Rails 5.2 asset helpers not including fingerprint digests - ruby-on-rails

Question

I am in the process of upgrading our product from rails 4.1 to 5.2. I'm hung up on what appears to be an asset pipeline related issue. When I load the app in our browser, I see the following error in the server log and the app is missing all styling and javascript code that it normally has.
DEPRECATION WARNING: The asset application.js" is not present in the asset pipeline.Falling back to an asset that may be in the public folder.
This behavior is deprecated and will be removed.
To bypass the asset pipeline and preserve this behavior,
use the `skip_pipeline: true` option.
When I wget the index.html of the application, I see that all of the images and javascript urls are lacking the fingerprint digest they should have. Interestingly enough, they do have the S3 asset_host we have, so they are in fact being processed by the helpers.
To demonstrate, I have two servers which have identical configurations, but one is running 4.1 and the other 5.2. On both, I am using S3 as an asset_host and digest is turned on. I've run the following commands in their consoles:
=== Rails 4 ===
Loading qatest environment (Rails 4.1.0)
irb(main):001:0> Rails.application.config.action_controller.asset_host
=> "https://redacted.s3.amazonaws.com"
irb(main):002:0> Rails.application.config.assets.digest
=> true
irb(main):003:0> ActionController::Base.helpers.asset_path('application.js')
=> "https://redacted.s3.amazonaws.com/assets/application-042f2014ca329c79c304ab1332557040d3f7b922247202f40c28acc950f30ef8.js"
=== Rails 5 ===
Loading sean environment (Rails 5.2.1)
irb(main):001:0> Rails.application.config.action_controller.asset_host
=> "https://redacted.s3.amazonaws.com"
irb(main):002:0> Rails.application.config.assets.digest
=> true
irb(main):003:0> ActionController::Base.helpers.asset_path('application.js')
=> "https://redacted.s3.amazonaws.com/application.js
As requested, production.rb
require "#{File.dirname(__FILE__)}/includes/s3_assets"
Rails.application.configure do
# Settings specified here will take precedence over those in config/application.rb
config.eager_load = true
# In the development environment your application's code is reloaded on
# every request. This slows down response time but is perfect for development
# since you don't have to restart the web server when you make code changes.
config.cache_classes = false
# Log error messages when you accidentally call methods on nil.
config.whiny_nils = false
config.log_level = ENV['SHOW_SQL'] != 'false' ? :debug : :info
# Show full error reports and disable caching
config.consider_all_requests_local = true
config.action_controller.perform_caching = false
config.action_mailer.raise_delivery_errors = true
config.action_mailer.perform_deliveries = true
config.action_mailer.delivery_method = :smtp
config.action_mailer.smtp_settings = {
user_name: Rubber.config.email_username,
password: Rubber.config.email_password,
address: Rubber.config.email_server,
port: Rubber.config.email_port,
enable_starttls_auto: true, # detects and uses STARTTLS
authentication: 'login' # Mandrill supports 'plain' or 'login'
}
# Print deprecation notices to the Rails logger
config.active_support.deprecation = :log
# Only use best-standards-support built into browsers
config.action_dispatch.best_standards_support = :builtin
# Raise exception on mass assignment protection for Active Record models
# config.active_record.mass_assignment_sanitizer = :strict
# Log the query plan for queries taking more than this (works
# with SQLite, MySQL, and PostgreSQL)
# config.active_record.auto_explain_threshold_in_seconds = 0.5
# Compress JavaScripts and CSS
config.assets.compress = true
# Don't fall back to assets pipelin if a precompiled asset is
# missed.
config.assets.compile = false
# Generate digests for assets URLs
config.assets.digest = true
config.assets.enabled = true
# Nginx will serve as an asset proxy to s3, where assets are
# stored.
config.serve_static_assets = false
# instead of bundling the assets, include multiple css style includes
config.assets.debug = true
config.assets.logger = false
# Enable serving of images, stylesheets, and JavaScripts from an asset server
# NB: The exclusion of any protocol in the asset host declaration above will allow browsers to choose the transport mechanism on the fly.
# So if your application is available under both HTTP and HTTPS the assets will be served to match.
configure_s3_assets config
config.action_controller.asset_host = "https://#{Rubber.config.s3_assets_bucket}.s3.amazonaws.com"
config.action_mailer.default_url_options = { :host => Rubber.config.external_host }
config.sequel.search_path = %w(public audit)
end
config/initializers/assets.rb
# Be sure to restart your server when you modify this file.
# Version of your assets, change this if you want to expire all your assets.
Rails.application.config.assets.version = '1.0'
# Add additional assets to the asset load path
# Rails.application.config.assets.paths << Emoji.images_path
# Precompile additional assets.
# application.js, application.css, and all non-JS/CSS in app/assets folder are already added.
# Rails.application.config.assets.precompile += %w( search.js )
Rails.application.config.assets.precompile += %w( *.js *.png *.eot *.woff *.ttf *.svg *.gif)
config/environments/includes/s3_assets.rb
def configure_s3_assets(config)
# Do not compress assets
config.assets.compress = false
# Disable Rails's static asset server (Apache or nginx will already do this)
config.serve_static_assets = false
# Generate digests for assets URLs
config.assets.digest = true
config.assets.enabled = true
# Precompile additional assets (application.js, application.css, and all non-JS/CSS are already added)
config.assets.precompile += %w(
)
# find javascripts/ stylesheets/ -type f | sed 's/\.scss//' | sed 's/\.coffee//' |
# sed 's/^.*\/\///'| sort
# defaults to application.js, application.css
# application.css has home.css ?
config.assets.precompile += %w(
handlebars.js
jquery-1.7.js
json2.js
)
end

Answer 1

After digging around in the sprockets code, I discovered that my list of resolvers was empty. I'm not sure what was missing from my configuration, but I fixed the problem by adding the following to config/application.rb
config.assets.resolve_with = [:manifest] // in production
config.assets.resolve_with = [:manifest, :environment] // in development