feat(ng-dev): automatically close linked issues for non-main branches

When a pull request is merged into a non-main branch, GitHub does not automatically close the linked issues. This change ensures that linked issues are closed when a PR is merged into any branch, not just the main branch.

This is achieved by fetching the closing issue references for a pull request and then iterating through them to close any that are not already closed. This is handled in the merge strategies to ensure it happens after a successful merge.

Author: alan-agius4

ng-dev/pr/common/fetch-pull-request.ts

@@ -13,6 +13,7 @@ import {
   PullRequestState,
   StatusState,
   CommentAuthorAssociation,
+  IssueState,
 } from '@octokit/graphql-schema';
 import {getPendingPrs, getPr, getPrFiles, getPrComments} from '../../utils/github.js';
 import {alias, types as graphqlTypes, onUnion, optional, params} from 'typed-graphqlify';
@@ -133,6 +134,17 @@ export const PR_SCHEMA = {
   author: {
     login: graphqlTypes.string,
   },
+  closingIssuesReferences: params(
+    {first: 100},
+    {
+      nodes: [
+        {
+          number: graphqlTypes.number,
+          state: graphqlTypes.custom<IssueState>(),
+        },
+      ],
+    },
+  ),
 };
 
 export type PullRequestFromGithub = typeof PR_SCHEMA;

ng-dev/pr/merge/pull-request.ts

@@ -18,9 +18,16 @@ import {TEMP_PR_HEAD_BRANCH} from './strategies/strategy.js';
 import {mergeLabels} from '../common/labels/merge.js';
 import {PullRequestValidationFailure} from '../common/validation/validation-failure.js';
 import {AuthenticatedGitClient} from '../../utils/git/authenticated-git-client.js';
-import {GithubConfig, NgDevConfig, CaretakerConfig, GoogleSyncConfig} from '../../utils/config.js';
+import {GithubConfig, NgDevConfig} from '../../utils/config.js';
 import {PullRequestConfig, PullRequestValidationConfig} from '../config/index.js';
 import {targetLabels} from '../common/labels/target.js';
+import {IssueState} from '@octokit/graphql-schema';
+
+/** Interface describing a pull request's closing issue references. */
+export interface PullRequestClosingIssuesReferences {
+  number: number;
+  state: IssueState;
+}
 
 /** Interface that describes a pull request. */
 export interface PullRequest {
@@ -52,6 +59,8 @@ export interface PullRequest {
   validationFailures: PullRequestValidationFailure[];
   /** The SHA for the latest commit in the pull request. */
   headSha: string;
+  /** A list of issues that will be closed by the pull request. */
+  closingIssuesReferences: PullRequestClosingIssuesReferences[];
 }
 
 /**
@@ -155,5 +164,6 @@ export async function loadAndValidatePullRequest(
     title: prData.title,
     commitCount: prData.commits.totalCount,
     headSha: prData.headRefOid,
+    closingIssuesReferences: prData.closingIssuesReferences.nodes,
   };
 }

ng-dev/pr/merge/strategies/api-merge.ts

@@ -152,6 +152,13 @@ export class GithubApiMergeStrategy extends AutosquashMergeStrategy {
       );
     }
 
+    // When a pull request is merged, GitHub automatically closes any linked issues.
+    // This is not the case when the pull request is not merged into the main branch.
+    // This is why we need to manually close the linked issues.
+    if (githubTargetBranch !== this.git.mainBranchName) {
+      await this.closeLinkedIssues(pullRequest);
+    }
+
     // Workaround for fatal: refusing to fetch into branch 'refs/heads/merge_pr_target_main' checked out at ...
     // Cannot find where but `merge_pr_target_main` is being set as the current branch.
     // TODO: remove after finding the root cause.

ng-dev/pr/merge/strategies/autosquash-merge.ts

@@ -100,6 +100,11 @@ export class AutosquashMergeStrategy extends MergeStrategy {
         pull_number: pullRequest.prNumber,
         state: 'closed',
       });
+
+      // When a pull request is merged, GitHub automatically closes any linked issues.
+      // This is not the case when the pull request is not merged into the main branch.
+      // This is why we need to manually close the linked issues.
+      await this.closeLinkedIssues(pullRequest);
     }
   }
 }

ng-dev/pr/merge/strategies/strategy.ts

@@ -226,4 +226,37 @@ export abstract class MergeStrategy {
         `${banchesAndSha.map(([branch, sha]) => `- ${branch}: ${sha}`).join('\n')}`,
     });
   }
+
+  /**
+   * Manually closes issues linked to a merged Pull Request.
+   *
+   * This function addresses the scenario where **GitHub's automatic issue closure feature is skipped**
+   * because the PR's target branch is *not* the repository's main branch.
+   *
+   * It updates any open linked issues to a `closed` state with a `completed` reason.
+   *
+   * @note The method is a **no-op** if the PR target is the main branch,
+   * as GitHub handles issue closure automatically in that case.
+   */
+  protected async closeLinkedIssues({
+    closingIssuesReferences,
+    githubTargetBranch,
+  }: PullRequest): Promise<void> {
+    if (githubTargetBranch === this.git.mainBranchName) {
+      return;
+    }
+
+    for (const {number: issue_number, state} of closingIssuesReferences) {
+      if (state === 'CLOSED') {
+        continue;
+      }
+
+      await this.git.github.issues.update({
+        ...this.git.remoteParams,
+        issue_number,
+        state_reason: 'completed',
+        state: 'closed',
+      });
+    }
+  }
 }