From fc06c9ac048c8f411cabbb5b89f19e671e0f05b8 Mon Sep 17 00:00:00 2001
From: Mike Bland <mbland@acm.org>
Date: Fri, 5 Jan 2024 12:17:51 -0500
Subject: [PATCH] Rethrow Jsdom import errors properly

Based on advice from:

- https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Error/Error#rethrowing_an_error_with_a_cause

The Error object is now much more informative and useful, and the test
performs specific assertions on each nested Error.
---
 lib/jsdom.js       |  4 ++--
 test/jsdom.test.js | 10 +++++++---
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/lib/jsdom.js b/lib/jsdom.js
index cb5444b..6fff548 100644
--- a/lib/jsdom.js
+++ b/lib/jsdom.js
@@ -71,7 +71,7 @@ export default class JsdomPageOpener {
     try {
       await this.#importModules(window, document)
     } catch (err) {
-      throw new Error(`error importing modules from ${pagePath}: ${err}`)
+      throw new Error(`opening ${pagePath}`, { cause: err })
     }
     return { window, document, close() { window.close() } }
   }
@@ -159,6 +159,6 @@ function importModules(doc) {
   const modules = Array.from(doc.querySelectorAll('script[type="module"]'))
   return Promise.all(modules.filter(m => m.src).map(async m => {
     try { await import(m.src) }
-    catch (err) { throw new Error(`error importing ${m.src}: ${err}`) }
+    catch (err) { throw new Error(`importing ${m.src}`, { cause: err }) }
   }))
 }
diff --git a/test/jsdom.test.js b/test/jsdom.test.js
index 9c42691..1bfe8fd 100644
--- a/test/jsdom.test.js
+++ b/test/jsdom.test.js
@@ -17,8 +17,12 @@ describe.skipIf(globalThis.window !== undefined)('JsdomPageOpener', () => {
     const pagePath = './test-modules/error.html'
     const moduleUrl = pathToFileURL('./test-modules/error.js')
 
-    await expect(() => opener.open('unused', pagePath)).rejects
-      .toThrowError(`error importing modules from ${pagePath}: ` +
-        `Error: error importing ${moduleUrl.href}: Error: test error`)
+    const result = opener.open('unused', pagePath)
+
+    await expect(result).rejects.toThrowError(`opening ${pagePath}`)
+    await result.catch(err => {
+      expect(err.cause.message).toBe(`importing ${moduleUrl.href}`)
+      expect(err.cause.cause.message).toBe('test error')
+    })
   })
 })