Jetpack Custom CSS error message broken in AMP

[schlessera]

Bug Description

The Jetpack Custom CSS feature seems broken in some way in AMP.

When I look at the validation errors of a page that uses this feature, I see the following error:

Note the error type, and the fact that it failed to download the custom CSS in the first place.

However, when I try this URL directly, I get the correct stylesheet data:

I think the error message here is conflicting, as the description is shown for styling, but the actual problem is that the file could not be downloaded.

On an empty site, the custom CSS loading works, and there's no validation error at all.

Expected Behaviour

The AMP validation error should not fail to download and show an HTTP error, but rather show a style-related error.

Steps to reproduce

I haven't been able to pinpoint this exactly but wanted to keep a reference to it for now.

Additional context

wp-core

version: 5.3
site_language: en_US
user_language: en_US
timezone: Europe/Berlin
permalink: /%postname%/
https_status: true
user_registration: 0
default_comment_status: open
multisite: false
user_count: 20
dotorg_communication: true

wp-paths-sizes

wordpress_path: /Users/alain/Sites/alainschlesser
wordpress_size: 91.44 MB (95877222 bytes)
uploads_path: /Users/alain/Sites/alainschlesser/wp-content/uploads
uploads_size: 143.56 MB (150536695 bytes)
themes_path: /Users/alain/Sites/alainschlesser/wp-content/themes
themes_size: 15.44 MB (16193011 bytes)
plugins_path: /Users/alain/Sites/alainschlesser/wp-content/plugins
plugins_size: 138.34 MB (145059888 bytes)
database_size: 16.41 MB (17203200 bytes)
total_size: 405.19 MB (424870016 bytes)

wp-dropins (1)

advanced-cache.php: true

wp-active-theme

name: Beaver Builder Child Theme (bb-theme-child)
version: 1.0
author: The Beaver Builder Team
author_website: http://www.fastlinemedia.com
parent_theme: Beaver Builder Theme (bb-theme)
theme_features: automatic-feed-links, title-tag, post-thumbnails, woocommerce, menus, wc-product-gallery-zoom, wc-product-gallery-lightbox, wc-product-gallery-slider, amp, widgets
theme_path: /Users/alain/Sites/alainschlesser/wp-content/themes/bb-theme-child

wp-parent-theme

name: Beaver Builder Theme (bb-theme)
version: 1.6 (latest version: 1.7.4.1)
author: The Beaver Builder Team
author_website: http://www.wpbeaverbuilder.com/?utm_medium=bb-pro&utm_source=bb-theme&utm_campaign=themes-admin-page
theme_path: /Users/alain/Sites/alainschlesser/wp-content/themes/bb-theme

wp-themes-inactive (6)

Make: version: 1.9.25, author: The Theme Foundry
Twenty Fifteen: version: 2.5, author: the WordPress team
Twenty Nineteen: version: 1.4, author: the WordPress team
Twenty Seventeen: version: 2.2, author: the WordPress team
Twenty Sixteen: version: 2.0, author: the WordPress team
Twenty Twenty: version: 1.0, author: the WordPress team

wp-mu-plugins (2)

Force Strong Passwords - WPE Edition: version: 1.6.4, author: Jason Cosper
Stop long comments: version: 0.0.4, author: WPEngine

wp-plugins-active (25)

AlainSchlesser.com Speaking Page Plugin.: version: 0.2.13, author: Alain Schlesser alain.schlesser@gmail.com
AMP: version: 1.4.1, author: AMP Project Contributors
Antispam Bee: version: 2.9.1, author: pluginkollektiv
Beaver Builder Plugin (Pro Version): version: 1.10.4, author: The Beaver Builder Team (latest version: 2.2.6.3)
Better Click To Tweet: version: 5.9.1, author: Ben Meredith
Crowd Control by Postmatic: version: 1.1, author: Ronald Huereca, Jason Lemieux
Enable Media Replace: version: 3.3.7, author: ShortPixel
FontAwesome.io ShortCodes: version: 1.0, author: Alexander Weleczka
Google Tag Manager for Wordpress: version: 1.11.2, author: Thomas Geiger
Hustle: version: 5.0.1.2, author: WPMU DEV
Jetpack by WordPress.com: version: 5.6.2, author: Automattic (latest version: 7.9.1)
PHP Compatibility Checker: version: 1.5.0, author: WP Engine
Postmatic & Postmatic Labs: version: 2.1.6, author: Postmatic
Regenerate Thumbnails: version: 3.1.2, author: Alex Mills (Viper007Bond)
Remote Content: version: 2.0.0, author: Nick Davis
Responsive Lightbox: version: 1.3.2, author: subhansanjaya
Rewrite Rules Inspector: version: 1.2.1, author: Daniel Bachhuber, Automattic
Smush Pro: version: 3.3.2, author: WPMU DEV
SVG Support: version: 2.3.15, author: Benbodhi
SyntaxHighlighter Evolved: version: 3.5.1, author: Alex Mills (Viper007Bond)
SyntaxHighlighter Evolved - Spacegray: version: 1.0.2, author: Manoz
Vocalizer: author: Alain Schlesser, version: (undefined)
WPMU DEV Dashboard: version: 4.7.3.5, author: WPMU DEV
Yoast SEO: version: 12.6.2, author: Team Yoast

wp-plugins-inactive (14)

Akismet Anti-Spam: version: 4.1.3, author: Automattic
Autoptimize: version: 2.5.1, author: Frank Goossens (futtta)
Defender Pro: version: 2.2.3, author: WPMU DEV
Duplicate Post: version: 3.2.3, author: Enrico Battocchi
Exploit Scanner: version: 1.5.2, author: Automattic
GitHub Updater: version: 6.3.1.1, author: Andy Fragen
Hummingbird Pro: version: 2.2.2, author: WPMU DEV
Query Monitor: version: 3.5.0, author: John Blackbourn
Ultimate Addon for Beaver Builder: version: 1.4.1, author: Brainstorm Force
UpdraftPlus - Backup/Restore: version: 2.12.40.21, author: UpdraftPlus.Com, DavidAnderson
WP Rocket: version: 2.9.11, author: WP Media
WP Sync DB: version: 1.5, author: Sean Lang
WP Sync DB Media Files: version: 1.1.4b1, author: Sean Lang

wp-media

image_editor: WP_Image_Editor_GD
imagick_module_version: Not available
imagemagick_version: Not available
gd_version: bundled (2.1.0 compatible)
ghostscript_version: 9.50

wp-server

server_architecture: Darwin 18.7.0 x86_64
httpd_software: nginx/1.17.3
php_version: 7.2.24 64bit
php_sapi: fpm-fcgi
max_input_variables: 3000
time_limit: 300
memory_limit: 2G
max_input_time: 60
upload_max_size: 128M
php_post_max_size: 128M
curl_version: 7.67.0 OpenSSL/1.1.1d
suhosin: false
imagick_availability: false
htaccess_extra_rules: true

wp-database

extension: mysqli
server_version: 10.4.10-MariaDB
client_version: mysqlnd 5.0.12-dev - 20150407 - $Id: 3591daad22de08524295e1bd073aceeff11e6579 $

wp-constants

WP_HOME: undefined
WP_SITEURL: undefined
WP_CONTENT_DIR: /Users/alain/Sites/alainschlesser/wp-content
WP_PLUGIN_DIR: /Users/alain/Sites/alainschlesser/wp-content/plugins
WP_MAX_MEMORY_LIMIT: 2G
WP_DEBUG: true
WP_DEBUG_DISPLAY: false
WP_DEBUG_LOG: false
SCRIPT_DEBUG: true
WP_CACHE: true
CONCATENATE_SCRIPTS: undefined
COMPRESS_SCRIPTS: undefined
COMPRESS_CSS: undefined
WP_LOCAL_DEV: undefined
DB_CHARSET: utf8
DB_COLLATE: utf8_unicode_ci

wp-filesystem

wordpress: writable
wp-content: writable
uploads: writable
plugins: writable
themes: writable
mu-plugins: writable

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Acceptance criteria

Implementation brief

QA testing instructions

Demo

Changelog entry

[westonruter]

Is a CSS post-processor enabled (SASS or LESS)?

As for the error message, I have todos to improve in subsequent PRs to #3780.

[westonruter]

Is this still an issue after the changes to fetching remote stylesheets?