Module-Rust/client/test/build.test.js

// What can be checked about the client half without a browser.
//
// Not much, and being honest about that is the point: the client half's real
// failures are timing and resolution, and neither has a shape a DOM-less test
// runner can see. MODULE_API.md §7.7's four-step browser smoke is what actually
// proves this half works, and it is re-run whenever this seam changes.
//
// What IS testable here is the configuration that decides resolution — and one
// of these tests exists because the trap it guards cost this project real time: Vite's object-form `resolve.alias` does PREFIX matching, so a `react`
// key silently also rewrites `react/jsx-runtime`. An anchored regexp in the
// array form cannot. That is a property of the config, and a test can hold it.

import test from 'node:test'
import assert from 'node:assert'
import fs from 'node:fs'
import path from 'node:path'
import { fileURLToPath } from 'node:url'

const HERE = path.dirname(fileURLToPath(import.meta.url))
const CLIENT = path.resolve(HERE, '..')

const { bareImports, problemsWith } = await import('../scripts/checkExternals.js')
const configModule = await import('../vite.config.js')
const config = configModule.default
const { SHARED, SHARED_PACKAGES: guardedPackages } = configModule

test('every alias is an anchored regexp, never a bare prefix string', () => {
  const aliases = config.resolve.alias
  assert.ok(Array.isArray(aliases), 'alias must use the ARRAY form — the object form prefix-matches')
  for (const { find } of aliases) {
    assert.ok(find instanceof RegExp, `alias "${find}" is a string; a string prefix-matches`)
    assert.ok(find.source.startsWith('^') && find.source.endsWith('$'), `alias ${find} is not anchored`)
  }
})

test('react and react/jsx-runtime resolve to different shims', () => {
  // The exact collision the object form causes. Asserted on the outcome rather
  // than on the config's shape, so it keeps holding however the config is
  // rewritten.
  const resolve = (specifier) =>
    config.resolve.alias.find(({ find }) => find.test(specifier))?.replacement
  assert.ok(resolve('react'))
  assert.ok(resolve('react/jsx-runtime'))
  assert.notStrictEqual(resolve('react'), resolve('react/jsx-runtime'))
})

test('every shared dependency is aliased', () => {
  for (const specifier of ['react', 'react/jsx-runtime', 'react-dom', 'react-dom/client', 'react-router-dom']) {
    assert.ok(
      config.resolve.alias.some(({ find }) => find.test(specifier)),
      `${specifier} is not aliased — it would be bundled, giving the page a second copy`,
    )
  }
})

test('rollup external stays empty — it preempts the aliases rather than backing them up', () => {
  // Rollup asks `external` BEFORE Vite's alias resolver runs, so a specifier
  // listed in both is marked external and never aliased. The chunk then ships
  // bare `import 'react'`, which no browser can resolve without an import map
  // and CSP forbids one. §3.6 shows both; they do not compose.
  assert.deepStrictEqual(config.build.rollupOptions.external, [])
})

test('the not-bundled guard covers every shared specifier and is not derived from them', () => {
  // The direction of this dependency is the finding. Deriving the forbidden
  // package list FROM the alias list means deleting an alias also deletes the
  // guard against what that alias prevented — which is precisely when the guard
  // is needed. So the guard states the contract, and this asserts the aliases
  // stay inside it.
  const packages = new Set(guardedPackages)
  for (const { specifier } of SHARED) {
    const pkg = specifier.startsWith('@') ? specifier.split('/').slice(0, 2).join('/') : specifier.split('/')[0]
    assert.ok(packages.has(pkg), `${pkg} is aliased but not guarded against being bundled`)
  }
})

test('every alias points at a shim file that exists', () => {
  for (const { find, replacement } of config.resolve.alias) {
    assert.ok(fs.existsSync(replacement), `alias ${find} points at a missing file: ${replacement}`)
  }
})

test('the build emits one unhashed entry.js, which is what module.json names', () => {
  assert.deepStrictEqual(config.build.lib.formats, ['es'])
  assert.strictEqual(config.build.lib.fileName(), 'entry.js')
  const manifest = JSON.parse(fs.readFileSync(path.resolve(CLIENT, '..', 'module.json'), 'utf8'))
  assert.strictEqual(manifest.client.entry, 'client/dist/entry.js')
  assert.strictEqual(config.build.outDir, 'dist')
})

test('modulePreload polyfilling stays off — an inline bootstrap is refused under CSP', () => {
  assert.strictEqual(config.build.modulePreload.polyfill, false)
})

test('exactly one file reads window.__rg, and every shim goes through it', () => {
  // `shim/rg.js` is the single reader, and that is not tidiness: it is what
  // makes the "core did not publish its dependencies" message reachable. The
  // shims touch the global before anything else in the chunk does, so a check
  // placed in the first-imported file is a guarantee that lasts until someone
  // sorts the imports.
  const dir = path.join(CLIENT, 'src', 'shim')
  const shims = fs.readdirSync(dir)
  assert.ok(shims.length >= 5)
  for (const file of shims) {
    const source = fs.readFileSync(path.join(dir, file), 'utf8')
    const code = source.replace(/^\s*\/\/.*$/gm, '') // the comments discuss the global
    if (file === 'rg.js') {
      assert.match(code, /window\.__rg/, 'rg.js must be the one that reads the global')
      assert.doesNotMatch(code, /^\s*import\s/m, 'rg.js imports something')
      continue
    }
    assert.doesNotMatch(code, /window\.__rg/, `${file} reads the global directly instead of via rg()`)
    assert.match(code, /rg\(\)/, `${file} does not resolve through rg()`)
    // A shim may import its sibling helper and nothing else — anything further
    // would be a shim with a dependency to resolve, the problem it exists to remove.
    for (const [, spec] of code.matchAll(/^\s*import\s[^'"]*['"]([^'"]+)['"]/gm)) {
      assert.strictEqual(spec, './rg.js', `${file} imports ${spec}`)
    }
  }
})

test('the built chunk has no bare imports and bundles no shared dependency', () => {
  // The artifact check itself, over the artifact that ships. Skipped rather than
  // failed when there is no build: `npm test` must be runnable before `npm run
  // build`, and CI runs them in order.
  const chunk = path.join(CLIENT, 'dist', 'entry.js')
  if (!fs.existsSync(chunk)) return
  assert.deepStrictEqual(problemsWith(fs.readFileSync(chunk, 'utf8')), [])
})

test('an import inside a string is not an import — the check reads code, not text', () => {
  // The regression that made this necessary: the first chunk with real content
  // in it had a button labelled "Approve and import" put the token
  // immediately before a quote. The check rejected the whole build, naming a
  // fragment of minified JSX as the offending specifier.
  const uiCopy = 'const a=n("button",{children:"Approve and import"}),b=1;'
  assert.deepStrictEqual(bareImports(uiCopy), [])

  // Neither is one in a comment, or in a template literal.
  assert.deepStrictEqual(bareImports('// import "react" would be wrong here\nconst a=1'), [])
  assert.deepStrictEqual(bareImports('/* import "react" */ const a=1'), [])
  assert.deepStrictEqual(bareImports('const s=`import "react"`'), [])

  // And a real one still is, in each form the build could emit.
  assert.deepStrictEqual(bareImports('import"react";'), ['react'])
  assert.deepStrictEqual(bareImports('import{useState}from"react";'), ['react'])
  assert.deepStrictEqual(bareImports('const m=await import("react-dom/client")'), ['react-dom/client'])
  // A relative specifier is a split chunk, not a shared dependency: not our concern.
  assert.deepStrictEqual(bareImports('import"./other.js";'), [])

  // The case that proves the mask tracks escapes: a quote escaped INSIDE a
  // string must not end it early and leave the tail looking like code.
  assert.deepStrictEqual(bareImports('const s="he said \\"import\\" loudly";'), [])
})