send origin server errors back to the frontend

Author: Bart Veneman

api/v2/_extract-css-basic.js

@@ -80,8 +80,26 @@ export function getStyles(nodes) {
   return items
 }
 
+export class HttpError extends Error {
+  constructor({ url, statusCode, statusText }) {
+    this.url = url
+    this.statusCode = statusCode
+    this.statusText = statusText
+    this.message = `The origin server at "${url}" errored with status ${statusCode} (${statusText})`
+  }
+}
+
 export async function extractCss(url) {
-  var { body, headers } = await got(url)
+  let body = ''
+  let headers = {}
+
+  try {
+    var response = await got(url)
+    body = response.body
+    headers = response.headers
+  } catch (error) {
+    throw new HttpError({ url, statusCode, statusText })
+  }
 
   // Return early if our response was a CSS file already
   if (headers['content-type'].includes('text/css')) {
@@ -117,7 +135,11 @@ export async function extractCss(url) {
       // And c'mon, don't @import inside your @import.
       var importUrls = getImportUrls(item.css)
       if (importUrls.length > 0) {
-        var cssRequests = importUrls.map(importUrl => getCssFile(resolveUrl(importUrl, url)))
+        var cssRequests = importUrls.map(
+          importUrl => getCssFile(resolveUrl(importUrl, url))
+            // silently fail on sub-resources
+            .catch(_ => '')
+        )
         var importedFiles = await Promise.all(cssRequests)
         importedFiles.map((css, index) => {
           result.push({

api/v2/extract-css.js

@@ -1,5 +1,5 @@
 import { isUrl } from '../_is-url.js'
-import { extractCss } from './_extract-css-basic.js'
+import { extractCss, HttpError } from './_extract-css-basic.js'
 
 export default async (req, res) => {
   const { url } = req.query
@@ -26,6 +26,15 @@ export default async (req, res) => {
     const css = result.map(({ css }) => css).join('\n')
     return res.end(css)
   } catch (error) {
+    if (error instanceof HttpError) {
+      res.statusCode = error.statusCode
+      return res.json({
+        url,
+        statusCode: error.statusCode,
+        statusText: error.statusText,
+        message: error.message,
+      })
+    }
     res.statusCode = 500
     return res.json({ message: error.message })
   }