ceremony-ci-probe/actions/labels-scope/labels-scope.sh
cluade-reviewer-andresmgsl 7d52b2cd4a feat(forge): refuse loudly when the client cannot speak the forge
The preflight half of #188, landed first so it stands alone: the forge is
decided once, before any sweep, and a client that cannot speak it exits
non-zero with a named reason.

Measured against forgejo.heavyduty.builders at 84bb1a4 — two of the three
actions reported SUCCESS having read nothing:

  labels-scope         exit 0  "no .github/labeler.yml" (the file is HTTP 200)
  labels-reconcile     exit 0  "reconciled."            (zero PRs enumerated)
  issueflow-reconcile  exit 1  "unexpected end of JSON input"

labels-reconcile's blind-sweep warning (#96) could not fire: it counts
unreadable PRs against a list `gh pr list` never produced, and a process
substitution's failure does not trip set -e, so total stayed 0. Installing
gh makes it worse, silencing the one loud failure.

Detection is measured, not inferred from docs: a real forgejo-runner v6.3.1
job (probe task 278) shows Forgejo populating the whole GITHUB_* namespace,
so GITHUB_ACTIONS proves nothing. GITHUB_API_URL's shape, GITEA_ACTIONS and
GITHUB_SERVER_URL do. The same probe shows the runner image carries neither
gh nor stoke, which is what makes the forgejo backend REST.

Tests declare CEREMONY_FORGE at the forge boundary rather than stubbing gh
and staying silent about the forge — the boundary move term 5 asks for.

Refs #188
2026-08-02 18:29:08 +00:00

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#!/usr/bin/env bash
if [ "${BASH_SOURCE[0]}" = "$0" ]; then
set -euo pipefail
else
# Fixture tests source the pure functions and deliberately inspect failures.
set -u
fi
# shellcheck source=lib/forge.sh
. "$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)/../../lib/forge.sh"
# labels-scope.sh — the additive half of the labels automation: derive
# scope:* labels from a PR's changed paths and ADD them, touching nothing
# else. This seat belonged to actions/labeler@v5 until #130: even under
# `sync-labels: false`, labeler computes (labels-fetched-at-job-start
# derived) and writes it back with `PUT /issues/{n}/labels`
# (src/labeler.ts: api.setLabels — a full replace), so any label applied
# between its read and its write is silently removed. On ceremony#128 the
# builder's `release` — the merge door's declared-intent read — landed in
# that window and vanished two seconds later; v6 and v7 write the same
# way, so the fix is this replacement, not a newer pin.
#
# The only write here is `POST /issues/{n}/labels`: GitHub adds the named
# labels, ignores ones already present, and removes nothing. A label
# applied while this runs survives by construction.
#
# The path mapping stays in the consumer's .github/labeler.yml, read via
# the API at CONFIG_REF — the base branch, never the PR head, so a PR
# cannot label itself by editing the mapping. The accepted shape is the
# one every governed repo uses:
#
# scope:name:
# - changed-files:
# - any-glob-to-any-file: ["glob", ...]
#
# in any YAML spelling (block or flow; a glob list may be a single
# string). Anything else — all-globs-to-all-files, branch matchers,
# negations, backslash escapes — is refused loudly rather than
# half-honoured: this parser exists to make one write additive, not to
# reimplement minimatch. Globs support `**` (crosses `/`), `*` and `?`
# (do not); a leading dot is not special; the whole path must match
# (`README` matches README, never docs/README).
log() { printf 'labels-scope: %s\n' "$*"; }
run() { # every mutation goes through here — DRY_RUN=1 logs instead of doing
if [ -n "${DRY_RUN:-}" ]; then log "DRY_RUN: $*"; else "$@"; fi
}
glob_to_regex() { # $1 = glob (the subset above) → anchored ERE, one line
local glob="$1" out="" c i=0 n
n="${#glob}"
while [ "$i" -lt "$n" ]; do
c="${glob:i:1}"
case "$c" in
\*)
if [ "${glob:i:2}" = '**' ]; then
out="$out.*"
i=$((i + 2))
continue
fi
out="${out}[^/]*"
;;
\?) out="${out}[^/]" ;;
[a-zA-Z0-9_/-]) out="$out$c" ;;
*) out="$out\\$c" ;; # every other byte is literal — ., +, {, (, …
esac
i=$((i + 1))
done
printf '^%s$\n' "$out"
}
parse_labeler_config() { # labeler.yml on stdin → "label<TAB>glob" lines
# yq only normalizes YAML to JSON; the shape contract is enforced in jq,
# where an unsupported key is a loud error naming the label it sits under.
yq -o=json '.' - | jq -r '
if type != "object" then
error("labeler config: top level must be a map of label -> rules")
else . end
| to_entries[]
| .key as $label
| (if (.value | type) != "array" then
error("labeler config: \($label): rules must be a list")
else .value end)[]
| (if type != "object" then
error("labeler config: \($label): each rule must be a map")
else . end)
| ((keys - ["changed-files"]) as $extra
| if ($extra | length) > 0 then
error("labeler config: \($label): unsupported key(s) \($extra | join(", ")) — the scope job accepts changed-files/any-glob-to-any-file only (#130)")
else . end)
| .["changed-files"]
| (if type == "object" then [.]
elif type == "array" then .
else error("labeler config: \($label): changed-files must be a list") end)[]
| (if type != "object" then
error("labeler config: \($label): each changed-files entry must be a map")
else . end)
| ((keys - ["any-glob-to-any-file"]) as $extra
| if ($extra | length) > 0 then
error("labeler config: \($label): unsupported matcher(s) \($extra | join(", ")) — the scope job accepts any-glob-to-any-file only (#130)")
else . end)
| .["any-glob-to-any-file"]
| (if type == "string" then [.]
elif type == "array" then .
else error("labeler config: \($label): any-glob-to-any-file must be a glob or a list of globs") end)[]
| (if type != "string" then
error("labeler config: \($label): globs must be strings")
elif contains("\\") then
error("labeler config: \($label): backslash in glob \(.) — escapes are not supported (#130)")
else . end)
| [$label, .] | @tsv
'
}
derive_labels() { # $1 = "label<TAB>glob" lines, $2 = changed files (one per
# line) → matched labels, one per line, config order, deduped
local tsv="$1" files="$2" label glob matched=$'\n'
[ -n "$files" ] || return 0
while IFS=$'\t' read -r label glob; do
[ -n "$label" ] || continue
case "$matched" in *$'\n'"$label"$'\n'*) continue ;; esac
if printf '%s\n' "$files" | grep -qE -- "$(glob_to_regex "$glob")"; then
matched="$matched$label"$'\n'
printf '%s\n' "$label"
fi
done <<<"$tsv"
}
main() {
# See labels-reconcile's twin (#188). This action's degraded read was the
# quietest of the three: an unreadable mapping and an absent one produced
# the same "nothing to derive" no-op, so on Forgejo a PR simply got no
# scope labels and nothing said why.
CEREMONY_FORGE_CLIENT="${CEREMONY_FORGE_CLIENT:-gh}" forge_preflight || return 1
REPO="${REPO:?set REPO to owner/name}"
PR_NUMBER="${PR_NUMBER:?set PR_NUMBER to the pull request number}"
CONFIG_REF="${CONFIG_REF:?set CONFIG_REF to the base commit the mapping is read at}"
CONFIG_PATH="${CONFIG_PATH:-.github/labeler.yml}"
local config tsv files labels
# No mapping is a consumer that has not adopted scope labels — an
# advisory no-op, not a red run (scopes locate, they do not alert). A
# mapping that EXISTS but does not parse still fails loudly below.
if ! config="$(gh api "repos/$REPO/contents/$CONFIG_PATH?ref=$CONFIG_REF" \
--jq '.content' 2>/dev/null | base64 -d)" || [ -z "$config" ]; then
log "no $CONFIG_PATH at $CONFIG_REF — nothing to derive"
return 0
fi
tsv="$(parse_labeler_config <<<"$config")"
files="$(gh api --paginate "repos/$REPO/pulls/$PR_NUMBER/files" --jq '.[].filename')"
labels="$(derive_labels "$tsv" "$files")"
if [ -z "$labels" ]; then
log "#$PR_NUMBER: no scope labels derived"
return 0
fi
local args=()
while IFS= read -r label; do args+=(-f "labels[]=$label"); done <<<"$labels"
run gh api "repos/$REPO/issues/$PR_NUMBER/labels" "${args[@]}" --silent
log "#$PR_NUMBER: scopes -> $(paste -sd, <<<"$labels") (additive POST; already-present names are no-ops)"
}
# sourced by test/labels-scope.test.sh for the fixture tests; executed in CI
if [ "${BASH_SOURCE[0]}" = "$0" ]; then
main "$@"
fi