Integration-kit/template/server/scripts/swaggerFragment.js

#!/usr/bin/env node
// ── §2.8 — the OpenAPI fragment ───────────────────────────────────────────
//
// Generates (or checks) `swagger-fragment.json` in the bundle root: the paths,
// tags and schemas describing every route this module registers. Core merges the
// fragments of *started* modules over its own committed spec at request time and
// serves the result at `/api/docs.json` (MODULE_API.md §6.1a).
//
// ── Why a module has to ship this at all ──────────────────────────────────
//
// Core's own spec generation is STATIC analysis — swagger-autogen parses core's
// `app.js` as text and follows the literal `app.use(...)` chain. Your module
// arrives on a volume after core was built, is required by a filesystem loop, and
// mounts through `api.registerRoutes()`. There is no literal mount for a parser to
// follow, and core does not have your sources anyway. So nothing core can run
// will ever describe your routes.
//
// The failure mode is the dangerous one: swagger-autogen reports success and
// emits a spec with the routes simply absent. It happened twice inside core
// before anyone noticed, and once to the first module — 417 annotations that
// generated nothing at all, for two phases, because nobody had built the
// fragment. If you take one thing from this file, take that a green build is not
// evidence that anything was described.
//
// ── Where the prefixes come from ──────────────────────────────────────────
//
// swagger-autogen is pointed at one router file at a time, so its paths come out
// relative to that router (`/status`, not `/api/v1/public/world/status`) —
// nothing in the file says where it hangs. §6.1a requires fully-qualified paths,
// because core merges the fragment verbatim and never re-derives a prefix.
//
// So this script **runs your own `register()`** against a recording `api` and
// reads the mounts back out. Every prefix is therefore the prefix that router is
// actually registered under — the same call an operator's core will make, rather
// than a table beside it that drifts the first time a mount moves. Which file a
// recorded router object came from is answered by `require.cache`: the module
// whose `exports` IS that router.
//
// The tier base paths are the one thing that cannot be derived here, because they
// are core's and not yours. They are §2.4's normative table, quoted below.

const fs = require('fs')
const os = require('os')
const path = require('path')

const swaggerAutogen = require('swagger-autogen')({ openapi: '3.0.0' })

const { fakeCtx, fakeApi } = require('../test/_fakes')
const doc = require('../swagger/doc')

const MODULE_ROOT = path.resolve(__dirname, '..', '..')
const SERVER_ROOT = path.join(MODULE_ROOT, 'server')
const FRAGMENT = path.join(MODULE_ROOT, 'swagger-fragment.json')

// MODULE_API.md §2.4. A router registered under a tier sits inside that tier's
// router in core, behind its gate; the base path is core's and fixed.
const TIER_BASE = {
  public: '/api/v1/public',
  admin: '/api/v1/admin',
  player: '/api/v1/player',
}

/**
 * Run `register()` with a recording api and return `[{ file, prefix, what }]`.
 *
 * The ctx is the test fakes' — the same one the suite proves the module runs
 * against — because registration must not touch a database (§2.2), and this
 * script is exactly the kind of no-database caller that rule exists for.
 */
function mountedRouters() {
  const register = require('../index')
  const api = fakeApi()
  register(fakeCtx(), api)

  const fileOf = (router) => {
    for (const mod of Object.values(require.cache)) {
      if (mod && mod.exports === router) return mod.filename
    }
    return null
  }

  const mounts = []
  for (const [tier, byPrefix] of Object.entries(api.record.routes || {})) {
    const base = TIER_BASE[tier]
    if (!base) throw new Error(`swagger: registered under unknown tier "${tier}" — §2.4 has three`)
    for (const [prefix, router] of Object.entries(byPrefix)) {
      mounts.push({ router, prefix: base + prefix, what: `${tier}${prefix}` })
    }
  }

  return mounts.map(({ router, prefix, what }) => {
    const file = fileOf(router)
    if (!file) {
      // A router built inline in index.js rather than required from its own
      // file. swagger-autogen needs a file to read, so there is nothing to
      // generate from — put the router in its own module.
      throw new Error(`swagger: cannot find the source file of the router for ${what}`)
    }
    return { file, prefix, what }
  })
}

/**
 * Run swagger-autogen over one router file. Paths come out router-relative.
 *
 * **swagger-autogen reports a broken annotation and then succeeds anyway** — it
 * `console.error`s "Syntax error" or "out of structure", drops that one
 * annotation, and prints `Success` in green. So its diagnostics are captured here
 * and made fatal. Nothing else will tell you.
 */
async function fragmentFor(file) {
  const dir = fs.mkdtempSync(path.join(os.tmpdir(), 'module-swagger-'))
  const out = path.join(dir, 'fragment.json')

  const complaints = []
  const realError = console.error
  console.error = (...args) => {
    const line = args.map(String).join(' ')
    if (/syntax error|out of structure/i.test(line)) complaints.push(line.trim())
    else realError(...args)
  }
  try {
    // A DEEP COPY per call, and that is not defensive style. swagger-autogen
    // writes its result back into the object it was handed, so reusing one `doc`
    // across several routers re-wraps the previous pass's output every time. The
    // first module to hit this produced a 484 MB fragment from six routers.
    await swaggerAutogen(out, [path.relative(SERVER_ROOT, file).split(path.sep).join('/')], {
      ...JSON.parse(JSON.stringify(doc)),
      info: { title: 'examplegame fragment', version: '0' },
    })
  } finally {
    console.error = realError
  }
  if (complaints.length > 0) {
    throw new Error(
      `swagger: ${path.relative(MODULE_ROOT, file)} has ${complaints.length} annotation(s) ` +
        `swagger-autogen could not parse — it drops them and reports success:\n  ${complaints.join('\n  ')}`,
    )
  }

  const fragment = JSON.parse(fs.readFileSync(out, 'utf8'))
  fs.rmSync(dir, { recursive: true, force: true })
  return fragment
}

/**
 * Re-root a router-relative fragment under the prefix it is mounted at.
 *
 * Express path params (`:id`) become OpenAPI's (`{id}`), and any param belonging
 * to the PREFIX is moved to the front of each operation's parameter list —
 * swagger-autogen orders parameters by where they appeared in the path it saw,
 * which was only the tail.
 */
function prefixPaths(fragment, prefix) {
  const oas = prefix.replace(/:([A-Za-z0-9_]+)/g, '{$1}').replace(/\/+$/, '')
  const outer = [...oas.matchAll(/\{([A-Za-z0-9_]+)\}/g)].map((m) => m[1])
  const paths = {}
  for (const [p, item] of Object.entries(fragment.paths || {})) {
    for (const operation of Object.values(item)) {
      const params = operation && operation.parameters
      if (!Array.isArray(params)) continue
      const rank = (q) => {
        const i = outer.indexOf(q && q.name)
        return i === -1 ? outer.length : i
      }
      operation.parameters = params
        .map((q, i) => ({ q, i }))
        .sort((a, b) => rank(a.q) - rank(b.q) || a.i - b.i)
        .map(({ q }) => q)
    }
    // `router.get('/')` under a prefix concatenates to a trailing slash, a URL no
    // client calls. Core's generator normalises the same way.
    paths[`${oas}${p}`.replace(/\/$/, '')] = item
  }
  return paths
}

/**
 * Build the whole fragment: every mounted router, re-rooted and merged.
 *
 * Only `paths`, `tags` and `components.schemas` — the three sections §6.1a lets a
 * fragment carry. `info`, `servers` and the security schemes belong to the merged
 * document, which is to say to core.
 */
async function build() {
  const spec = { paths: {}, tags: [], components: { schemas: {} } }
  let shared = false

  for (const { file, prefix, what } of mountedRouters()) {
    const generated = await fragmentFor(file)
    // Tags and schemas are the same on every pass — each was handed the same
    // `doc` — so take them from whichever ran first. What lands in the fragment
    // has to be what swagger-autogen PRODUCED and not what it was given: those
    // two differ (see fragmentFor), and core merges this file verbatim into a
    // spec whose own schemas went through the same mill.
    if (!shared) {
      spec.tags = generated.tags || []
      spec.components.schemas = (generated.components || {}).schemas || {}
      shared = true
    }
    const paths = prefixPaths(generated, prefix)
    const count = Object.keys(paths).length
    if (count === 0) {
      // An empty result is precisely what the silent drop looks like, so it is a
      // hard failure rather than a router that happens to declare no routes.
      throw new Error(`swagger: ${what} (${path.relative(MODULE_ROOT, file)}) generated NO paths`)
    }
    for (const [p, item] of Object.entries(paths)) {
      if (spec.paths[p]) throw new Error(`swagger: two of this module's routers both document ${p}`)
      spec.paths[p] = item
    }
    process.stdout.write(`  ${String(count).padStart(3)} path(s)  ${prefix}  ← ${what}\n`)
  }

  // Sorted, because swagger-autogen emits router-traversal order: without this,
  // moving a route between files rewrites most of a committed artifact even when
  // the API is provably unchanged.
  spec.paths = Object.fromEntries(Object.entries(spec.paths).sort(([a], [b]) => (a < b ? -1 : 1)))
  return spec
}

async function main() {
  const check = process.argv.includes('--check')
  const spec = await build()
  const json = `${JSON.stringify(spec, null, 2)}\n`

  if (!check) {
    fs.writeFileSync(FRAGMENT, json)
    process.stdout.write(`\nwrote ${path.relative(MODULE_ROOT, FRAGMENT)} — ${Object.keys(spec.paths).length} paths\n`)
    return
  }

  if (!fs.existsSync(FRAGMENT)) {
    process.stderr.write('\nswagger-fragment.json is missing. Run `npm run swagger`.\n')
    process.exit(1)
  }
  if (fs.readFileSync(FRAGMENT, 'utf8') !== json) {
    process.stderr.write(
      '\nswagger-fragment.json is STALE — the routes or their annotations changed and it was not\n' +
        'regenerated. Run `npm run swagger` and commit the result. Core merges this file verbatim,\n' +
        'so a stale one documents a URL surface this module does not serve.\n',
    )
    process.exit(1)
  }
  process.stdout.write(`\nswagger-fragment.json is current — ${Object.keys(spec.paths).length} paths\n`)
}

if (require.main === module) {
  main().catch((err) => {
    process.stderr.write(`${err.stack}\n`)
    process.exit(1)
  })
}

module.exports = { mountedRouters, prefixPaths, build, TIER_BASE, FRAGMENT }