Function linkSubIssue

actions/setup/js/handle_agent_failure.cjs:693–726

* Link an issue as a sub-issue to a parent issue * @param {string} parentNodeId - GraphQL node ID of the parent issue * @param {string} subIssueNodeId - GraphQL node ID of the sub-issue * @param {number} parentNumber - Parent issue number (for logging) * @param {number} subIssueNumber - Sub-issu

(parentNodeId, subIssueNodeId, parentNumber, subIssueNumber)

 * @param {number} subIssueNumber - Sub-issue number (for logging)
 */
async function linkSubIssue(parentNodeId, subIssueNodeId, parentNumber, subIssueNumber) {
  core.info(`Linking issue #${subIssueNumber} as sub-issue of #${parentNumber}`);

  try {
    // Use GraphQL to link the sub-issue
    await github.graphql(
      `mutation($parentId: ID!, $subIssueId: ID!) {
        addSubIssue(input: {issueId: $parentId, subIssueId: $subIssueId}) {
          issue {
            id
            number
          }
          subIssue {
            id
            number
          }
        }
      }`,
      {
        parentId: parentNodeId,
        subIssueId: subIssueNodeId,
      }
    );

    core.info(`✓ Successfully linked #${subIssueNumber} as sub-issue of #${parentNumber}`);
  } catch (error) {
    const errorMessage = getErrorMessage(error);
    if (errorMessage.includes("Field 'addSubIssue' doesn't exist") || errorMessage.includes("not yet available")) {
      core.warning(`Sub-issue API not available. Issue #${subIssueNumber} created but not linked to parent.`);
    } else {
      core.warning(`Failed to link sub-issue: ${errorMessage}`);
    }
  }
}

/**
 * Build create_discussion errors context string from error environment variable