fix: guard tag release publication

.github/workflows/release.yml

@@ -363,6 +363,22 @@ jobs:
           fi
           changelog_section CHANGELOG.md "$VER" > "$RUNNER_TEMP/notes.md"
           cat "$RUNNER_TEMP/notes.md"
+      - name: no published release may exist
+        env:
+          GH_TOKEN: ${{ github.token }}
+          VER: ${{ steps.assert.outputs.ver }}
+        run: |
+          # shellcheck source=/dev/null
+          . "$CEREMONY_DIR/lib/forge.sh"
+          forge_select ""
+          if ! exists="$(forge_release_exists "$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
       - name: artifact hook — the consumer's own release-artifact action
         # After the tag exists (it fired this door), before the publish —
         # the same contract as the merge door's twin step.

test/forge-backends.test.sh

@@ -1185,6 +1185,36 @@ 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 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
+# ls-remote half here would destroy the documented delete-and-re-push recovery.
+TAG_GUARD="$TMP/tag-release-guard.sh"
+{
+  printf '%s\n' '#!/usr/bin/env bash' 'set -e'
+  yq -r '.jobs.release-on-tag.steps[] | select(.name == "no published release may exist") | .run' \
+    "$ROOT/.github/workflows/release.yml"
+} >"$TAG_GUARD"
+chmod +x "$TAG_GUARD"
+mkdir -p "$TMP/tag-guard-lib/lib"
+printf '%s\n' \
+  'forge_select() { :; }' \
+  'forge_release_exists() { case "$RELEASE_EXISTS" in error) return 1 ;; *) echo "$RELEASE_EXISTS" ;; esac; }' \
+  >"$TMP/tag-guard-lib/lib/forge.sh"
+
+tag_guard_extracted() { [ "$(wc -l <"$TAG_GUARD")" -ge 8 ]; }
+run_tag_guard() {
+  CEREMONY_DIR="$TMP/tag-guard-lib" VER=1.2.3 RELEASE_EXISTS="$1" "$TAG_GUARD"
+}
+tag_door_has_no_tag_exists_guard() {
+  ! yq -r '.jobs.release-on-tag.steps[].run // ""' "$ROOT/.github/workflows/release.yml" | grep -q 'ls-remote'
+}
+check "the tag door's published-release guard is extracted" 0 "" tag_guard_extracted
+check "the tag door refuses an existing published release" 1 "release '1.2.3' already exists" run_tag_guard yes
+check "the tag door proceeds when no published release exists" 0 "" run_tag_guard no
+check "the tag door refuses when release state is unreadable" 1 "refusing rather than assuming" run_tag_guard error
+check "the tag door carries no tag-exists guard" 0 "" tag_door_has_no_tag_exists_guard
+
 # --- the github twins address their own paths ----------------------------
 . "$ROOT/lib/forge-github.sh"
 GITHUB_REPOSITORY=o/r