feat: use esbuild by default for es modules, if detected

package.json

@@ -63,6 +63,7 @@
     "del": "^6.0.0",
     "elf-cam": "^0.1.1",
     "end-of-stream": "^1.4.4",
+    "es-module-lexer": "^0.7.1",
     "execa": "^5.0.0",
     "filter-obj": "^2.0.1",
     "find-up": "^5.0.0",

src/runtimes/node/detect_es_module.js

@@ -0,0 +1,22 @@
+const fs = require('fs')
+
+const { init, parse } = require('es-module-lexer')
+
+const detectEsModule = async ({ srcFile }) => {
+  // console.log('srcFile: ', srcFile)
+  if (!srcFile) {
+    return false
+  }
+
+  await init
+
+  // Would love to just use await fs.promises.readFile, but it's not available in our version of Node.
+  // eslint-disable-next-line node/no-sync
+  const srcFileContents = fs.readFileSync(srcFile, { encoding: 'utf8' })
+
+  const [imports, exports] = parse(srcFileContents)
+
+  return imports.length !== 0 && exports.length !== 0
+}
+
+module.exports = { detectEsModule }

src/runtimes/node/index.js

@@ -4,14 +4,29 @@ const cpFile = require('cp-file')
 
 const { JS_BUNDLER_ESBUILD, JS_BUNDLER_ESBUILD_ZISI, JS_BUNDLER_ZISI, RUNTIME_JS } = require('../../utils/consts')
 
+const { detectEsModule } = require('./detect_es_module')
 const { findFunctionsInPaths } = require('./finder')
 const { getSrcFiles } = require('./src_files')
 const { zipEsbuild } = require('./zip_esbuild')
 const { zipZisi } = require('./zip_zisi')
 
 // We use ZISI as the default bundler until the next major release, with the
 // exception of TypeScript files, for which the only option is esbuild.
-const getDefaultBundler = ({ extension }) => (extension === '.ts' ? JS_BUNDLER_ESBUILD : JS_BUNDLER_ZISI)
+const getDefaultBundler = ({ extension, srcFile }) => {
+  if (extension === '.ts') {
+    return JS_BUNDLER_ESBUILD
+  }
+
+  if (srcFile) {
+    const isEsModule = detectEsModule({ srcFile })
+
+    if (isEsModule) {
+      return JS_BUNDLER_ESBUILD
+    }
+  }
+
+  return JS_BUNDLER_ZISI
+}
 
 // A proxy for the `getSrcFiles` function which adds a default `bundler` using
 // the `getDefaultBundler` function.
@@ -35,7 +50,8 @@ const zipFunction = async function ({
   srcPath,
   stat,
 }) {
-  const bundler = config.nodeBundler || getDefaultBundler({ extension })
+  // how do you construct the srcFile?
+  const bundler = config.nodeBundler || getDefaultBundler({ extension, srcFile: join(srcPath, filename) })
 
   // If the file is a zip, we assume the function is bundled and ready to go.
   // We simply copy it to the destination path with no further processing.

tests/main.js

@@ -282,6 +282,10 @@ testBundlers('Can require local files', [ESBUILD, ESBUILD_ZISI, DEFAULT], async
   await zipNode(t, 'local-require', { opts: { config: { '*': { nodeBundler: bundler } } } })
 })
 
+testBundlers('Can require local esm files', [ESBUILD, ESBUILD_ZISI, DEFAULT], async (bundler, t) => {
+  await zipNode(t, 'local-require-esm', { opts: { config: { '*': { nodeBundler: bundler } } } })
+})
+
 testBundlers('Can require local files deeply', [ESBUILD, ESBUILD_ZISI, DEFAULT], async (bundler, t) => {
   await zipNode(t, 'local-deep-require', { opts: { config: { '*': { nodeBundler: bundler } } } })
 })