Iterator that loops over Github GraphQL API result using cursor

makeGithubGraphqlIterator.ts

import { getOctokit } from '@actions/github';
import { GraphQlQueryResponseData } from '@octokit/graphql';

const MAX_PAGE_SIZE = 100;

export interface IterableListSearch<Iterable> {
  nodes: Iterable[];
  pageInfo: PageInfo;
}

export interface IterableListQuery<Iterable> {
  edges: Array<{
    node: Iterable;
  }>;
  pageInfo: PageInfo;
}

export type IterableList<Iterable> =
  | IterableListQuery<Iterable>
  | IterableListSearch<Iterable>;

export async function* makeGraphqlIterator<IterableData>(
  octokit: ReturnType<typeof getOctokit>,
  query: string,
  parameters: object,
  extractListFunction: (
    response: GraphQlQueryResponseData,
  ) => IterableList<IterableData> | undefined,
): AsyncGenerator<IterableData> {
  let cursor: string | undefined = undefined;
  let hasNextPage: boolean = true;

  const { pageSize = MAX_PAGE_SIZE }: { pageSize?: number } = parameters;

  while (hasNextPage) {
    const response = await octokit.graphql<GraphQlQueryResponseData>(query, {
      ...parameters,
      endCursor: cursor,
      pageSize,
    });

    const list = extractListFunction(response);

    if (list === undefined) {
      return;
    }

    cursor = list.pageInfo.endCursor;
    hasNextPage = list.pageInfo.hasNextPage;

    let iterables: IterableData[] | undefined = undefined;

    if ('edges' in list) {
      iterables = list.edges.map(
        (edge: { node: IterableData }): IterableData => edge.node,
      );
    } else if ('nodes' in list) {
      iterables = list.nodes;
    } else {
      throw new Error('unexpected list format');
    }

    for (const iterable of iterables) {
      yield iterable;
    }
  }
}

Use it like:

const octokit = graphql.defaults({
  headers: {
    authorization: `token ${process.env.TOKEN}`,
  },
});

const parameters: {
    pullRequestNumber: number;
    repositoryName: string;
    repositoryOwner: string;
  } = { 
  // ... 
}

const query = `
  query FindPullRequestCommitAuthors($repositoryOwner: String!, $repositoryName: String!, $pullRequestNumber: Int!, $pageSize: Int!, $endCursor: String) {
    repository(owner: $repositoryOwner, name: $repositoryName) {
      pullRequest(number: $pullRequestNumber) {
        commits(first: $pageSize, after: $endCursor) {
          edges {
            node {
              commit {
                author {
                  user {
                    login
                  }
                }
              }
            }
          }
          pageInfo {
            endCursor
            hasNextPage
          }
        }
      }
    }
  }
`;

const iterator = makeGraphqlIterator<PullRequestCommitNode>(
  octokit,
  query,
  parameters,
  (response: GraphQlQueryResponseData): IterableList<PullRequestCommitNode> =>
    response.repository.pullRequest?.commits,
);

const firstResult: IteratorResult<PullRequestCommitNode> = await iterator.next();

if (firstResult.done === true) {
  logWarning('Could not find PR commits, aborting.');

  return true;
}

for await (const commitNode of iterator) {
  const { author } = commitNode.commit;

  // ...
}