ci: try to fix runner selection

Author: rjaegers

.github/workflows/wc-build-push.yml

@@ -31,8 +31,12 @@ on:
         default: '{"runner": ["ubuntu-latest", "ubuntu-24.04-arm"]}'
       default-runner-labels:
         description: >-
-          String or JSON array of runner labels for non-build jobs.
-          Example: ["self-hosted", "linux", "x86_64"] or ubuntu-latest.
+          Single runner label OR JSON array of runner labels for non-build jobs.
+          Examples:
+            ubuntu-latest
+            ["ubuntu-latest"]
+            ["self-hosted", "linux", "x86_64"]
+          Provide a valid JSON array (starting with '[') to use multiple labels; any other value is treated as a single label string.
         required: false
         type: string
         default: ubuntu-latest
@@ -123,7 +127,9 @@ jobs:
           retention-days: 1
 
   merge-image:
-    runs-on: ${{ fromJson(inputs.default-runner-labels) }}
+    # Support either a plain single label (e.g. ubuntu-latest) OR a JSON array of labels.
+    # If the input starts & ends with brackets we attempt JSON parsing; otherwise we pass the raw string.
+    runs-on: ${{ (startsWith(inputs.default-runner-labels, '[') && endsWith(inputs.default-runner-labels, ']')) && fromJson(inputs.default-runner-labels) || inputs.default-runner-labels }}
     needs:
       - build-push
       - sanitize-image-name

.github/workflows/wc-sanitize-image-name.yml

@@ -13,7 +13,10 @@ on:
         required: true
         type: string
       runner-labels:
-        description: "Runner to use for the job, will be passed to `runs-on`"
+        description: >-
+          Runner selection for this job. Accepts either a single label (e.g. ubuntu-latest)
+          or a JSON array of labels (e.g. ["self-hosted", "linux", "x86_64"]).
+          If the value begins with '[' it will be parsed as JSON.
         required: true
         type: string
     outputs:
@@ -31,7 +34,8 @@ permissions: {}
 
 jobs:
   sanitize-inputs:
-    runs-on: ${{ fromJson(inputs.runner-labels) }}
+    # Allow either raw single label or JSON array of labels
+    runs-on: ${{ (startsWith(inputs.runner-labels, '[') && endsWith(inputs.runner-labels, ']')) && fromJson(inputs.runner-labels) || inputs.runner-labels }}
     outputs:
       image-basename: ${{ steps.sanitize-image-name.outputs.sanitized-basename }}
       image-name: ${{ steps.sanitize-image-name.outputs.sanitized-image-name }}