test(sw): shared Playwright runtime resolver

packages/sw/tests/playwright-runtime.mjs

@@ -0,0 +1,76 @@
+// Playwright (and the image helpers pngjs / pixelmatch) for the SW browser tests. Playwright is not a repository
+// dependency, so the first location that has it is used:
+//   1. SW_PLAYWRIGHT_PATH   the playwright package directory (or its entry file)
+//   2. SW_RUNTIME_MODULES   a node_modules directory that contains playwright
+//   3. HM_PLAYWRIGHT_DIR    a project directory whose node_modules contains playwright (scripts/verify-quality-runtime.mjs)
+//   4. this repository      node_modules/playwright (npm i -D playwright, not committed)
+//   5. the Codex runtime    <home>/.cache/codex-runtimes/codex-primary-runtime/dependencies/node/node_modules
+//   6. global npm           `npm root -g`
+// A location set by an environment variable must exist: a wrong value fails instead of falling back silently.
+import { createRequire } from 'node:module'
+import { execFileSync } from 'node:child_process'
+import { existsSync } from 'node:fs'
+import os from 'node:os'
+import path from 'node:path'
+
+const nodeModulesOf = file => {
+  const parts = path.resolve(file).split(path.sep)
+  const index = parts.lastIndexOf('node_modules')
+  return index < 0 ? null : parts.slice(0, index + 1).join(path.sep)
+}
+const fromNodeModules = dir => createRequire(path.join(dir, 'index.js'))
+const globalRoot = () => {
+  try { return execFileSync('npm', ['root', '-g'], { encoding: 'utf8', shell: process.platform === 'win32', stdio: ['ignore', 'pipe', 'ignore'] }).trim() } catch { return null }
+}
+
+function candidates() {
+  const list = []
+  const { SW_PLAYWRIGHT_PATH: entry, SW_RUNTIME_MODULES: modules, HM_PLAYWRIGHT_DIR: project } = process.env
+  if (entry) {
+    const modulesDir = nodeModulesOf(entry)
+    list.push({ source: `SW_PLAYWRIGHT_PATH=${entry}`, explicit: true, entry: path.resolve(entry), require: modulesDir ? fromNodeModules(modulesDir) : createRequire(import.meta.url) })
+  }
+  if (modules) list.push({ source: `SW_RUNTIME_MODULES=${modules}`, explicit: true, require: fromNodeModules(path.resolve(modules)) })
+  if (project) list.push({ source: `HM_PLAYWRIGHT_DIR=${project}`, explicit: true, require: createRequire(path.join(path.resolve(project), 'package.json')) })
+  list.push({ source: 'repository node_modules', require: createRequire(import.meta.url) })
+  const codex = path.join(os.homedir(), '.cache', 'codex-runtimes', 'codex-primary-runtime', 'dependencies', 'node', 'node_modules')
+  if (existsSync(codex)) list.push({ source: `Codex runtime ${codex}`, require: fromNodeModules(codex) })
+  const global = globalRoot()
+  if (global && existsSync(global)) list.push({ source: `global npm ${global}`, require: fromNodeModules(global) })
+  return list
+}
+
+let resolved
+function resolve() {
+  if (resolved) return resolved
+  const tried = []
+  for (const candidate of candidates()) {
+    try {
+      const entry = candidate.entry ?? candidate.require.resolve('playwright')
+      if (candidate.entry && !existsSync(candidate.entry)) throw new Error('path does not exist')
+      resolved = { ...candidate, entry }
+      return resolved
+    } catch (error) {
+      tried.push(`${candidate.source}: ${error.message.split('\n')[0]}`)
+      if (candidate.explicit) break
+    }
+  }
+  throw new Error(`Playwright not found for the SW browser tests. Set SW_RUNTIME_MODULES to a node_modules directory that contains playwright (or SW_PLAYWRIGHT_PATH to the playwright package).\n  tried:\n  - ${tried.join('\n  - ')}`)
+}
+
+/** The playwright module (`{ chromium, firefox, ... }`). */
+export const loadPlaywright = () => resolve().require(resolve().entry)
+
+/**
+ * A `require` rooted where Playwright was found, for the other runtime modules the tests use (pngjs, pixelmatch).
+ * `require('playwright')` through it returns the same module as `loadPlaywright()`.
+ */
+export function runtimeRequire() {
+  const { require, entry } = resolve()
+  const wrapped = id => (id === 'playwright' ? require(entry) : require(id))
+  wrapped.resolve = (id, options) => (id === 'playwright' ? entry : require.resolve(id, options))
+  return wrapped
+}
+
+/** Where Playwright came from (for reports). */
+export const playwrightSource = () => resolve().source