Module-uo/server/test/checkImports.test.js

// The boundary check, checked.
//
// `scripts/checkImports.js` is the acceptance test for the whole module contract
// (MODULE_API.md §5.1), and a check that has never been shown to fail is a check
// nobody knows the state of. These point it at fixtures that break each rule and
// assert it says so — and at prose that merely *describes* breaking them, which
// is what it got wrong the first time it was run.
//
// **Every fixture is a template literal, and that is load-bearing.** The scanner
// reads the files in this directory too, so an ordinary quoted string holding
// `require('../../x')` would make this file fail the very check it is testing.
// Templates are blanked by the stripper for exactly this class of text: source
// being composed as data is not source being imported.

const test = require('node:test')
const assert = require('node:assert')
const fs = require('node:fs')
const os = require('node:os')
const path = require('node:path')

const { scan, stripCommentsAndTemplates, SERVER_ROOT, MODULE_ROOT } = require('../scripts/checkImports')

/** Write `files` into a throwaway module tree and scan it. */
function scanFixture(files, { dev = new Set() } = {}) {
  const root = fs.mkdtempSync(path.join(os.tmpdir(), 'module-uo-'))
  const src = path.join(root, 'server')
  for (const [name, source] of Object.entries(files)) {
    const file = path.join(src, name)
    fs.mkdirSync(path.dirname(file), { recursive: true })
    fs.writeFileSync(file, source)
  }
  try {
    return scan(src, root, { shipped: (f) => !f.startsWith(path.join(src, 'test') + path.sep), dev })
  } finally {
    fs.rmSync(root, { recursive: true, force: true })
  }
}

test('the real server half is clean', () => {
  assert.deepStrictEqual(scan(SERVER_ROOT, MODULE_ROOT), [])
})

test('catches a relative path that escapes the module root', () => {
  const found = scanFixture({ 'a.js': `require('../../server/src/utils/db')` })
  assert.strictEqual(found.length, 1)
  assert.strictEqual(found[0].why, 'escapes the module root')
})

test('allows a relative path that stays inside it, however deep', () => {
  assert.deepStrictEqual(
    scanFixture({ 'deep/nested/a.js': `require('../../../module.json')` }),
    [],
  )
})

test('catches an absolute path', () => {
  const found = scanFixture({ 'a.js': `require('/etc/passwd')` })
  assert.strictEqual(found[0].why, 'absolute path')
})

test('catches a bare specifier in shipped code, even a devDependency', () => {
  // The rule that makes the boundary real: express arrives on ctx. A shipped
  // file requiring it would fail on a real install, because a module lives
  // outside core's server/ and never reaches core's node_modules.
  const found = scanFixture({ 'a.js': `const express = require('express')` }, { dev: new Set(['express']) })
  assert.strictEqual(found.length, 1)
  assert.match(found[0].why, /should this come from ctx/)
})

test('allows a devDependency in test code, which never runs inside core', () => {
  assert.deepStrictEqual(
    scanFixture({ 'test/a.js': `const express = require('express')` }, { dev: new Set(['express']) }),
    [],
  )
})

test('allows node builtins anywhere, with or without the node: prefix', () => {
  assert.deepStrictEqual(
    scanFixture({ 'a.js': `require('path'); require('node:fs'); import crypto from 'node:crypto'` }),
    [],
  )
})

test('allows node:test, which older Node versions omit from builtinModules', () => {
  // The first CI run failed on exactly this and on nothing else: `builtinModules`
  // omits `test` on Node 20 and includes it on Node 24, so every test file in
  // this suite was reported as breaking the module boundary. The check asks
  // Node (`isBuiltin`) rather than rebuilding the list, and treats the `node:`
  // prefix as sufficient on its own — a prefixed specifier can never resolve to
  // a package, whatever the running version enumerates.
  assert.deepStrictEqual(
    scanFixture({ 'a.js': `require('node:test'); require('node:test/reporters')` }),
    [],
  )
})

test('catches ESM and dynamic forms, not only require()', () => {
  const found = scanFixture({
    'a.js': [`import db from '../../core/db.js'`, `const x = await import('../../core/other.js')`].join('\n'),
  })
  assert.strictEqual(found.length, 2)
})

test('ignores a violation that is only DESCRIBED in a comment', () => {
  // The first run of this check failed on its own documentation, and on
  // index.js's comment explaining why the module must never require('express').
  // Prose about the rule must not trip the rule.
  assert.deepStrictEqual(
    scanFixture({
      'a.js': [
        `// Never write require("../../server/src/utils/db") - it escapes the module root.`,
        `/* Nor import express from "express": core hands it over on ctx. */`,
        `const path = require('path')`,
      ].join('\n'),
    }),
    [],
  )
})

test('ignores a specifier-shaped string inside a template literal', () => {
  assert.deepStrictEqual(
    scanFixture({ 'a.js': ['const sql = ', '`SELECT 1 -- require("../../x")`'].join('') }),
    [],
  )
})

test('a comment opener inside a string does not swallow the rest of the file', () => {
  // The reason this is a character walk and not a regexp: a URL in a string
  // contains `//`, and treating that as a comment would blank everything after
  // it — turning the check into one that silently passes.
  const found = scanFixture({
    'a.js': [`const url = 'https://example.com/x'`, `require('../../escaped')`].join('\n'),
  })
  assert.strictEqual(found.length, 1, 'the specifier after a URL string was missed')
})

test('a quote inside a comment does not swallow the rest of the file', () => {
  const found = scanFixture({
    'a.js': [`// don't do this`, `require('../../escaped')`].join('\n'),
  })
  assert.strictEqual(found.length, 1)
})

test('stripping preserves line numbers', () => {
  // Blanked rather than removed, so anything that later reports a line still
  // reports the right one.
  const src = ['/* a', 'b', 'c */', `require("x")`, ''].join('\n')
  assert.strictEqual(stripCommentsAndTemplates(src).split('\n').length, src.split('\n').length)
})