fix(server): checkout fork PRs into owner branches

packages/server/src/services/github-service.test.ts

@@ -161,6 +161,34 @@ function pullRequestJson(title: string): string {
   ]);
 }
 
+function pullRequestCheckoutTargetJson(): string {
+  return JSON.stringify({
+    data: {
+      repository: {
+        pullRequest: {
+          number: 526,
+          baseRefName: "main",
+          headRefName: "main",
+          isCrossRepository: true,
+          headRepositoryOwner: { login: "therainisme" },
+          headRepository: {
+            sshUrl: "git@github.com:therainisme/paseo.git",
+            url: "https://github.com/therainisme/paseo",
+          },
+        },
+      },
+    },
+  });
+}
+
+function repoViewJson(): string {
+  return JSON.stringify({
+    owner: { login: "getpaseo" },
+    name: "paseo",
+    parent: null,
+  });
+}
+
 function issueJson(title: string): string {
   return JSON.stringify([
     {
@@ -275,6 +303,38 @@ describe("GitHubService", () => {
     expect(computeGithubNextInterval(stableStatus, 4)).toBe(EXPECTED_GITHUB_ERROR_BACKOFF_CAP_MS);
   });
 
+  it("loads pull request checkout target details through GraphQL", async () => {
+    const runner = createRunner([repoViewJson(), pullRequestCheckoutTargetJson()]);
+    const service = createGitHubService({
+      runner: runner.runner,
+      resolveGhPath: async () => "/usr/bin/gh",
+      now: () => 100,
+    });
+
+    await expect(
+      service.getPullRequestCheckoutTarget?.({ cwd: "/repo", number: 526 }),
+    ).resolves.toEqual({
+      number: 526,
+      baseRefName: "main",
+      headRefName: "main",
+      headOwnerLogin: "therainisme",
+      headRepositorySshUrl: "git@github.com:therainisme/paseo.git",
+      headRepositoryUrl: "https://github.com/therainisme/paseo",
+      isCrossRepository: true,
+    });
+
+    expect(runner.calls).toHaveLength(2);
+    expect(runner.calls[0]).toEqual({
+      cwd: "/repo",
+      args: ["repo", "view", "--json", "owner,name,parent"],
+    });
+    expect(runner.calls[1]?.cwd).toBe("/repo");
+    expect(runner.calls[1]?.args.slice(0, 3)).toEqual(["api", "graphql", "-f"]);
+    expect(runner.calls[1]?.args).toContain("owner=getpaseo");
+    expect(runner.calls[1]?.args).toContain("name=paseo");
+    expect(runner.calls[1]?.args).toContain("number=526");
+  });
+
   it("polls PR status at fast cadence while checks are pending", async () => {
     let now = 0;
     const runner = createRunner([

packages/server/src/services/github-service.ts

@@ -185,6 +185,53 @@ const GitHubRepoViewSchema = z.object({
     .optional(),
 });
 
+const PullRequestCheckoutTargetSchema = z.object({
+  data: z.object({
+    repository: z.object({
+      pullRequest: z
+        .object({
+          number: z.number(),
+          baseRefName: z.string().catch(""),
+          headRefName: z.string().catch(""),
+          isCrossRepository: z.boolean().catch(false),
+          headRepositoryOwner: z
+            .object({
+              login: z.string().catch(""),
+            })
+            .nullable()
+            .optional(),
+          headRepository: z
+            .object({
+              sshUrl: z.string().nullable().optional(),
+              url: z.string().nullable().optional(),
+            })
+            .nullable()
+            .optional(),
+        })
+        .nullable(),
+    }),
+  }),
+});
+
+const PULL_REQUEST_CHECKOUT_TARGET_QUERY = `
+query PullRequestCheckoutTarget($owner: String!, $name: String!, $number: Int!) {
+  repository(owner: $owner, name: $name) {
+    pullRequest(number: $number) {
+      number
+      baseRefName
+      headRefName
+      isCrossRepository
+      headRepositoryOwner {
+        login
+      }
+      headRepository {
+        sshUrl
+        url
+      }
+    }
+  }
+}`;
+
 const CURRENT_PR_STATUS_FIELDS =
   "number,url,title,state,isDraft,baseRefName,headRefName,mergedAt,statusCheckRollup,reviewDecision,headRepositoryOwner";
 
@@ -266,6 +313,16 @@ export interface GitHubPullRequestSummary {
   updatedAt: string;
 }
 
+export interface GitHubPullRequestCheckoutTarget {
+  number: number;
+  baseRefName: string;
+  headRefName: string;
+  headOwnerLogin: string | null;
+  headRepositorySshUrl: string | null;
+  headRepositoryUrl: string | null;
+  isCrossRepository: boolean;
+}
+
 export interface GitHubIssueSummary {
   number: number;
   title: string;
@@ -417,6 +474,9 @@ export interface GitHubService {
   listIssues(options: ListGitHubIssuesOptions): Promise<GitHubIssueSummary[]>;
   getPullRequest(options: GetGitHubPullRequestOptions): Promise<GitHubPullRequestSummary>;
   getPullRequestHeadRef(options: GetGitHubPullRequestOptions): Promise<string>;
+  getPullRequestCheckoutTarget?(
+    options: GetGitHubPullRequestOptions,
+  ): Promise<GitHubPullRequestCheckoutTarget>;
   getCurrentPullRequestStatus(
     options: {
       cwd: string;
@@ -756,6 +816,40 @@ export function createGitHubService(options: CreateGitHubServiceOptions = {}): G
       return pullRequest.headRefName;
     },
 
+    getPullRequestCheckoutTarget(options) {
+      return cached({
+        cwd: options.cwd,
+        method: "getPullRequestCheckoutTarget",
+        args: { number: options.number },
+        readOptions: options,
+        load: async () => {
+          const repo = await getGitHubRepoView({ cwd: options.cwd, run });
+          const owner = repo?.owner?.login;
+          const name = repo?.name;
+          if (!owner || !name) {
+            throw new Error("Unable to resolve GitHub repository for pull request checkout");
+          }
+
+          const stdout = await run(
+            [
+              "api",
+              "graphql",
+              "-f",
+              `query=${PULL_REQUEST_CHECKOUT_TARGET_QUERY}`,
+              "-F",
+              `owner=${owner}`,
+              "-F",
+              `name=${name}`,
+              "-F",
+              `number=${options.number}`,
+            ],
+            { cwd: options.cwd },
+          );
+          return parsePullRequestCheckoutTarget(stdout);
+        },
+      });
+    },
+
     getCurrentPullRequestStatus(options) {
       return cached({
         cwd: options.cwd,
@@ -1364,6 +1458,23 @@ function parsePullRequestSummary(stdout: string): GitHubPullRequestSummary {
   return toPullRequestSummary(GitHubPullRequestSummarySchema.parse(JSON.parse(stdout || "{}")));
 }
 
+function parsePullRequestCheckoutTarget(stdout: string): GitHubPullRequestCheckoutTarget {
+  const parsed = PullRequestCheckoutTargetSchema.parse(JSON.parse(stdout || "{}"));
+  const pullRequest = parsed.data.repository.pullRequest;
+  if (!pullRequest) {
+    throw new Error("Pull request not found");
+  }
+  return {
+    number: pullRequest.number,
+    baseRefName: pullRequest.baseRefName,
+    headRefName: pullRequest.headRefName,
+    headOwnerLogin: pullRequest.headRepositoryOwner?.login || null,
+    headRepositorySshUrl: pullRequest.headRepository?.sshUrl || null,
+    headRepositoryUrl: pullRequest.headRepository?.url || null,
+    isCrossRepository: pullRequest.isCrossRepository,
+  };
+}
+
 function toPullRequestSummary(
   item: z.infer<typeof GitHubPullRequestSummarySchema>,
 ): GitHubPullRequestSummary {