Linked-versions internal merge is misconfigured

[luxaritas]

Environment details

GitHub Actions ubuntu-latest with release-please-action 3.7.1

Steps to reproduce

I've attempted to configure two linked-versions plugins to create two separate groups, like so:

{
  "$schema": "https://raw.githubusercontent.com/googleapis/release-please/main/schemas/config.json",
  "plugins": [
    {
      "type": "node-workspace",
      "merge": false
    },
    {
      "type": "linked-versions",
      "groupName": "groupa",
      "components": [
        "groupa",
        "packages-groupa-pkga1",
        "packages-groupa-pkga2"
      ],
      "merge": false
    },
    {
      "type": "linked-versions",
      "groupName": "groupb",
      "components": [
        "groupb",
        "packages-groupb-pkgb1",
        "packages-groupb-pkgb2"
      ],
      "merge": false
    }
  ],
  "packages": {
    "packages/groupa": {
      "component": "groupa",
      "release-type": "simple"
    },
    "packages/groupa/pkga1": {
      "component": "packages-groupa-pkga1",
      "skip-github-release": true
    },
    "packages/groupa/pkga2": {
      "component": "packages-groupa-pkga2",
      "skip-github-release": true
    },
    "packages/groupb": {
      "component": "groupb",
      "release-type": "simple"
    },
    "packages/groupb/pkgb1": {
      "component": "packages-groupb-pkgb1",
      "skip-github-release": true
    },
    "packages/groupb/pkgb2": {
      "component": "packages-groupb-pkgb2",
      "skip-github-release": true
    }
  }
}

However, only the second group makes it to the release PR. It seems like this is due to the following error:

pull request missing version {
  path: '.',
  pullRequest: {
    title: PullRequestTitle {
      version: undefined,
      component: undefined,
      targetBranch: 'main',
      pullRequestTitlePattern: 'chore${scope}: release groupa libraries',
      matchPattern: /^chore(\((?<branch>[\w-./]+)\))?: release groupa libraries$/
    },
    body: PullRequestBody {
      header: ':robot: I have created a release *beep* *boop*',
      footer: 'This PR was generated with [Release Please](https://github.com/googleapis/release-please). See [documentation](https://github.com/googleapis/release-please#release-please).',
      extra: undefined,
      releaseData: [Array],
      useComponents: true
    },
    updates: [
      [Object], [Object],
      [Object], [Object],
      [Object], [Object],
      [Object], [Object],
      [Object], [Object],
      [Object], [Object],
      [Object]
    ],
    labels: [ 'autorelease: pending' ],
    headRefName: 'release-please--branches--main',
    draft: false
  },
  config: { releaseType: 'simple' }
}

Analysis

My understanding of this is that when the first linked-versions plugin does its internal merge, it creates a PR without a version, and then the second linked-version plugin throws out that PR even though it is out of scope. Additionally, this is complicated by the fact that linked-versions does not honor the merge configuration property, as it is never passed when constructed by its plugin factory.

Resolution

I see two potential resolutions here:

1. Regardless, the plugin should respect "merge": false. I've confirmed that modifying the plugin factory to pass additional options like the workspace plugins do resolves the issue and results in all packages being included in the release
2. I imagine it would still be nice to allow two linked-versions plugins to coexist and create separate PRs. What is the reason for ensuring a PR version when doing the merge? Can it be only verified for in-scope candidates, or maybe even removed entirely? This check is done in WorkspacePlugin as well, and it isn't clear why.

[luxaritas]

Another possible option here would be to allow the merge plugin to accept a version directly, which could also be desirable as that way if you have a separate release PR for different sets of linked packages, they can eg include their shared version in the PR title

[luxaritas]

NB: The configuration for the setup of one-pr-per-group is a bit weird currently. You'd need separate-pull-requests to be off in the root config (to skip adding the final merge plugin), but it would need to be enabled for each package in the group (so that the linked-versions' merge includes them). Probably there should either be a separate root config option to enable or disable the final merge separate from setting the default for inclusion of all packages, or maybe there should be a setting on the linked-versions plugin to determine whether or not its combined PR should be noted as a separate PR or not (the latter is probably more flexible).