Composer plaform schema gets overwritten with old version

[andybroomfield]

Is there an existing issue for this?

• I have searched the existing issues

Package ecosystem

composer

Package manager version

2.8.1

Language version

PHP

Manifest location and content before the Dependabot update

In project root

dependabot.yml content

version: 2
updates:
  - package-ecosystem: "composer"
    directory: "/"
    schedule:
      interval: "weekly"
      day: "monday"
      time: "07:00"
      
    ignore:
      # Don't raise a separate PR for major drupal updates, 
      # Skip as we do these manually
      # Minor updates will be raised as separate PR
      # Only patch updates will be dealt with here
      - dependency-name: "drupal/core*"
        update-types: ["version-update:semver-major"]

    allow:
      # Allow both direct and indirect updates for all packages
      - dependency-type: "all"
    versioning-strategy: lockfile-only      
    
    groups:
      drupal-core-patches:
        patterns:
          - "drupal/core*"
        update-types:
          - "patch"
      contrib-module-updates:
        patterns:
          - "*" 
        exclude-patterns:
          - "drupal/core*"
        update-types:
          - "minor" 
          - "patch"  


  - package-ecosystem: "github-actions"
    directory: "/"
    schedule:
      interval: "weekly"
      day: "monday"
      time: "07:00"           

Updated dependency

All

What you expected to see, versus what you actually saw

The plaform section of composer.lock is being changed to the older schema (empty array) and not an object.
I would not expect this section to be updated.

This was noticed as we have a Github action that creates a build using Acquia BLT, which then errors with a dirty repository warning related to this change in composer.lock.

Current workaround is to checkout the dependabot PRs and run composer update --lock and push, which restores the platform schemas.

Native package manager behavior

Since composer 2.8, the platform and platform-dev sections are objects.
composer/composer#12123

Images of the diff or a link to the PR, issue, or logs

-    "platform": {},
-   "platform-dev": {},

+    "platform": [],
+    "platform-dev": [],

Smallest manifest that reproduces the issue

No response