Function fetchGhPR

packages/shared/pr-github.ts:154–275

(
  runtime: PRRuntime,
  ref: GhPRRef,
)

}

export async function fetchGhPR(
  runtime: PRRuntime,
  ref: GhPRRef,
): Promise<{ metadata: PRMetadata; rawPatch: string; patchIncomplete?: boolean }> {
  const repo = repoFlag(ref);

  // Fetch diff, metadata, and repository defaults in parallel.
  const [diffResult, viewResult, repoResult] = await Promise.all([
    runtime.runCommand("gh", [
      "pr", "diff", String(ref.number),
      "--repo", repo,
    ]),
    runtime.runCommand("gh", [
      "pr", "view", String(ref.number),
      "--repo", repo,
      "--json", "id,title,author,baseRefName,headRefName,baseRefOid,headRefOid,url,changedFiles",
    ]),
    runtime.runCommand("gh", [
      "repo", "view", repo,
      "--json", "defaultBranchRef",
      "--jq", ".defaultBranchRef.name",
    ]),
  ]);

  if (viewResult.exitCode !== 0) {
    throw new Error(
      `Failed to fetch PR metadata: ${viewResult.stderr.trim() || `exit code ${viewResult.exitCode}`}`,
    );
  }

  // Resolve the patch. Primary: `gh pr diff` — one server-rendered document,
  // perfect fidelity. GitHub refuses to render it for very large PRs (406 /
  // "diff exceeded the maximum number of lines"); in that case fetch the same
  // diff file-by-file from the paginated files API and stitch it back together.
  let rawPatch: string;
  let patchIncomplete = false;
  if (diffResult.exitCode === 0) {
    rawPatch = diffResult.stdout;
  } else {
    const filesResult = await runtime.runCommand("gh", hostnameArgs(ref.host, [
      "api",
      `repos/${ref.owner}/${ref.repo}/pulls/${ref.number}/files?per_page=100`,
      "--paginate",
    ]));
    if (filesResult.exitCode !== 0) {
      const diffErr = diffResult.stderr.trim() || `exit code ${diffResult.exitCode}`;
      const filesErr = filesResult.stderr.trim() || `exit code ${filesResult.exitCode}`;
      throw new Error(`Failed to fetch PR diff (pr diff: ${diffErr}; files API: ${filesErr}).`);
    }
    const fileEntries = parsePaginatedArray<GitHubFileEntry>(filesResult.stdout);
    rawPatch = reconstructGhPatch(fileEntries);
    if (!rawPatch.trim()) {
      throw new Error(
        "PR diff is empty — it may be too large to fetch via the GitHub API. Review it on the GitHub web UI.",
      );
    }
    // The files API silently caps at 3000 files — never present a truncated
    // review as complete.