Using Google Script REST API (script_v1) from within GAS

googleapis.ts

import { script_v1 } from 'googleapis'

import { request } from './request'

#
# - You might want to call Script REST API from within GAS
# - googleapis node client does not work on GAS
# - You still want to re-use type definitions
#
# If you need more entries, check 
# https://github.com/googleapis/google-api-nodejs-client/blob/main/src/apis/script/v1.ts
#

export type GoogleAPis = {
  script: {
    projects: {
      create: (
        body: script_v1.Params$Resource$Projects$Create['requestBody'],
        params?: Omit<script_v1.Params$Resource$Projects$Create, 'requestBody'>
      ) => script_v1.Schema$Project
      get: (
        scriptId: string,
        params?: script_v1.Params$Resource$Projects$Get
      ) => script_v1.Schema$Project
    }
  }
}
          
export const googleapis: GoogleAPis = {
  script: {
    projects: {
      create: (
        body: script_v1.Params$Resource$Projects$Create['requestBody'],
        params?: Omit<script_v1.Params$Resource$Projects$Create, 'requestBody'>
      ) =>
        request<script_v1.Schema$Project>({
          path: `projects`,
          method: 'post',
          params,
          body,
        }),
      get: (
        scriptId: string,
        params?: script_v1.Params$Resource$Projects$Get
      ) =>
        request<script_v1.Schema$Project>({
          path: `projects/${scriptId}`,
          method: 'get',
          params,
        })
    }
  }
}

request.ts

const URL = 'https://script.googleapis.com/v1'

const e = encodeURIComponent

const makeQueryString = (params?: any): string =>
  params
    ? Object.keys(params)
        .map((key) => `${e(key)}=${e(params[key])}`)
        .join('&')
    : ''

export function request<T>(meta: {
  path: string
  method: GoogleAppsScript.URL_Fetch.HttpMethod
  params?: any
  body?: any
}): T {
  const queryString = makeQueryString(meta.params)
  const url = `${URL}/${meta.path}${queryString && '?' + queryString}`
  const res = UrlFetchApp.fetch(url, {
    method: meta.method,
    headers: { Authorization: `Bearer ${ScriptApp.getOAuthToken()}` },
    contentType: 'application/json',
    payload: meta.body ? JSON.stringify(meta.body) : undefined,
    muteHttpExceptions: true,
  })
  if (res.getResponseCode() >= 400) throw new Error(res.getContentText())
  return JSON.parse(res.getContentText()) as T
}