From e050bfe80ec8fca52b11b72c615ddf1108e0a676 Mon Sep 17 00:00:00 2001
From: Stefan Steiner <ssteiner@tableau.com>
Date: Tue, 26 May 2026 23:49:43 -0700
Subject: [PATCH] fix(ci): defer fromJson(release.outputs.pr) into a run block
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The follow-up steps added in PR #50 reference
`fromJson(steps.release.outputs.pr).headBranchName` directly in `ref:`
(checkout) and `env:` (push) blocks. GitHub Actions evaluates every
`${{ }}` expression in the workflow at job-load time, BEFORE per-step
`if:` gates short-circuit. When release-please runs on a push that
doesn't produce a release PR (e.g. a PR merge whose conventional-
commit was already covered by an earlier release), `pr` is the empty
string, `fromJson('')` errors out, and the entire job fails with:

  ##[error]The template is not valid. .../release-please.yml
  (Line: 203, Col: 19): Error reading JToken from JsonReader.
  Path '', line 0, position 0.

This blocks release-please from ever opening the next release PR.
Observed in run 26494686197 on the merge of PR #50 itself.

Fix: extract the branch name in a new "Resolve release-please branch
name" step (id=`branch`) that does the parse via `jq` inside a `run:`
block — that block only runs when the step's `if:` gate passes, so
the parse is never attempted on empty input. The downstream
`actions/checkout` `ref:` and the final `git push` `env: BRANCH:`
both reference `steps.branch.outputs.name`, which evaluates safely
to the empty string when the step was skipped.

Add a doc comment explaining the GHA expression-evaluation timing
trap so the next person reading the workflow doesn't accidentally
re-introduce the same pattern.
---
 .github/workflows/release-please.yml | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/release-please.yml b/.github/workflows/release-please.yml
index cbf280d..8f0488a 100644
--- a/.github/workflows/release-please.yml
+++ b/.github/workflows/release-please.yml
@@ -79,11 +79,35 @@ jobs:
       # exclusion is the safety net that protects the released
       # binary even if a maintainer merges in a tiny window between
       # release-please's force-push and our follow-up step landing.
+      # Extract the release-please branch name into its own step
+      # output. We can't reference `fromJson(steps.release.outputs.pr)`
+      # directly in `ref:` / `env:` further down, because GitHub
+      # Actions evaluates every `${{ }}` expression in the workflow
+      # at job-load time — even on steps gated by `if:` that won't
+      # run. When `pr` is empty (no release PR this run),
+      # `fromJson('')` errors with "Error reading JToken from
+      # JsonReader." Wrapping the parse in a `run:` block keeps it
+      # inside the `if`-gate.
+      - name: Resolve release-please branch name
+        id: branch
+        if: ${{ steps.release.outputs.pr != '' }}
+        env:
+          PR_JSON: ${{ steps.release.outputs.pr }}
+        run: |
+          set -euo pipefail
+          BRANCH=$(printf '%s' "$PR_JSON" | jq -r '.headBranchName')
+          if [ -z "$BRANCH" ] || [ "$BRANCH" = "null" ]; then
+            echo "::error::Could not extract headBranchName from release-please output"
+            printf '%s\n' "$PR_JSON" | head -5
+            exit 1
+          fi
+          echo "name=$BRANCH" >> "$GITHUB_OUTPUT"
+
       - name: Checkout release-please branch
         if: ${{ steps.release.outputs.pr != '' }}
         uses: actions/checkout@v6
         with:
-          ref: ${{ fromJson(steps.release.outputs.pr).headBranchName }}
+          ref: ${{ steps.branch.outputs.name }}
           token: ${{ secrets.RELEASE_PLEASE_TOKEN }}
 
       - uses: actions-rust-lang/setup-rust-toolchain@v1
@@ -200,4 +224,4 @@ jobs:
           # tracking branch staying the default in future versions.
           git push origin "HEAD:${BRANCH}"
         env:
-          BRANCH: ${{ fromJson(steps.release.outputs.pr).headBranchName }}
+          BRANCH: ${{ steps.branch.outputs.name }}