch into that layer's description and re-runs the
layer when the value changes. Each stage therefore has two independent
invalidation points, the guard and the expansion, and the guard always
precedes the check RUN. Both are kept and the prose now records this;
the expansion remains defence in depth and is what puts the epoch in the
build log.
The false guarantee was org-canonical text in more than one document, so
it is corrected everywhere it appeared rather than only where the issue
first found it. REPO_POLICIES.md carried it in two places, and its Go
multistage template had check steps in two stages; ARG is stage-scoped,
so both stages get the treatment or the fleet inherits the half-fixed
shape. CODE_STYLEGUIDE_GO.md restated the guarantee for the bare command
this change makes fail closed. NEW_REPO_CHECKLIST.md specified the
pre-fix script/cibuild verbatim, so every new repo would have been born
with the false green, and EXISTING_REPO_CHECKLIST.md ended on a
`docker build` acceptance item that the guard makes unsatisfiable by
design — an agent working that checklist would have been led to delete
the guard to tick the last box. Both checklists' Dockerfile criteria were
also satisfiable by a Dockerfile whose check layers are still frozen, and
now require the ARG and guard in every check-running stage.
REPO_POLICIES.md's own Dockerfile criterion carried that same incomplete
form; it is tightened by cross-reference to the CHECK_EPOCH rule rather
than by duplicating the canonical block. The Go template's Key points
gain a caveat that the cache-bust turns the `COPY --from=lint` no-op into
a content-cache hit, so a repo using a file-dependency trick for stage
ordering must re-prove that ordering on a warm cache after adopting it.
That was re-proved in another repo in the org which uses the trick with a
marker file, where the ordering held; the caveat states explicitly that
it was not verified here, this repo being single-stage with no lint stage
to order against.
Add .gitignore, LICENSE (MIT), Makefile, Dockerfile, .dockerignore,
and pin prettier via yarn lockfile for integrity-checked markdown
formatting. Update REPO_POLICIES.md self-reference to point to this
repo. Format markdown files with prettier.
