module ActionController
# Handles implicit rendering for a controller action that does not
# explicitly respond with +render+, +respond_to+, +redirect+, or +head+.
#
# For API controllers, the implicit response is always 204 No Content.
#
# For all other controllers, we use these heuristics to decide whether to
# render a template, raise an error for a missing template, or respond with
# 204 No Content:
#
# First, if we DO find a template, it's rendered. Template lookup accounts
# for the action name, locales, format, variant, template handlers, and more
# (see +render+ for details).
#
# Second, if we DON'T find a template but the controller action does have
# templates for other formats, variants, etc., then we trust that you meant
# to provide a template for this response, too, and we raise
# <tt>ActionController::UnknownFormat</tt> with an explanation.
#
# Third, if we DON'T find a template AND the request is a page load in a web
# browser (technically, a non-XHR GET request for an HTML response) where
# you reasonably expect to have rendered a template, then we raise
# <tt>ActionView::UnknownFormat</tt> with an explanation.
#
# Finally, if we DON'T find a template AND the request isn't a browser page
# load, then we implicitly respond with 204 No Content.
module ImplicitRender
# :stopdoc:
include BasicImplicitRender
def default_render(*args)
if template_exists?(action_name.to_s, _prefixes, variants: request.variant)
render(*args)
elsif any_templates?(action_name.to_s, _prefixes)
message = "#{self.class.name}\##{action_name} is missing a template " \
"for this request format and variant.\n" \
"\nrequest.formats: #{request.formats.map(&:to_s).inspect}" \
"\nrequest.variant: #{request.variant.inspect}"
raise ActionController::UnknownFormat, message
elsif interactive_browser_request?
message = "#{self.class.name}\##{action_name} is missing a template " \
"for this request format and variant.\n\n" \
"request.formats: #{request.formats.map(&:to_s).inspect}\n" \
"request.variant: #{request.variant.inspect}\n\n" \
"NOTE! For XHR/Ajax or API requests, this action would normally " \
"respond with 204 No Content: an empty white screen. Since you're " \
"loading it in a web browser, we assume that you expected to " \
"actually render a template, not nothing, so we're showing an " \
"error to be extra-clear. If you expect 204 No Content, carry on. " \
"That's what you'll get from an XHR or API request. Give it a shot."
raise ActionController::UnknownFormat, message
else
logger.info "No template found for #{self.class.name}\##{action_name}, rendering head :no_content" if logger
super
end
end
def method_for_action(action_name)
super || if template_exists?(action_name.to_s, _prefixes)
"default_render"
end
end
private
def interactive_browser_request?
request.get? && request.format == Mime[:html] && !request.xhr?
end
end
end
