test(ci): scope the precondition assertion to its step

Author: zfarrell

tests/workflow-lint-test.sh

@@ -165,11 +165,27 @@ check_permission "/pulls/" pull-requests "the PR reads"
 # A missing context script has to fail loudly somewhere, and it cannot be the context step: that
 # one is continue-on-error, so `bash <missing file>` exits 127 into a green run. The prompt
 # document gets this for free -- `cat` on a missing file fails its step -- and the script needs an
-# explicit check to match. It must sit in a step without continue-on-error, or it proves nothing.
-if ! grep -q "gather-review-context.sh is missing\|! -f \"\$script\"" "$WORKFLOW_FILE"; then
-  echo "FAIL nothing in $WORKFLOW_FILE checks that the context script arrived from the"
-  echo "     cross-repo checkout. A bad sparse-checkout pattern would exit 127 inside a"
-  echo "     continue-on-error step and leave the run green with an empty context."
+# explicit check to match.
+#
+# Scoped to the step, not grepped over the file, because where the check sits is the whole property
+# being asserted: the same `-f` test moved into the context step would satisfy a file-wide grep and
+# prove nothing. So pull the one step and require both halves -- that it tests for the script, and
+# that it is not continue-on-error.
+precondition_step=$(awk '/^      - name: Verify the context step.s preconditions$/ { found = 1; next }
+                         found && /^      - / { exit }
+                         found { print }' "$WORKFLOW_FILE")
+if [ -z "$precondition_step" ]; then
+  echo "FAIL no 'Verify the context step's preconditions' step in $WORKFLOW_FILE; a missing"
+  echo "     context script would exit 127 inside a continue-on-error step and leave the run"
+  echo "     green with an empty context"
+  failures=$((failures + 1))
+elif ! printf '%s\n' "$precondition_step" | grep -q -- '-f .*gather-review-context\.sh\|script=.*gather-review-context\.sh'; then
+  echo "FAIL the precondition step does not test for the context script:"
+  printf '%s\n' "$precondition_step" | sed 's/^/       /'
+  failures=$((failures + 1))
+elif printf '%s\n' "$precondition_step" | grep -q 'continue-on-error'; then
+  echo "FAIL the precondition step is continue-on-error, so the check it makes cannot fail the"
+  echo "     job and proves nothing"
   failures=$((failures + 1))
 else
   echo "ok   a missing context script fails the job rather than emptying the context"