ci: Run full matrix only on Ready to merge or Full CI build labeled PRs (#7689)

Co-authored-by: Bart <bthomee@users.noreply.github.com>

.github/workflows/on-pr.yml

@@ -1,7 +1,11 @@
-# This workflow runs all workflows to check, build and test the project on
-# various Linux flavors, as well as on MacOS and Windows, on every push to a
-# user branch. However, it will not run if the pull request is a draft unless it
-# has the 'DraftRunCI' label. For commits to PRs that target a release branch,
+# This workflow runs workflows to check, build and test the project
+# on every meaningful change on pull_request.
+# However, it will not run if the PR is a draft
+# unless it has the 'DraftRunCI' or 'Full CI build' label.
+#
+# By default a PR builds only a minimal matrix.
+# The full matrix runs once the PR is labeled "Ready to merge" or "Full CI build".
+# For commits to PRs that target a release branch,
 # it also uploads the libxrpl recipe to the Conan remote.
 name: PR
 
@@ -15,9 +19,24 @@ on:
       - reopened
       - synchronize
       - ready_for_review
+      # Trigger on label changes so toggling "Ready to merge" or "Full CI build"
+      # switches between the minimal and full matrix without needing a new push.
+      - labeled
+      - unlabeled
 
 concurrency:
-  group: ${{ github.workflow }}-${{ github.ref }}
+  # Use a per-ref group so a newer run (a push, or a change to a label below)
+  # supersedes the in-progress one for that ref. Label events we don't act on get
+  # their own unique group (per run id) instead, keeping them out of the shared
+  # group so real builds keep running. Keep this list in sync with `should-run`.
+  group: >-
+    ${{ github.workflow }}-${{ github.ref }}${{
+      ((github.event.action == 'labeled' || github.event.action == 'unlabeled')
+      && github.event.label.name != 'Ready to merge'
+      && github.event.label.name != 'DraftRunCI'
+      && github.event.label.name != 'Full CI build')
+      && format('-{0}', github.run_id) || ''
+    }}
   cancel-in-progress: true
 
 defaults:
@@ -26,10 +45,21 @@ defaults:
 
 jobs:
   # This job determines whether the rest of the workflow should run. It runs
-  # when the PR is not a draft (which should also cover merge-group) or
-  # has the 'DraftRunCI' label.
+  # when the PR is not a draft (which should also cover merge-group) or has the
+  # 'DraftRunCI' or 'Full CI build' label. For label events it only runs when the
+  # label added or removed is one we act on ('Ready to merge', 'DraftRunCI' or
+  # 'Full CI build'), so unrelated label changes do not trigger a redundant run.
   should-run:
-    if: ${{ !github.event.pull_request.draft || contains(github.event.pull_request.labels.*.name, 'DraftRunCI') }}
+    if: >-
+      ${{
+        ((github.event.action != 'labeled' && github.event.action != 'unlabeled')
+          || github.event.label.name == 'Ready to merge'
+          || github.event.label.name == 'DraftRunCI'
+          || github.event.label.name == 'Full CI build')
+        && (!github.event.pull_request.draft
+          || contains(github.event.pull_request.labels.*.name, 'DraftRunCI')
+          || contains(github.event.pull_request.labels.*.name, 'Full CI build'))
+      }}
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repository
@@ -91,15 +121,17 @@ jobs:
         # least one of:
         # * Any of the files checked in the `changes` step were modified
         # * The PR is NOT a draft and is labeled "Ready to merge"
+        # * The PR is labeled "Full CI build" (draft or not)
         # * The workflow is running from the merge queue
         id: go
         env:
           FILES: ${{ steps.changes.outputs.any_changed }}
           DRAFT: ${{ github.event.pull_request.draft }}
           READY: ${{ contains(github.event.pull_request.labels.*.name, 'Ready to merge') }}
+          FULL: ${{ contains(github.event.pull_request.labels.*.name, 'Full CI build') }}
           MERGE: ${{ github.event_name == 'merge_group' }}
         run: |
-          echo "go=${{ (env.DRAFT != 'true' && env.READY == 'true') || env.FILES == 'true' || env.MERGE == 'true' }}" >>"${GITHUB_OUTPUT}"
+          echo "go=${{ (env.DRAFT != 'true' && env.READY == 'true') || env.FULL == 'true' || env.FILES == 'true' || env.MERGE == 'true' }}" >>"${GITHUB_OUTPUT}"
           cat "${GITHUB_OUTPUT}"
     outputs:
       go: ${{ steps.go.outputs.go == 'true' }}
@@ -142,7 +174,10 @@ jobs:
 
   package:
     needs: [should-run, build-test]
-    if: ${{ needs.should-run.outputs.go == 'true' }}
+    # Packaging consumes the debian/rhel release binaries, which are only built
+    # by the full matrix. Skip it for pull requests that ran only the minimal
+    # matrix (i.e. not yet labeled "Ready to merge" or "Full CI build").
+    if: ${{ needs.should-run.outputs.go == 'true' && (github.event_name != 'pull_request' || contains(github.event.pull_request.labels.*.name, 'Ready to merge') || contains(github.event.pull_request.labels.*.name, 'Full CI build')) }}
     uses: ./.github/workflows/reusable-package.yml
 
   upload-recipe:

.github/workflows/reusable-strategy-matrix.yml

@@ -35,5 +35,8 @@ jobs:
         id: generate
         env:
           GENERATE_CONFIG: ${{ inputs.os != '' && format('--config={0}', inputs.os) || '' }}
-          GENERATE_EVENT: ${{ github.event_name }}
-        run: ./generate.py ${GENERATE_CONFIG} --event="${GENERATE_EVENT}" >>"${GITHUB_OUTPUT}"
+          # Run only the minimal matrix for pull requests that are not yet
+          # labeled "Ready to merge" or "Full CI build". Any other event (merge
+          # queue, push, schedule, manual dispatch) runs the full matrix.
+          GENERATE_MINIMAL: ${{ (github.event_name == 'pull_request' && !contains(github.event.pull_request.labels.*.name, 'Ready to merge') && !contains(github.event.pull_request.labels.*.name, 'Full CI build')) && '--minimal' || '' }}
+        run: ./generate.py ${GENERATE_CONFIG} ${GENERATE_MINIMAL} >>"${GITHUB_OUTPUT}"