fix: handle missing fork repo

lib/handle-pull-request.test.ts

@@ -53,6 +53,24 @@ describe("handlePullRequest", () => {
     ]);
   });
 
+  test("pull request without head repo is not treated as fork", async () => {
+    const createComment = vi.spyOn(comment, "createComment");
+    const eventPath = generatePullRequestWebhook({
+      body: "Pull request body\n/schedule 2022-06-12",
+      headRepo: null,
+    });
+    process.env.GITHUB_EVENT_PATH = eventPath;
+
+    await handlePullRequest();
+
+    expect(stdMocks.flush().stdout).toEqual([
+      "Handling pull request opened for https://github.com/gr2m/merge-schedule-action/pull/2\n",
+      `Schedule date found: "2022-06-12"\n`,
+      `Comment created: https://github.com/gr2m/merge-schedule-action/issues/2#issuecomment-22\n`,
+    ]);
+    expect(createComment.mock.calls).toHaveLength(1);
+  });
+
   test("no schedule command", async () => {
     const eventPath = generatePullRequestWebhook();
     process.env.GITHUB_EVENT_PATH = eventPath;

lib/utils.ts

@@ -6,7 +6,7 @@ export function hasScheduleCommand(text: string | null): boolean {
 }
 
 export function isFork(pullRequest: SimplePullRequest): boolean {
-  return pullRequest.head.repo.fork;
+  return Boolean(pullRequest.head?.repo?.fork);
 }
 
 export function getScheduleDateString(text: string | null): string {

test/utils.ts

@@ -17,13 +17,15 @@ type PullRequestWebhookOptions = {
   state?: "open" | "closed";
   body?: string;
   fork?: boolean;
+  headRepo?: { fork?: boolean } | null;
 };
 
 export function generatePullRequestWebhook({
   number = 2,
   state = "open",
   body = "Simple body",
   fork = false,
+  headRepo = undefined,
 }: PullRequestWebhookOptions = {}) {
   // https://docs.github.com/en/developers/webhooks-and-events/webhooks/webhook-events-and-payloads#webhook-payload-example-33
   const payload = {
@@ -34,7 +36,7 @@ export function generatePullRequestWebhook({
       state,
       body,
       head: {
-        repo: {
+        repo: headRepo ?? {
           fork,
         },
       },