feat: add ESM support when bundling with NFT

src/runtimes/node/bundlers/nft/index.ts

@@ -3,50 +3,98 @@ import { dirname, normalize, resolve } from 'path'
 import { nodeFileTrace } from '@vercel/nft'
 
 import type { BundleFunction } from '..'
+import type { FunctionConfig } from '../../../../config'
+import { cachedReadFile, FsCache, safeUnlink } from '../../../../utils/fs'
 import type { GetSrcFilesFunction } from '../../../runtime'
 import { getBasePath } from '../../utils/base_path'
 import { filterExcludedPaths, getPathsOfIncludedFiles } from '../../utils/included_files'
 
-const bundle: BundleFunction = async ({
-  basePath,
-  config,
-  extension,
-  featureFlags,
-  filename,
-  mainFile,
-  name,
-  pluginsModulesPath,
-  repositoryRoot = basePath,
-  runtime,
-  srcDir,
-  srcPath,
-  stat,
-}) => {
-  const srcFiles = await getSrcFiles({
+import { transpileMany } from './transpile'
+import type { Cache } from './types'
+
+const bundle: BundleFunction = async ({ basePath, config, mainFile, repositoryRoot = basePath }) => {
+  const { includedFiles = [], includedFilesBasePath } = config
+  const { exclude: excludedPaths, paths: includedFilePaths } = await getPathsOfIncludedFiles(
+    includedFiles,
+    includedFilesBasePath || basePath,
+  )
+  const {
+    cleanupFunction,
+    paths: dependencyPaths,
+    transpilation,
+  } = await traceFilesAndTranspile({
     basePath: repositoryRoot,
-    config: {
-      ...config,
-      includedFilesBasePath: config.includedFilesBasePath || basePath,
-    },
-    extension,
-    featureFlags,
-    filename,
+    config,
     mainFile,
-    name,
-    pluginsModulesPath,
-    repositoryRoot,
-    runtime,
-    srcDir,
-    srcPath,
-    stat,
   })
-  const dirnames = srcFiles.map((filePath) => normalize(dirname(filePath))).sort()
+  const filteredIncludedPaths = filterExcludedPaths([...dependencyPaths, ...includedFilePaths], excludedPaths)
+  const dirnames = filteredIncludedPaths.map((filePath) => normalize(dirname(filePath))).sort()
 
   return {
+    aliases: transpilation,
     basePath: getBasePath(dirnames),
-    inputs: srcFiles,
+    cleanupFunction,
+    inputs: dependencyPaths,
     mainFile,
-    srcFiles,
+    srcFiles: [...filteredIncludedPaths, ...transpilation.keys()],
+  }
+}
+
+const traceFilesAndTranspile = async function ({
+  basePath,
+  config,
+  mainFile,
+}: {
+  basePath?: string
+  config: FunctionConfig
+  mainFile: string
+}) {
+  const fsCache: FsCache = {}
+  const cache: Cache = {}
+  const { fileList: dependencyPaths } = await nodeFileTrace([mainFile], {
+    base: basePath,
+    cache,
+    readFile: async (path: string) => {
+      try {
+        const source = (await cachedReadFile(fsCache, path, 'utf8')) as string
+
+        return source
+      } catch (error) {
+        if (error.code === 'ENOENT' || error.code === 'EISDIR') {
+          return null
+        }
+
+        throw error
+      }
+    },
+  })
+  const normalizedDependencyPaths = dependencyPaths.map((path) => (basePath ? resolve(basePath, path) : resolve(path)))
+
+  // We look at the cache object to find any paths corresponding to ESM files.
+  const esmPaths = [...(cache.analysisCache?.entries() || [])].filter(([, { isESM }]) => isESM).map(([path]) => path)
+
+  // After transpiling the ESM files, we get back a `Map` mapping the path of
+  // each transpiled to its original path.
+  const transpilation = await transpileMany(esmPaths, config)
+
+  // Creating a `Set` with the original paths of the transpiled files so that
+  // we can do a O(1) lookup.
+  const originalPaths = new Set(transpilation.values())
+
+  // We remove the transpiled paths from the list of traced files, otherwise we
+  // would end up with duplicate files in the archive.
+  const filteredDependencyPaths = normalizedDependencyPaths.filter((path) => !originalPaths.has(path))
+
+  // The cleanup function will delete all the temporary files that were created
+  // as part of the transpilation process.
+  const cleanupFunction = async () => {
+    await Promise.all([...transpilation.keys()].map(safeUnlink))
+  }
+
+  return {
+    cleanupFunction,
+    paths: filteredDependencyPaths,
+    transpilation,
   }
 }
 

src/runtimes/node/bundlers/nft/transpile.ts

@@ -0,0 +1,46 @@
+import { build } from '@netlify/esbuild'
+import { tmpName } from 'tmp-promise'
+
+import type { FunctionConfig } from '../../../../config'
+import { safeUnlink } from '../../../../utils/fs'
+import { getBundlerTarget } from '../esbuild/bundler_target'
+
+const transpile = async (path: string, config: FunctionConfig) => {
+  const targetPath = await tmpName({ postfix: '.js' })
+  const cleanupFn = () => safeUnlink(targetPath)
+
+  // The version of ECMAScript to use as the build target. This will determine
+  // whether certain features are transpiled down or left untransformed.
+  const nodeTarget = getBundlerTarget(config.nodeVersion)
+
+  await build({
+    bundle: false,
+    entryPoints: [path],
+    format: 'cjs',
+    logLevel: 'error',
+    outfile: targetPath,
+    platform: 'node',
+    target: [nodeTarget],
+  })
+
+  return {
+    cleanupFn,
+    path: targetPath,
+  }
+}
+
+const transpileMany = async (paths: string[], config: FunctionConfig) => {
+  const transpiledPaths: Map<string, string> = new Map()
+
+  await Promise.all(
+    paths.map(async (path) => {
+      const transpiled = await transpile(path, config)
+
+      transpiledPaths.set(transpiled.path, path)
+    }),
+  )
+
+  return transpiledPaths
+}
+
+export { transpileMany }

src/runtimes/node/bundlers/nft/types.ts

@@ -0,0 +1,6 @@
+interface Cache {
+  analysisCache?: Map<string, { isESM: boolean; [key: string]: unknown }>
+  [key: string]: unknown
+}
+
+export { Cache }

tests/main.js

@@ -398,7 +398,7 @@ testMany(
 
 testMany(
   'Can bundle functions with `.js` extension using ES Modules and feature flag ON',
-  ['bundler_esbuild', 'bundler_default', 'todo:bundler_nft'],
+  ['bundler_esbuild', 'bundler_default', 'bundler_nft'],
   async (options, t) => {
     const opts = merge(options, { featureFlags: { defaultEsModulesToEsbuild: true } })
 
@@ -411,7 +411,7 @@ testMany(
 
 testMany(
   'Can bundle functions with `.js` extension using ES Modules and feature flag OFF',
-  ['bundler_esbuild', 'bundler_default', 'todo:bundler_nft'],
+  ['bundler_esbuild', 'bundler_default', 'bundler_nft'],
   async (options, t) => {
     const bundler = options.config['*'].nodeBundler
 
@@ -1206,7 +1206,7 @@ testMany(
 
 testMany(
   'Handles a JavaScript function ({name}.mjs, {name}/{name}.mjs, {name}/index.mjs)',
-  ['bundler_esbuild', 'bundler_default', 'todo:bundler_nft'],
+  ['bundler_esbuild', 'bundler_default'],
   async (options, t) => {
     const { files, tmpDir } = await zipFixture(t, 'node-mjs', {
       length: 3,