require 'active_support/core_ext/string/strip'
module ActionController
# Handles implicit rendering for a controller action when it did not
# explicitly indicate an appropiate response via methods such as +render+,
# +respond_to+, +redirect+ or +head+.
#
# For API controllers, the implicit render always renders "204 No Content"
# and does not account for any templates.
#
# For other controllers, the following conditions are checked:
#
# First, if a template exists for the controller action, it is rendered.
# This template lookup takes into account the action name, locales, format,
# variant, template handlers, etc. (see +render+ for details).
#
# Second, if other templates exist for the controller action but is not in
# the right format (or variant, etc.), an <tt>ActionController::UnknownFormat</tt>
# is raised. The list of available templates is assumed to be a complete
# enumeration of all the possible formats (or variants, etc.); that is,
# having only HTML and JSON templates indicate that the controller action is
# not meant to handle XML requests.
#
# Third, if the current request is an "interactive" browser request (the user
# navigated here by entering the URL in the address bar, submiting a form,
# clicking on a link, etc. as opposed to an XHR or non-browser API request),
# <tt>ActionView::UnknownFormat</tt> is raised to display a helpful error
# message.
#
# Finally, it falls back to the same "204 No Content" behavior as API controllers.
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} does not know how to respond " \
"to this request. There are other templates available for this controller " \
"action but none of them were suitable for this request.\n\n" \
"This usually happens when the client requested an unsupported format " \
"(e.g. requesting HTML content from a JSON endpoint or vice versa), but " \
"it might also be failing due to other constraints, such as locales or" \
"variants.\n"
if request.formats.any?
message << "\nRequested format(s): #{request.formats.join(", ")}"
end
if request.variant.any?
message << "\nRequested variant(s): #{request.variant.join(", ")}"
end
raise ActionController::UnknownFormat, message
elsif interactive_browser_request?
message = "You did not define any templates for #{self.class.name}\##{action_name}. " \
"This is not necessarily a problem (e.g. you might be building an API endpoint " \
"that does not require any templates), and the controller would usually respond " \
"with `head :no_content` for your convenience.\n\n" \
"However, you appear to have navigated here from an interactive browser request – " \
"such as by navigating to this URL directly, clicking on a link or submitting a form. " \
"Rendering a `head :no_content` in this case could have resulted in unexpected UI " \
"behavior in the browser.\n\n" \
"If you expected the `head :no_content` response, you do not need to take any " \
"actions – requests coming from an XHR (AJAX) request or other non-browser clients " \
"will receive the \"204 No Content\" response as expected.\n\n" \
"If you did not expect this behavior, you can resolve this error by adding a " \
"template for this controller action (usually `#{action_name}.html.erb`) or " \
"otherwise indicate the appropriate response in the action using `render`, " \
"`redirect_to`, `head`, etc.\n"
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.format == Mime[:html] && !request.xhr?
end
end
end
