refactor(dev-infra): migrate github api in GitClient to rely on GithubClient (#37593)

GitClient now uses GithubClient for github API interactions.  GithubClient is
a class which extends Octokit and provides a member which allows for GraphQL
requests against the Github GraphQL api, as well as providing convenience methods
for common/repeated Github API requests.

PR Close #37593

dev-infra/utils/git/_github.ts

@@ -0,0 +1,100 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+/****************************************************************************
+ ****************************************************************************
+ ** DO NOT IMPORT THE GithubClient DIRECTLY, INSTEAD IMPORT GitClient from **
+ ** ./index.ts and access the GithubClient via the `.github` member.       **
+ ****************************************************************************
+ ****************************************************************************/
+
+import {graphql} from '@octokit/graphql';
+import * as Octokit from '@octokit/rest';
+import {RequestParameters} from '@octokit/types';
+import {query, types} from 'typed-graphqlify';
+
+/** Error for failed Github API requests. */
+export class GithubApiRequestError extends Error {
+  constructor(public status: number, message: string) {
+    super(message);
+  }
+}
+
+/**
+ * A Github client for interacting with the Github APIs.
+ *
+ * Additionally, provides convienience methods for actions which require multiple requests, or
+ * would provide value from memoized style responses.
+ **/
+export class _GithubClient extends Octokit {
+  /** The Github GraphQL (v4) API. */
+  graqhql: GithubGraphqlClient;
+
+  /** The current user based on checking against the Github API. */
+  private _currentUser: string|null = null;
+
+  constructor(token?: string) {
+    // Pass in authentication token to base Octokit class.
+    super({auth: token});
+
+    this.hook.error('request', error => {
+      // Wrap API errors in a known error class. This allows us to
+      // expect Github API errors better and in a non-ambiguous way.
+      throw new GithubApiRequestError(error.status, error.message);
+    });
+
+    // Create authenticated graphql client.
+    this.graqhql = new GithubGraphqlClient(token);
+  }
+
+  /** Retrieve the login of the current user from Github. */
+  async getCurrentUser() {
+    // If the current user has already been retrieved return the current user value again.
+    if (this._currentUser !== null) {
+      return this._currentUser;
+    }
+    const result = await this.graqhql.query({
+      viewer: {
+        login: types.string,
+      }
+    });
+    return this._currentUser = result.viewer.login;
+  }
+}
+
+/**
+ * An object representation of a GraphQL Query to be used as a response type and to generate
+ * a GraphQL query string.
+ */
+type GraphQLQueryObject = Parameters<typeof query>[1];
+
+/**
+ * A client for interacting with Github's GraphQL API.
+ *
+ * This class is intentionally not exported as it should always be access/used via a
+ * _GithubClient instance.
+ */
+class GithubGraphqlClient {
+  /** The Github GraphQL (v4) API. */
+  private graqhql = graphql;
+
+  constructor(token?: string) {
+    // Set the default headers to include authorization with the provided token for all
+    // graphQL calls.
+    if (token) {
+      this.graqhql.defaults({headers: {authorization: `token ${token}`}});
+    }
+  }
+
+
+  /** Perform a query using Github's GraphQL API. */
+  async query<T extends GraphQLQueryObject>(queryObject: T, params: RequestParameters = {}) {
+    const queryString = query(queryObject);
+    return (await this.graqhql(queryString, params)) as T;
+  }
+}