fix: resume stranded merge-door publishes

.github/workflows/release.yml

@@ -205,31 +205,40 @@ jobs:
           fi
           changelog_section CHANGELOG.md "$VER" > "$RUNNER_TEMP/notes.md"
           cat "$RUNNER_TEMP/notes.md"
-      - name: nothing may exist yet — no tag, no release (re-runs refuse loudly)
+      - name: preflight — resume this merge, refuse every other collision
+        id: preflight
         if: steps.decide.outputs.ceremony == 'yes'
         env:
           GH_TOKEN: ${{ github.token }}
           VER: ${{ steps.facts.outputs.ver }}
-        # What makes a re-run of a completed ceremony refuse instead of
-        # clobber, and what catches a manual tag racing the merge.
+          MERGE_SHA: ${{ github.sha }}
+        # The pure table in lib/preflight.sh distinguishes a stranded run of
+        # this door from a completed release or a tag at another commit (#273).
         run: |
-          if git ls-remote --exit-code origin "refs/tags/$VER" >/dev/null 2>&1; then
-            echo "tag '$VER' already exists — this release already happened, or a manual tag won the race; refusing to re-release, creating nothing." >&2
-            exit 1
-          fi
+          tag_read_rc=0
+          tag_refs="$(git ls-remote --exit-code origin "refs/tags/$VER" "refs/tags/$VER^{}")" || tag_read_rc=$?
+          case "$tag_read_rc" in
+            0) tag_shas="$(printf '%s\n' "$tag_refs" | awk 'NF { print $1 }')" ;;
+            2) tag_shas="" ;;
+            *)
+              echo "could not read tag '$VER' from origin (git ls-remote exit $tag_read_rc) — refusing rather than assuming it does not exist." >&2
+              exit 1
+              ;;
+          esac
           # shellcheck source=/dev/null
           . "$CEREMONY_DIR/lib/forge.sh"
           forge_select ""
-          if ! exists="$(forge_release_exists "$VER")"; then
+          if ! released="$(forge_release_exists "$VER")"; then
             echo "could not read whether release '$VER' exists — refusing rather than assuming it does not (#191)." >&2
             exit 1
           fi
-          if [ "$exists" = yes ]; then
-            echo "release '$VER' already exists — refusing to re-release, creating nothing." >&2
-            exit 1
-          fi
+          # shellcheck source=/dev/null
+          . "$CEREMONY_DIR/lib/preflight.sh"
+          out="$(TAG_SHAS="$tag_shas" RELEASED="$released" release_preflight)"
+          printf '%s\n' "$out"
+          printf '%s\n' "$out" | grep '^resume=' >> "$GITHUB_OUTPUT"
       - name: tag the merge commit — same job as the publish, on purpose
-        if: steps.decide.outputs.ceremony == 'yes'
+        if: steps.decide.outputs.ceremony == 'yes' && steps.preflight.outputs.resume != 'yes'
         env:
           GH_TOKEN: ${{ github.token }}
           VER: ${{ steps.facts.outputs.ver }}

test/forge-backends.test.sh

@@ -1185,6 +1185,66 @@ release_read 200 '{"id":41,"tag_name":"1.2.3","draft":false}'
 forge_release_create 1.2.3 1.2.3 "$TMP/notes.md" >/dev/null 2>&1
 check "a published same-tag release is never deleted" 1 "" grep -q '^DELETE ' "$WRITES"
 
+# The merge door's preflight step is extracted and executed. Its network
+# edges are stubbed at the boundary, while the real pure decision library
+# consumes the gathered facts (#273).
+MERGE_PREFLIGHT="$TMP/merge-preflight.sh"
+{
+  printf '%s\n' '#!/usr/bin/env bash' 'set -e'
+  yq -r '.jobs.release-on-merge.steps[] | select(.id == "preflight") | .run' \
+    "$ROOT/.github/workflows/release.yml"
+} >"$MERGE_PREFLIGHT"
+chmod +x "$MERGE_PREFLIGHT"
+
+mkdir -p "$TMP/merge-preflight-lib/lib" "$TMP/merge-preflight-bin"
+ln -s "$ROOT/lib/preflight.sh" "$TMP/merge-preflight-lib/lib/preflight.sh"
+# shellcheck disable=SC2016 # expanded when the generated helper runs
+printf '%s\n' \
+  'forge_select() { :; }' \
+  'forge_release_exists() { case "$RELEASE_EXISTS" in error) return 1 ;; *) echo "$RELEASE_EXISTS" ;; esac; }' \
+  >"$TMP/merge-preflight-lib/lib/forge.sh"
+# shellcheck disable=SC2016 # expanded when the PATH stub is executed
+printf '%s\n' \
+  '#!/usr/bin/env bash' \
+  'case "$GIT_LS_REMOTE" in' \
+  '  absent) exit 2 ;;' \
+  '  error) exit 128 ;;' \
+  '  *) printf "%s\n" "$GIT_LS_REMOTE" ;;' \
+  'esac' >"$TMP/merge-preflight-bin/git"
+chmod +x "$TMP/merge-preflight-bin/git"
+
+merge_preflight_extracted() { [ "$(wc -l <"$MERGE_PREFLIGHT")" -ge 8 ]; }
+run_merge_preflight() {
+  : >"$TMP/merge-preflight-output"
+  CEREMONY_DIR="$TMP/merge-preflight-lib" \
+    GITHUB_OUTPUT="$TMP/merge-preflight-output" \
+    PATH="$TMP/merge-preflight-bin:$PATH" \
+    VER=1.2.3 MERGE_SHA=1111111111111111111111111111111111111111 \
+    RELEASE_EXISTS="$1" GIT_LS_REMOTE="$2" "$MERGE_PREFLIGHT"
+}
+merge_preflight_output_is() {
+  run_merge_preflight "$1" "$2" >/dev/null && \
+    [ "$(cat "$TMP/merge-preflight-output")" = "$3" ]
+}
+
+check "the merge door's preflight is extracted" 0 "" merge_preflight_extracted
+check "the merge door refuses an unreadable release state" 1 \
+  "refusing rather than assuming" run_merge_preflight error absent
+check "the merge door refuses an unreadable tag state" 1 \
+  "could not read tag '1.2.3'" run_merge_preflight no error
+check "ls-remote exit 2 is tag absence and proceeds" 0 "" \
+  merge_preflight_output_is no absent resume=no
+check "a matching peeled ref records a resume" 0 "" \
+  merge_preflight_output_is no \
+  $'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\trefs/tags/1.2.3\n1111111111111111111111111111111111111111\trefs/tags/1.2.3^{}' \
+  resume=yes
+tag_step_uses_preflight() {
+  yq -r '.jobs.release-on-merge.steps[] | select(.name | test("tag the merge commit")) | .if' \
+    "$ROOT/.github/workflows/release.yml" | grep -q 'steps.preflight.outputs.resume'
+}
+check "the merge-door tag step is conditioned on the preflight output" 0 "" \
+  tag_step_uses_preflight
+
 # The tag door's published-release guard is extracted and executed, like the
 # other workflow-shell contracts in this repository. The tag itself is this
 # door's premise, so only a published release refuses; adding the merge door's