proposition

gistfile1.txt

Initial problem:

	use Mojolicious::Lite;
	use Test::Mojo;
	use Test::More;

	get '/test' => { format => 'xxx' };

	my $t = Test::Mojo->new;

	$t->get_ok('/test')->content_is( "xxx\n" );
	$t->get_ok('/test.json')->content_is( "json\n" );
	$t->get_ok('/test?format=json')->content_is( "json\n" );

	done_testing();

	__DATA__
	@@ test.xxx.ep
	xxx

	@@ test.json.ep
	json




	$ perl basic.t
	ok 1 - GET /test
	ok 2 - exact match for content
	ok 3 - GET /test.json
	ok 4 - exact match for content
	ok 5 - GET /test?format=json
	not ok 6 - exact match for content
	#   Failed test 'exact match for content'
	#   at basic.t line 11.
	#          got: 'xxx
	# '
	#     expected: 'json
	# '
	1..6
	# Looks like you failed 1 test of 6.

As you can see default stash value for {format} take precedence over format
query parameter.


Whithout splitting out {format} default stash value
from {format} requested by client
we can not do proper content negotiation:

    https://github.com/kraih/mojo/blob/v7.50/lib/Mojolicious/Renderer.pm#L31

Notice: this is v7.50


I propose that splitting in next patch:

    https://github.com/KES777/mojo/pull/36/files#diff-2650135fc08c671d8b875d9b8480f498

This will allow better fallbacks for content negotiation when html is not
the default. I'm proposing an array ref valued stash parameter
which could take that into account. Example:

    https://github.com/KES777/mojo/pull/36/files#diff-08d2a3a980946f364c7bf445ea6d4a2cR114


  # Restrict all controllers to given format:
  # /hello                      -> "html"
  # /hello (Accept: text/html)  -> "html"
  # /hello (Accept: text/xml)   -> "xml"
  # /hello (Accept: text/plain) -> undef
  # /hello.html                 -> "html"
  # /hello.xml                  -> "xml"
  # /hello.txt                  -> undef
  # /hello?format=html          -> "html"
  # /hello?format=xml           -> "xml"
  # /hello?format=txt           -> undef
  $app->plugin('Format');
  $app>defaults( format => [qw( html xml )] );

  # Or only current route:
  # /custom                      -> "json"
  # /custom.html                 -> undef
  # /custom.xml                  -> "xml"
  # /custom.txt                  -> undef
  $r->get( '/custom', { format => [qw( json, xml )] );

  # Same but in controller's action (fallback is disabled):
  # /action                      -> undef
  # /action.html                 -> "html"
  # /action.xml                  -> "xml"
  # /action.txt                  -> undef
  my $format = $c->format(undef, 'html', 'xml');

Personally I prefer: $c->format('', 'html', 'xml'); (as accepts do) but in this case the ''empty string will be returned. To be consistent we need to return '' empty string instead of undef for other cases too

I can not decide which variant is better, so it is up to you.