Return 500 status when asset upload error page is rendered

Author: jamesmengo

.changeset/bright-impalas-float.md

@@ -2,4 +2,4 @@
 '@shopify/theme': minor
 ---
 
-Render error overlay when `theme dev` encounters asset upload errors
+Render error overlay when `theme dev` encounters asset upload errors. A 500 status code is returned when the error overlay is rendered.

packages/theme/src/cli/utilities/theme-environment/html.ts

@@ -33,6 +33,8 @@ export function getHtmlHandler(theme: Theme, ctx: DevServerContext) {
         assertThemeId(response, html, String(theme.id))
 
         if (ctx.options.errorOverlay !== 'silent' && ctx.localThemeFileSystem.uploadErrors.size > 0) {
+          setResponseStatus(event, 500, 'Failed to Upload Theme Files')
+          setResponseHeader(event, 'Content-Type', 'text/html')
           html = getErrorPage({
             title: 'Failed to Upload Theme Files',
             header: 'Upload Errors',