discourse/lib/middleware/turbo_dev.rb

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# frozen_string_literal: true
module Middleware
# Cheat and bypass Rails in development mode if the client attempts to download a static asset
# that's already been downloaded.
#
# Also ensures that assets are not cached in development mode. Around Chrome 29, the behavior
# of `must-revalidate` changed and would often not request assets that had changed.
#
# To use, include in your project and add the following to development.rb:
#
# require 'middleware/turbo_dev'
# config.middleware.insert 0, Middleware::TurboDev
#
class TurboDev
def initialize(app, settings = {})
@app = app
end
def call(env)
root = "#{GlobalSetting.relative_url_root}/assets/"
is_asset = env["REQUEST_PATH"] && env["REQUEST_PATH"].starts_with?(root)
# hack to bypass all middleware if serving assets, a lot faster 4.5 seconds -> 1.5 seconds
if (etag = env["HTTP_IF_NONE_MATCH"]) && is_asset
name = env["REQUEST_PATH"][(root.length)..-1]
etag = etag.gsub "\"", ""
asset = Rails.application.assets.find_asset(name)
return 304, {}, [] if asset && asset.digest == etag
end
status, headers, response = @app.call(env)
headers["Cache-Control"] = "no-cache" if is_asset
[status, headers, response]
end
end
end