GraphQL to find PR associated with branch

This about a mini adventure to find which PR(s) belong to which branch using GitHub GraphQL for a GitHub Action project.

Introduction to GraphQL

GraphQL is a query language.

See the quick introduction in the docs but, essentially, we are working with

• Connection: Like SQL these let you query related objects in the same call. E.g. associatedPullRequests is a connection between a branch (ref) and a pull request.
• Nodes: Generic term for an object. We are interested in the pullrequest object
• Edge: Represents connections between nodes e.g. pull request(s) that are associated with a PR

Here is the query we are using to find which PR(s) are associated with a given commit (only using the first one found so far):

{
  repository(name: "example-repo", owner: "ftclausen") {
    ref(qualifiedName:"topic/some_branch") {
      associatedPullRequests(first: 1) {
        edges {
          node {
            number
            title
            baseRef {
              name
            }
          }
        }
      }
    }
  }
}

This then returns the following data

{
  "data": {
    "repository": {
      "ref": {
        "associatedPullRequests": {
          "edges": [
            {
              "node": {
                "number": 55,
                "title": "This is an example pull request",
                "baseRef": {
                  "name": "main"
                }
              }
            }
          ]
        }
      }
    }
  }
}

As best I understand edges will always be an array. Finally this can be imagined graphically which I find useful:

We then pull the above data in and use it as needed

How to represent types for GraphQL data

Given GraphQL data varies per type I followed this very helpful guide guide to generate types for GraphQL responses instead of manually doing it. Please see that for a concrete example.

A note on the concept of a Pull Request

We have three different ways pull requests are represented depending on the context:

• Pull Request Event: When a new PR is created we get a pull_request event payload
• REST API Pull Request response
• Pull Request from GraphQL response

So that is something to be aware of when working with TypeScript. I had to make my own meta-object to unify this for my purposes; this meta-object extracted just what I needed out of each one of the above types.