fix: Fallback to parentLoad if parsing fails (#104)

Closes #101

hook.js

@@ -264,14 +264,16 @@ function createHook (meta) {
   async function getSource (url, context, parentGetSource) {
     if (hasIitm(url)) {
       const realUrl = deleteIitm(url)
-      const setters = await processModule({
-        srcUrl: realUrl,
-        context,
-        parentGetSource,
-        parentResolve: cachedResolve
-      })
-      return {
-        source: `
+
+      try {
+        const setters = await processModule({
+          srcUrl: realUrl,
+          context,
+          parentGetSource,
+          parentResolve: cachedResolve
+        })
+        return {
+          source: `
 import { register } from '${iitmURL}'
 import * as namespace from ${JSON.stringify(realUrl)}
 
@@ -286,6 +288,25 @@ ${Array.from(setters.values()).join('\n')}
 
 register(${JSON.stringify(realUrl)}, _, set, ${JSON.stringify(specifiers.get(realUrl))})
 `
+        }
+      } catch (cause) {
+        // If there are other ESM loader hooks registered as well as iitm,
+        // depending on the order they are registered, source might not be
+        // JavaScript.
+        //
+        // If we fail to parse a module for exports, we should fall back to the
+        // parent loader. These modules will not be wrapped with proxies and
+        // cannot be Hook'ed but at least this does not take down the entire app
+        // and block iitm from being used.
+        //
+        // We log the error because there might be bugs in iitm and without this
+        // it would be very tricky to debug
+        const err = new Error(`'import-in-the-middle' failed to wrap '${realUrl}'`)
+        err.cause = cause
+        console.warn(err)
+
+        // Revert back to the non-iitm URL
+        url = realUrl
       }
     }
 

test/fixtures/json-attributes.mjs

@@ -0,0 +1,5 @@
+import coolFile from './something.json' with { type: 'json' }
+
+export default {
+  data: coolFile.data
+}

test/hook/v20.10-static-import-attributes.mjs

@@ -0,0 +1,17 @@
+// Unless explicitly stated otherwise all files in this repository are licensed under the Apache 2.0 License.
+//
+// This product includes software developed at Datadog (https://www.datadoghq.com/). Copyright 2021 Datadog, Inc.
+
+import jsonMjs from '../fixtures/json-attributes.mjs'
+import { strictEqual } from 'assert'
+
+// Acorn does not support import attributes so an error is logged but the import
+// still works!
+//
+// Hook((exports, name) => {
+//   if (name.match(/json\.mjs/)) {
+//     exports.default.data += '-dawg'
+//   }
+// })
+
+strictEqual(jsonMjs.data, 'dog')

test/other/v20.10-import-executable.mjs

@@ -0,0 +1,8 @@
+// Unless explicitly stated otherwise all files in this repository are licensed under the Apache 2.0 License.
+//
+// This product includes software developed at Datadog (https://www.datadoghq.com/). Copyright 2021 Datadog, Inc.
+
+(async () => {
+  const lib = await import('../fixtures/executable')
+  console.assert(lib)
+})()