Read the semver label of a pull request when the job runs

.github/workflows/chart-pr.yml

@@ -28,11 +28,17 @@ jobs:
     outputs:
       bump: ${{ steps.label.outputs.bump }}
     steps:
+      # The labels the pull request has now, not the ones of the event that started the run: a pull
+      # request opened with a label (gh pr create --label) gets it right after the `opened` event, and
+      # the `labeled` event of the workflow token starts no run. Reading them now also lets a re-run
+      # pick up a label added later.
       - name: Read the semver label
         id: label
         env:
-          LABELS: ${{ toJSON(github.event.pull_request.labels.*.name) }}
+          GH_TOKEN: ${{ github.token }}
+          PR: ${{ github.event.pull_request.number }}
         run: |
+          LABELS=$(gh api "repos/$GITHUB_REPOSITORY/pulls/$PR" --jq '[.labels[].name]')
           bumps=$(jq -r '[.[] | select(. == "major" or . == "minor" or . == "patch")] | join(" ")' <<< "$LABELS")
           if [ "$(wc -w <<< "$bumps")" -ne 1 ]; then
             echo "::error::The pull request needs exactly one of the labels major, minor or patch (found: ${bumps:-none})"

.github/workflows/semver-version.yml

@@ -58,17 +58,18 @@ jobs:
           path: semver-workflows
           persist-credentials: false
 
-      # on a push, the labels of the pull request the pushed commit was merged from
+      # On a pull request, the labels it has now, not the ones of the event that started the run (see
+      # chart-pr.yml). On a push, the labels of the pull request the pushed commit was merged from.
       - name: Read the semver label
         id: label
         env:
           GH_TOKEN: ${{ github.token }}
           EVENT: ${{ github.event_name }}
-          PR_LABELS: ${{ toJSON(github.event.pull_request.labels.*.name) }}
+          PR: ${{ github.event.pull_request.number }}
           SHA: ${{ github.sha }}
         run: |
           if [ "$EVENT" = pull_request ]; then
-            labels="$PR_LABELS"
+            labels=$(gh api "repos/$GITHUB_REPOSITORY/pulls/$PR" --jq '[.labels[].name]')
           else
             pr=$(gh api "repos/$GITHUB_REPOSITORY/commits/$SHA/pulls" \
               --jq '[.[] | select(.merged_at != null)][0] // empty | {number, labels: [.labels[].name]}')

README.md

@@ -33,7 +33,7 @@ jobs:
 
 For repositories that release Helm charts from a `charts/` directory, with the version of each chart driven by the semver label of the pull request that changes it. On every pull request it:
 
-1. requires exactly one of the labels `major`, `minor` or `patch`, and comments on the pull request when it is missing;
+1. requires exactly one of the labels `major`, `minor` or `patch`, and comments on the pull request when it is missing. The labels are read when the job runs, not from the event that started it, so a label added right after the pull request was opened counts, and re-running the job picks up a label added later;
 2. bumps the `version` of every chart the pull request changes: its version on the base branch, bumped by the label. A chart that is not on the base branch yet keeps its version;
 3. commits the new versions ("Update helm chart versions") to the pull request branch. A pull request from a fork, which the workflow token cannot push to, fails instead, listing the versions its author has to set.
 
@@ -141,7 +141,7 @@ The chart version is bumped in the pull request itself because pull requests ope
 
 For repositories that release an application, not charts, with the version driven by the semver label of the pull request. It works out the version and leaves the build and the release to the caller:
 
-- on a pull request, it requires exactly one of the labels `major`, `minor` or `patch`, commenting on the pull request when it is missing, and returns `X.Y.Z-PRE-<pull request number>`;
+- on a pull request, it requires exactly one of the labels `major`, `minor` or `patch` (read when the job runs, as in `chart-pr.yml`), commenting on the pull request when it is missing, and returns `X.Y.Z-PRE-<pull request number>`;
 - on a push to the main branch, it reads the label of the pull request the pushed commit was merged from, and returns `X.Y.Z`. A commit that no merged pull request contains, or one merged without a label, fails.
 
 `X.Y.Z` is the highest release tag bumped by the label. Release tags are `<tag-prefix>X.Y.Z`; other tags, such as pre-releases (`1.2.3-PRE-4`), are ignored.