👷 Add a GitHub workflow to prevent blocked PRs from being merged

[ebouchut]

Description

This PR adds a new feature to PRs in this GitHub repository.
A PR can depend on:

• another PR from the same repository
• a GitHub issue from the same repository

To indicate that PR2 depends on PR1,
add Blocked by #1 to PR2's description

This PR adds a new GitHub workflow (.github/workflows/pr-dependencies-check.yml) using the Levi-Lesches/blocking-issues GitHub Action.
It runs each time a PR is created, updated, closed, or re-opened.
It checks if the PR is blocked.
If so it fails, preventing the PR from being merged.

⏱️ The workflow takes ~10 seconds to run.

Remarks

PR Dependent on another PR

✅ This works fine provided both PRs are in the same repository.
Cross-repository PR dependencies are not supported.

PR Dependent on an Issue

I experimented with making a PR dependent on a GitHub Issue.
Based on my testing, it does not work as closing this issue does not trigger the workflow.
Therefore this dependency change is not taken into account automatically.
I needed to edit the PR description to trigger the workflow again which is not optimal!
❌ This is why, I do not recommend making a PR dependent on a GH issue.

EDIT: ✅ It now works fine. I made a mistake and the indentation was off. Now fixed.

Resources

• Levi-Lesches/blocking-issues GitHub Action: https://github.com/Levi-Lesches/blocking-issues
• Discussion about the need for such a feature in GitHub and the open-source workarounds in the meantime: https://github.com/orgs/community/discussions/4477#discussioncomment-1039627

[ebouchut]

This PR adds a GitHub Workflow to check for PRs blocked by another PR and/or issue.
It prevents the dependent PR from being merged while the blocking PR/issue is opened.

GitHub does not provide a way to mark a PR dependent on another PR.
For example, making PR-2 dependent on PR-1.

• PR-1 is the parent PR
• PR-2 is the child PR

While searching for open-source alternatives to fill this void,
I came across an interesting discussion on GitHub itself.
It was started a few years ago by @isaacs on his isaacs/github repo.
GitHub subsequently hired him, and the repo morphed into this discussion (now hosted on Github).

The need is twofold:

1. Be able to compare the difference between PR-1 (parent) and PR-2 (child).
2. Prevent PR-2 from being merged before PR-1 is merged

I have paraphrased above what is explained in this message:
https://github.com/orgs/community/discussions/4477#discussioncomment-1293255

A few tools answer point 2 (i.e. avoid an incorrect merge of the child PR before the parent PR):
https://github.com/orgs/community/discussions/4477#discussioncomment-1039627

I tried every one of them and decided to go with the blocking-issues Github Action.
https://github.com/Levi-Lesches/blocking-issues

A GitHub action to label issues and PRs when they're blocked by another issue or PR.

This PR adds a GitHub Workflow to check for PRs and GitHub issues blocked by another PR and/or Issue.
For instance, we can edit the description of PR-2 and mark it as blocked by PR-1 like this:

Blocked by #1

The workflow will now prevent PR-2 from being merged before PR-1 is merged.

[MikePlante1]

LGTM

[ebouchut]

Thanks @MikePlante1 .

❌ The workflow failed because it could not create the blocked label.
Could you create it by hand here like this and edit the PR description to re-trigger the checks:

[ebouchut]

ℹ️ For the record, the Checks of a PR may display this error

Error: Resource not accessible by integration

as long as it is in Draft mode.

To display the detailed the Checks logs, click the Details link next to

Prevent Blocked PRs from being Merged / blocking_issues (pull_request)