In Rails, how do I override the format from the URL - ruby-on-rails

Question

I have a report that's available in HTML or PDF formats. Sometimes, I want to display an error message instead of the report. The error message should be wrapped in my application's usual layout.
This works fine if the request was for the HTML report, but if the PDF report was requested, I get "There was no default layout for MyController in #<ActionView::PathSet..."
My controller method looks like this:
def report
unless report_available?
render html: '<div class="error">Not available.</div>'.html_safe,
:status => 404, :layout => true
return
end
...
end
I've tried adding :formats => :html or :formats => [:html] to the call to render, but it has no effect. I've also tried setting params[:format] = 'html' before calling render, but that didn't help either.
How do I render a snippet of HTML using the default layout when the request was for report.pdf?
The full error message looks like:
There was no default layout for MyController in #<ActionView::PathSet:0x00007fd3b842c370 #paths=[#<ActionView::OptimizedFileSystemResolver:0x00007fd3d0776c20 #pattern=":prefix/:action{.:locale,}{.:formats,}{+:variants,}{.:handlers,}", #cache=#<ActionView::Resolver::Cache:0x7fd3d0776bf8 keys=1 queries=0>, #path="/var/www/apps/myapp/releases/1/app/views">]>
And the stack trace looks like:
actionview (5.1.6) lib/action_view/layouts.rb:420:in `_default_layout'
actionview (5.1.6) lib/action_view/layouts.rb:389:in `block in _layout_for_option'
actionview (5.1.6) lib/action_view/renderer/template_renderer.rb:94:in `resolve_layout'
actionview (5.1.6) lib/action_view/renderer/template_renderer.rb:74:in `find_layout'
actionview (5.1.6) lib/action_view/renderer/template_renderer.rb:58:in `render_with_layout'
actionview (5.1.6) lib/action_view/renderer/template_renderer.rb:50:in `render_template'
actionview (5.1.6) lib/action_view/renderer/template_renderer.rb:14:in `render'
actionview (5.1.6) lib/action_view/renderer/renderer.rb:42:in `render_template'
actionview (5.1.6) lib/action_view/renderer/renderer.rb:23:in `render'
actionview (5.1.6) lib/action_view/rendering.rb:103:in `_render_template'
actionpack (5.1.6) lib/action_controller/metal/streaming.rb:217:in `_render_template'
actionview (5.1.6) lib/action_view/rendering.rb:83:in `render_to_body'
actionpack (5.1.6) lib/action_controller/metal/rendering.rb:52:in `render_to_body'
actionpack (5.1.6) lib/action_controller/metal/renderers.rb:141:in `render_to_body'
actionpack (5.1.6) lib/abstract_controller/rendering.rb:24:in `render'
actionpack (5.1.6) lib/action_controller/metal/rendering.rb:36:in `render'
actionpack (5.1.6) lib/action_controller/metal/instrumentation.rb:44:in `block (2 levels) in render'
activesupport (5.1.6) lib/active_support/core_ext/benchmark.rb:12:in `block in ms'
/usr/local/rbenv/versions/2.4.3/lib/ruby/2.4.0/benchmark.rb:308:in `realtime'
activesupport (5.1.6) lib/active_support/core_ext/benchmark.rb:12:in `ms'
actionpack (5.1.6) lib/action_controller/metal/instrumentation.rb:44:in `block in render'
actionpack (5.1.6) lib/action_controller/metal/instrumentation.rb:87:in `cleanup_view_runtime'
activerecord (5.1.6) lib/active_record/railties/controller_runtime.rb:29:in `cleanup_view_runtime'
actionpack (5.1.6) lib/action_controller/metal/instrumentation.rb:43:in `render'
app/controllers/my_controller.rb:809:in `report'
I believe the problem is that it's looking for a layout with .pdf.erb instead of .html.erb, but I don't know how to change that.

Answer 1

What you need to do is redirect to 404 page with this as a flash notice.
If you don't have a 404 page, you'd need one anyway.

Answer 2

You have to set the request format of your action:
def report
request.format = :html
# ..
end
You can also use it in a before_action filter
class ApplicationController < ActionController::Base
before_action :set_default_response_format
protected
def set_default_response_format
request.format = :html
end
end